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Turtle and Dugong Monitoring End of Dredging Report

Ichthys Nearshore Environmental Monitoring Program L384-AW-REP-10249

3.6 and Grid 16 = 5.81

Prepared for INPEX September 2014

Turtle and Dugong Monitoring End of Dredging Report

Ichthys Nearshore Environmental Monitoring Program L384-AW-REP-10249

Turtle and Dugong Monitoring End of Dredging Report Ichthys Nearshore Environmental Monitoring Program

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Document Information Prepared for INPEX Project Name Ichthys Nearshore Environmental Monitoring Program File Reference L384-AW-REP-10249_0_Turtle and Dugong End of Dredging Report.docm Job Reference L384-AW-REP-10249 Date September 2014

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Document Control Version Date Author Author

Initials Reviewer Reviewer

Initials

A 05/08/2014 Michelle Blewitt Freya Muller Andrea Nicastro Ivon Sebastian

MLB FM AN IS

Craig Blount Will Macbeth Joanna Lamb

CB WMc JL

B 28/08/2014 Ivon Sebastian Freya Muller

IS FM

Craig Blount Joanna Lamb

CB JL

0 02/09/2014 Michelle Blewitt MB Joanna Lamb JL

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Executive Summary The Turtle and Dugong Monitoring Program (TDMP) has been developed to monitor patterns of distribution and abundance of turtles and dugongs around Darwin Harbour and surrounding inshore waters during dredging and spoil disposal activities associated with the Ichthys Gas Field Development Project (the Project). The program uses aerial surveys in one location potentially affected by construction (Darwin Harbour/Hope Inlet region (Impact location – IM)), and at two additional Control locations (Bynoe Harbour (Control location 1 – C1) and the Vernon Islands, across to Melville Island (Control location 2 – C2)). Furthermore, to supplement the aerial survey data, observations of turtles and dugongs have also been made at two ‘hotspots’ within IM (Channel Island Bridge and Cullen Bay rock wall), and satellite tags have been attached to four juvenile green turtles captured and released at Channel Island during the TDMP and one adult hawksbill turtle released at Nightcliff to investigate patterns of movement.

Monitoring for the TDMP has occurred routinely during the Dredging Phase of the Project, and data has been compared with those collected prior to the commencement of dredging (Baseline Phase). Monitoring during the Dredging Phase has included surveys following Season One dredging operations during the 2013 dry season dredging hiatus (D2: May 2013, D3: July 2013, D4: October 2013) and during Gas Export Pipeline (GEP) dredging operations and Season Two East Arm (EA) dredging during the 2014 dry season (D5: May 2014). D5 is the final survey of the Dredging Phase and was undertaken between 9 May 2014 and 25 May 2014, approximately five-and-a-half months following the commencement of GEP dredging operations (23 October 2013) and Season Two EA dredging operations (1 November 2013). East Arm dredging was completed during the D5 survey. This End of Dredging Report provides a description and interpretation of the results from D5, and a summary of all Dredging Phase results collected as part of the TDMP to date.

During the monitoring program, there have been fluctuations among surveys in both raw sightings of dugongs and the estimates of abundance derived from these; however the fluctuations have generally been within the margin of error. No trends (including seasonal) have been evident, suggesting that abundance fluctuates about a mean at all three locations. Raw counts in particular show that, overall, comparable numbers of dugongs were sighted during the Baseline Phase and at the completion of Dredging Phase surveys. Estimates of dugong abundance at the three locations during the Baseline Phase ranged between 157 and 411 dugongs (as estimated using the Marsh and Sinclair (1989) method) or between 95 and 273 dugongs (as estimated using the Pollock et al. (2006) method). During the Dredging Phase, estimates ranged between 93 and 382 dugongs, or between 41 and 274 dugongs, depending on the method. There was a higher frequency of dugong sightings in shallow regions (6 m to 10 m water depth) within all three locations. Very few dugongs have been sighted within Darwin Harbour Inner in either the Baseline or Dredging Phases. The observed variability in dugong sightings among replicate aerial flights and among surveys, along with spatial patterns in abundance within locations, probably resulted from a number of factors including short-term movement of dugongs in search of optimum foraging areas, and seasonal variation in the density and distribution of seagrass which is the primary food source for dugongs.

Turtle sightings were more widespread than those of dugongs, with turtles observed in relatively large numbers in all three locations over the duration of the monitoring program. Similar to dugongs, there was temporal and spatial variation in estimates of turtle abundance. Although there were fluctuations between surveys in raw sightings, the number of sightings for each survey was within the margin of error. For all three locations, no temporal trends were evident suggesting that, similar to dugongs, abundance at all three locations fluctuates about a mean. Estimates of turtle abundance at the three locations during the Baseline Phase ranged between 335 and 1,469 turtles using the Marsh and Sinclair (1989) method) and, similarly, between 350 and 1,437 turtles using the Pollock et al. (2006) method. During the Dredging Phase, estimates ranged between 412 and 1,013 turtles or between 433 and 1,030 turtles, depending upon the method. Sightings of turtles during both the Baseline and Dredging Phases were generally lower in the IM block compared to the Control locations. Differences between locations and fluctuations between surveys may have been due to a combination of factors including movement of turtles in search of optimum foraging areas and, for some of the areas, potentially the influx of nesting turtles at certain times. In addition, variable environmental conditions such as water clarity and Beaufort Sea State at the time of the survey may also have influenced turtle sightings.


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Green turtle has been the predominant species reported in boat- and land-based surveys. In the aerial surveys turtles were also regularly sighted in areas further offshore in all three locations, although species were not able to be identified due to the observation distance. Available evidence suggests the four juvenile green turtles tagged and released at Channel Island during the TDMP remained in the vicinity for the duration of satellite tag transmissions (i.e. up to 168 days), staying within a small range of between approximately 1 km2 and 1.5 km2. The tagged juvenile green turtles appeared to utilise discrete shallow habitats around Channel Island, including areas of reef and mangroves, while the tagged adult hawksbill turtle has predominantly remained in deeper waters.

In summary, while spatial and temporal variation has been observed in the distribution and abundance of turtles and dugongs over the duration of the TDMP, on the balance of evidence these differences appear most likely due to natural variation. As such, following the completion of the Dredging Phase of monitoring, there is no indication of any major changes to turtle or dugong populations in the Darwin region as a result of dredging activities.


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Glossary

Term or Acronym Definition

Availability bias A bias in the data affected by an animal being concealed by an environmental factor so that is not visible to the observer

ACF Availability Correction Factor

AFMA Australian Fisheries Management Authority

B1 Baseline Phase survey 1: 1 June 2012 to 8 June 2012 (2 replicate flights)

B2 Baseline Phase survey 2: 18 July 2012 to 5 August 2012 (3 replicate flights)

B3 Baseline Phase survey 3: 30 September 2012 to 21 October 2012 (3 replicate flights)

BACI Before, After, Control, Impact

BHD Backhoe Dredger

BSS Beaufort Sea State is an empirical measure (0 to 12) for the intensity of the wind based mainly on sea-state or wave conditions, with 0 refering to calm, mirror like seas and 12 refers to hurricane conditions

C1 Control block 1 (Bynoe Harbour)

C2 Control block 2 (Vernon Islands to Melville Island)

CITES Convention on International Trade of Endangered Species

CSD Cutter Suction Dredger

CV Coefficient of Variation is used to compare the standard deviations between populations with different means and it provides a measure of variation that is independent of the measurement units

D1 Completed during Backhoe Dredger (BHD) operations only where impacts are considered minimal and thus D1 survey is referred to as Baseline survey 3 (B3)

D2 Dredging Phase survey 2: 11 May 2013 to 26 May 2013 (2 to 3 replicate flights)

D3 Dredging Phase survey 3: 27 July 2013 to 11 August 2013 (3 replicate flights)

D4 Dredging Phase survey 4: 11 October 2013 to 27 October 2013 (3 replicate flights)

D5 End of Dredging Phase survey 5:9 May 2014 to 25 May 2014 (2 to 3 replicate flights)


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DLRM Department of Land Resource Management

Double platform

A sampling method using two observers to sample a given species in the same area at the same time. The two observers must be independent of each other and isolated visually and acoustically. On aerial surveys, the two observers are normally arranged as a front and rear observer

DSDMP Dredging and Spoil Disposal Management Plan

EA East Arm

EPBC Act Environment Protection and Biodiversity Conservation Act 1999

GEP Gas export pipeline

GIS Geographic Information System

Group size Mean group size of a group of dugongs or turtles observed during aerial surveys

IM Impact block (Darwin Harbour/Hope Inlet to Gunn Point)

IUCN International Union for the Conservation of Nature

LC Location Class

Megafauna Description of large marine fauna, e.g. turtles, dugongs, dolphins

MSL Mean Sea Level

n Sample size

NEMP Nearshore Environmental Monitoring Plan

NT Northern Territory

NTC National Tidal Centre

PB Port observers – both front and rear

PCF Perception Correction Factor

Perception bias A bias in the data caused by an observer not seeing an animal despite it being visible

PERMANOVA Permutational Analysis of Variance

PF Port observer – front only

Population estimate An estimate of the number of individual animals living in one place at the one time

p-perm Equivalent to the traditional p-value but derived from a permutational analyses (PERMANOVA)


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PR Port observer – rear only

QA/QC Quality Assurance/Quality Control

Recapture The event of one individual or group of animals being counted (and thus recorded) a subsequent time, usually by the rear observer during aerial surveys

SB Starboard observers – both front and rear

SE Standard error of the mean

SF Starboard observer – front only

SR Starboard observer – rear only

TDMP Turtle and Dugong Monitoring Program

TPWCA Territory Parks and Wildlife Conservation Act 2001

Turbidity Turbidity is an indication of water clarity


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Table of Contents Executive Summary iii Glossary v

1 Introduction 1 1.1 Overview 1 1.2 Background 1 1.3 Summary of Baseline Phase Sampling Results 2 1.4 Objectives 2

2 Methodology 3 2.1 Field Monitoring Schedule 3 2.2 Field Sampling Locations 5

2.2.1 Aerial Surveys 5 2.2.2 Land Surveys 5 2.2.3 Turtle Tagging 5

2.3 Field Methods 8 2.3.1 Monitoring Permits 8 2.3.2 Aerial Surveys 8 2.3.3 Land Surveys 9 2.3.4 Turtle Tagging 10

2.4 Assumptions and Constraints 11 2.4.1 Aerial Surveys 11 2.4.2 Land Surveys 11 2.4.3 Turtle Tagging 11

2.5 Data Analysis 12 2.5.1 Aerial Surveys 12 2.5.2 Land Surveys 14 2.5.3 Turtle Tagging 14

2.6 Quality Assurance/Quality Control (QA/QC) 14

3 Dredging Operations 15

4 Results 17 4.1 Aerial Surveys 17

4.1.1 Survey Effort and Environmental Conditions 17 4.1.2 Dugongs 17 4.1.3 Turtles 35

4.2 Land Surveys 56 4.2.1 Survey Effort and Environmental Conditions 56 4.2.2 Channel Island Bridge 56 4.2.3 Cullen Bay Rock Wall 56

4.3 QA/QC for Aerial and Land Surveys 59 4.4 Turtle Tagging 59

4.4.1 Turtles Tagged 59 4.4.2 Ranges and Patterns of Movements of Tagged Turtles 59 4.4.3 Depth and Duration of Turtle Dives 64 4.4.4 Rehabilitated Turtles 65

5 Discussion 68 5.1 Dugongs 68


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5.2 Turtles 69

6 Conclusion 71

7 Acknowledgements 72

8 References 73

Tables Table 2-1 Monitoring schedule for the TDMP 4 Table 3-1 Dredge footprint summary 15 Table 4-1 Details of group size estimates and correction factors used in dugong population estimates for

D5 (May 2014) aerial surveys 27 Table 4-2 Sighting histories for dugong groups sighted during D5 aerial surveys by individual observers for

all flights combined* 28 Table 4-3 Comparison of dugong population estimates (± SE) and number of replicates where estimates

were able to be derived (n) for: a) each block during B1, D2 and D5; and b) across Baseline and Dredging Phases, based on Marsh and Sinclair (1989) and Pollock et al. (2006) 29

Table 4-4 Results of univariate PERMANOVA tests for differences in the density of dugongs per km2 based on: a) the Marsh and Sinclair (1989) method; b) the Pollock et al. (2006) method; and c) raw sightings between two Phases (Baseline and Dredging), including Phase (B1, B2 and B3 within Baseline Phase; and D2, D3, D4 and D5 within Dredging Phase), two Treatments (Control and Impact) and three Blocks (C1 and C2 within Control; and IM within Impact) 34

Table 4-5 Details of turtle group size estimates for whole blocks and correction factors used in population estimates for the D5 aerial surveys 44

Table 4-6 Sighting histories for turtles sighted during D5 aerial surveys by individual observers for each replicate flight, and all flights combined* 45

Table 4-7 Comparison of turtle population estimates (± SE) and number of replicates where estimates were able to be derived (n) for: a) each block during B1 (May 2012), D2 (May 2013) and D5 (May 2014); and b) across the Baseline and Dredging Phases, based on Marsh and Sinclair (1989) and Pollock et al. (2006) 46

Table 4-8 Results of univariate PERMANOVA tests for differences in the density of turtles per km2 based on: a) Marsh and Sinclair (1989); b) Pollock et al. (2006); and c) raw sightings between two Phases (Baseline and Dredging), including Phase (B1, B2 and B3 within Baseline Phase; and D2, D3, D4 and D5 within Dredging Phase), two Treatments (Control and Impact) and three Blocks (C1 and C2 within Control; and IM within Impact) 51

Table 4-9 Turtle population estimates (± SE) for each sub-block during D5 (May 2014) based on Marsh and Sinclair (1989) and Pollock et al. (2006), averaged across replicate flights 53

Table 4-10 Turtle density estimates (per km2) for each sub-block during D5 (May 2014) based on Marsh and Sinclair (1989) and Pollock et al. (2006) 54

Table 4-11 Survey effort for land surveys during D5 (May 2013) 56 Table 4-12 Number of megafauna sightings and number of individual animals observed at Channel Island

Bridge and Cullen Bay rock wall during D5 (May 2014) land surveys 57 Table 4-13 Total number of megafauna sightings observed at Channel Island Bridge and Cullen Bay rock

wall during all Dredging Phase land surveys (D2, D3, D4 and D5) N.B. Counts are of total sightings, not individuals. Land surveys were not undertaken during the Baseline Phase (2012)57

Table 4-14 Summary of juvenile turtles captured during the November 2013 and December 2013 tagging events 59


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Figures Aerial survey blocks and sub-divisions encompassing Bynoe Harbour (C1), Darwin Figure 2-1

Harbour/Hope Inlet region (IM) and Vernon Islands (C2) 6 Land survey sites in Darwin Harbour during D5 (May 2014):Cullen Bay rock wall (left); and Figure 2-2

Channel Island Bridge (right), also showing the turtle tagging site 7 Plane window calibration for aerial surveys (top dotted line = Very High; bottom dotted line = Figure 2-3

Low) 9 Tagged sub-adult green turtle, ‘Pepin’, caught November 2013 (see Section 4.4.1) 10 Figure 2-4 Distribution of dugongs (based on raw sightings) among and within sub-blocks during D5 aerial Figure 4-1

surveys (three replicate flights) 19 Mean counts per replicate (± SE) of dugongs sighted in each block (C1, IM and C2) for all aerial Figure 4-2

surveys completed to date (B1 (May 2012) to D5 (May 2014)) 20 Density of dugong sightings (based on raw counts) per km2 of transect area sampled over water Figure 4-3

within 6 km x 6 km grids at IM during D5 (May 2014) 21 Relative difference in dugong density (based on raw counts) per km2 of transect area sampled Figure 4-4

over water within 6 km x 6 km grids in IM during D5 (May 2014) compared with D2 (May 2013)22 Relative difference in the dugong density (based on raw counts) per km2 of transect area Figure 4-5

sampled over water within 6 km x 6 km grids at IM during D5 (May 2014) compared with B1 (May 2012) 23

Proportion of dugong sightings within different depth ranges (m) in: a) C1; b) IM; and c) C2 Figure 4-6during B1 (May 2012), D2 (May 2013) and D5 (May 2014) 25

Proportion of dugong sightings with respect to benthic habitat types at: a) C1; b) IM; and c) C2 Figure 4-7during B1 (May 2012), D2 (May 2013) and D5 (May 2014) 26

Mean population estimates for dugongs in each block across all surveys (B1 to D5), based on: Figure 4-8a) Marsh and Sinclair (1989) method; b) Pollock et al. (2006) method; and c) raw sightings data30

Mean dugong density per km2 (± SE) in each block during the TDMP across all surveys (B1 to Figure 4-9D5), based on: a) Marsh and Sinclair (1989) method; b) Pollock et al. (2006) method; and c) raw sightings 32

Dugong population density, averaged over all blocks, using the Marsh and Sinclair (1989) Figure 4-10method 33

Distribution of turtles (based on raw sightings) during the D5 (May 2014) aerial survey 36 Figure 4-11 Mean counts per replicate (± SE) of turtles sighted in each block (C1, IM and C2) for all aerial Figure 4-12

surveys to date from B1 (May 2012) to D5 (May 2014) 37 Density of turtle sightings (based on raw counts) per km2 of transect area sampled over water Figure 4-13

within 6 km x 6 km grids in IM during the D5 (May 2014) aerial survey 38 Relative difference in turtle density (based on raw counts) per km2 of transect area sampled Figure 4-14

over water within 6 km x 6 km grids in IM during the D5 (May 2014) aerial survey compared to B1 (May 2012) 39

Relative difference in the turtle density (based on raw counts) per km2 of transect area sampled Figure 4-15over water within 6 km x 6 km grids in IM during the D5 (May 2014) aerial survey compared to D2 (May 2013) 40

Proportion of turtle sightings observed within different depth ranges (m) in: a) C1; b) IM; and c) Figure 4-16C2 during the B1 (May 2012), D2 (May 2013) and D5 (May 2014) aerial surveys 42

Proportion of turtle sightings with respect to benthic habitat types in: a) C1; b) IM; and c) C2 Figure 4-17during the B1 (May 2012), D2 (May 2013) and D5 (May 2014) aerial surveys 43

Mean population estimates for turtles in each block during the TDMP across all surveys (B1 to Figure 4-18D5), based on: a) Marsh and Sinclair (1989); and b) Pollock et al. (2006) population estimate methodologies; and c) raw sightings data 47

Mean turtle density per km2 (± SE) in each block during the TDMP from B1 (May 2012) to D5 Figure 4-19(May 2014) based on: a) Marsh and Sinclair (1989); b) Pollock et al. (2006); and c) raw sightings data 49


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Mean population estimates (± SE) for turtles derived from whole block and sum of sub-block Figure 4-20calculations based on: a) Marsh and Sinclair (1989); and b) Pollock et al. (2006) at each location for D5 (May 2014) 55

Distribution of megafauna sighted during land surveys in D5 (May 2014) 58 Figure 4-21 Transmitted geo-locations of ‘Pepin’, satellite tagged on 6 November 2013. Dots indicate Figure 4-22

movement recorded between 6 November 2013 and 22 April 2014 61 Transmitted geo-locations of ‘Hendrix’, satellite tagged on 6 December 2013. The dots indicate Figure 4-23

movement patterns, recorded between 6 December 2013 and 13 March 2014 62 Transmitted geo-locations of ‘Chloe’, satellite tagged on 5 December 2013. The dots indicate Figure 4-24

movement patterns for data from 5 December 2013 to 4 March 2014 63 Proportion of dives for specific durations (min) for turtles tagged during the November 2013 and Figure 4-25

December 2013 tagging events 64 Proportion of dives for specific depths (m) for turtles tagged during the November 2013 and Figure 4-26

December 2013 tagging events 65 Proportion of dives at specific depths (m) for tagged rehabilitated turtle ‘Linh’ 66 Figure 4-27 Proportion of dives for specific durations (min) for tagged rehabilitated turtle ‘Linh’ 66 Figure 4-28 Transmitted geo-locations of ‘Linh’, satellite tagged on 27 March 2014. Dots indicate movement Figure 4-29

patterns recorded between 27 March 2014 and 10 June 2014 67

Appendices Appendix A Summary of Aerial Survey Effort During Baseline Phase and Dredging surveys Appendix B Summary of Dugong Sightings Across Dredging and Baseline Phase surveys Appendix C Summary of Turtle and Dugong Sightings Overlaid with Confirmed Seagrass Habitat During

B1, D2 and D5 Surveys Appendix D Dugong Population Size Estimates During Dredging and Baseline Phase Surveys Appendix E Corrected Dugong Densities During Dredging and Baseline Phase Surveys Appendix F Summary of Turtle Sightings Across Dredging and Baseline Phase Surveys Appendix G Turtle Population Size Estimates During Dredging and Baseline Phase Surveys Appendix H Corrected Turtle Densities During Dredging and Baseline Phase Surveys Appendix I Turtle Sub-block Population Size Estimates During D5 Aerial Surveys Appendix J Corrected Turtle Sub-block Densities During D5 Aerial Surveys Appendix K Land Survey Data During D5 Survey Appendix L Rehabilitated Turtle Summary Data


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1 Introduction

1.1 Overview INPEX is the operator of the Ichthys Gas Field Development Project (the Project). The Project comprises the development of offshore production facilities at the Ichthys Field in the Browse Basin, some 820 km west-south-west of Darwin and 450 km north-northeast of Broome, an 889 km long subsea gas export pipeline (GEP) and an onshore processing facility and product loading jetty at Bladin Point on Middle Arm Peninsula in Darwin Harbour. To support the nearshore infrastructure at Bladin Point, dredging works have been carried out to extend safe shipping access from near East Arm Wharf to the new product loading facilities at Bladin Point which are supported by piles driven into the sediment. A trench has also been dredged to seat and protect the GEP for the Darwin Harbour portion of its total length. Dredged material has been disposed at the spoil ground located approximately 12 km north-west of Lee Point. A detailed description of the dredging and spoil disposal methodology is provided in Section 2 of the East Arm (EA) Dredging and Spoil Disposal Management Plan (DSDMP) (INPEX 2013) and GEP DSDMP (INPEX 2014).

1.2 Background Following an Environmental Impact Assessment (INPEX 2011) the Project was approved subject to conditions that included monitoring for potential effects of dredging or spoil disposal on local ecosystems. Marine turtles and dugongs were included among the species to be monitored although the risk to populations within Darwin Harbour due to dredging and construction activities was considered minimal.

Dugongs are listed as ‘threatened with extinction’ under the Convention on International Trade of Endangered Species (CITES) and as ‘vulnerable to extinction’ in the International Union for the Conservation of Nature (IUCN) and Natural Resources Red Data Book of Threatened Species. In Australian waters, dugongs are listed as ‘migratory’ under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act).

Dugongs forage selectively on seagrass, their preferred diet, particularly tropical genera such as Halodule and Halophila (Preen 1992). Dugongs have also been sighted feeding on algal covered rocky reefs in the Darwin region (Whiting 2002). Calving occurs from late August to November and predominantly in protected shallow waters such as tidal sandbanks and estuaries (Marsh et al. 1999), although the reproductive rate of individuals is inconsistent (Lanyon 2007). In the Northern Territory, areas of critical habitat for conservation have been declared under Section 37 of the Territory Parks and Wildlife Conservation Act 2001 (TPWCA) but these are outside of the construction areas of the Project.

Of the six species of marine turtles known to be present in Australian waters, four are considered to occur around the Darwin region; these are green, hawksbill, olive ridley and flatback turtles. These species are listed as ‘threatened with extinction’ under CITES. In Australian waters, olive ridley turtles are listed as ‘endangered’, while green, hawksbill and flatback turtles are listed as ‘vulnerable’ under the EPBC Act.

All marine turtles have the same general life cycle. They grow slowly and take decades to reach sexual maturity. Between 20 and 50 years, males and females leave their feeding grounds and migrate up to 3,000 km to a nesting area located in the region of their birth. Green turtles (immature and adult) have been observed in both reef and non-reef habitats around the Darwin region (Whiting 2000). Within Darwin Harbour, green and hawksbill turtles are occasionally sighted near Channel Island, with green turtles also sighted near Weed Reef (Whiting 2000). Olive ridley turtles are rarely sighted in shallow waters and are known to occur only occasionally in Darwin Harbour (NAILSMA 2006). Flatback turtle is the most commonly encountered nesting species inside Darwin Harbour during the dry season (Chatto and Baker 2008). Casuarina Beach, a popular Darwin beach, has been monitored for nesting turtles since the mid-1990s (Chatto and Baker 2008).



1.3 Summary of Baseline Phase Sampling Results Baseline Phase aerial surveys (B1: May 2012, B2: July 2012, B3: October 2012) for the TDMP were carried out in an area encompassing Darwin Harbour/Hope Inlet to Gunn Point (Impact location – IM) and at two Control locations (Control location 1, to the west of IM – C1; and Control location 2, to the east of IM – C2), prior to the commencement of Cutter Suction Dredger (CSD) operations in EA (4 November 2012). Baseline Phase survey 3 (B3) was originally termed Dredging Phase survey 1 (D1) and undertaken after the commencement of the Backhoe Dredger (BHD) operations on 27 August 2012. However, given that this was prior to the start of the Cutter Suction Dredger (CSD), D1 was renamed B3. This reallocation of the survey into the Baseline Phase was further supported by statistical analyses comparing B1, B2 and B3, which found no statistical difference in abundance of dugongs (or turtles) between the three Baseline Phase surveys.

During the Baseline Phase, a total of 263 dugongs and 1,903 turtles were sighted. The average size of the dugong population in C1 was estimated to be 176 (± 67) dugongs during B1, 287 (± 65) dugongs during B2 and 157 (± 118) dugongs during B3. Estimates of population size made for C2 were similar to those made for C1. The highest population estimates were associated with the IM block, with 243 (± 67) dugongs during B1, 411 (± 139) dugongs during B2 and 401 (± 185) dugongs during B3. Spatial and temporal estimates of dugong density, based on calculations of corrected data, followed closely the patterns obtained for population size. In C1, densities ranged from 0.34 dugongs/km2 in B2 to 0.20 dugongs/km2 in B3, while estimates for C2 were similar. The greatest densities of dugongs were observed in the IM block during B3, at 0.35 dugongs/km2.

The total number of turtles sighted during B3 (n = 984) was considerably higher than for B1 (n = 334) or B2 (n = 585). Population size estimates for turtles varied among surveys and locations, though not significantly among surveys. In C1, Baseline Phase population estimates were 335 ± 47 turtles during B1, 1,333 ± 213 turtles during B2, and 778 ± 174 turtles in B3. Results were similar for C2. Comparable to dugongs, population sizes of turtles were greatest in the IM block, with 739 ± 188 turtles in B1, 1,469 ± 369 turtles in B2, 868 ± 124 turtles in B3. The full Baseline Phase results of the TDMP are reported in the Turtle and Dugong Monitoring Program Baseline Report (Cardno 2012).

1.4 Objectives The key objectives of the TDMP are to:

> Quantify the variability of turtle and dugong relative abundance and distribution in the inshore waters of Darwin Harbour and nearshore waters between and within surveys. Observe changes in these parameters over the duration of the Dredging and Post Dredging Phases; and

> Assess fine scale aspects of dugong and turtle populations within Darwin Harbour in relation to potential habitat use and identify foraging areas (if possible).

This report focuses on results from the end of Dredging Phase aerial and land surveys (D5; May 2014), and updated results for the turtle tagging events undertaken in late 2013. Where appropriate, comparisons were made with aerial and land survey data recorded during Baseline Phase (B1 (May 2012), B2 (July 2012) and B3 (October 2012)) and Dredging Phase (D2 (May 2013), D3 (July 2013) and D4 (October 2013) surveys.



2 Methodology

Specific details on the methodology used in the TDMP for aerial surveys are described in Appendix K of the Nearshore Environmental Monitoring Plan (NEMP; Rev 4) (Cardno 2013a) and the TDMP Baseline Report. Turtle tagging methods are outlined in the Dredging Report 1 (Cardno 2012, 2013b). Where methodology has been refined, or where additional analyses have been utilised, details are provided in this report.

2.1 Field Monitoring Schedule Table 2-1 outlines the monitoring schedule for the TDMP during the Baseline and Dredging Phases. Aerial surveys were undertaken during all Baseline and Dredging Phase surveys during the dry season. The dry season is the optimal time of the year to undertake aerial surveys due to limited visibility in rainy conditions and the need for near perfect conditions for successful surveys.

Boat surveys (transect and point sampling) were carried out during the Baseline Phase (B1 to B3) only, while land surveys (point sampling) were undertaken during all Dredging Phase surveys (D2 to D5), in accordance with the NEMP (Cardno 2013a).

Turtle satellite tagging was initially undertaken in October 2012 and November 2012 at Channel Island and in October 2012 at Casuarina Beach, where an attempt was made to tag nesting flatback turtles. Further successful tagging events were undertaken at Channel Island in November 2013 and December 2013.



Table 2-1 Monitoring schedule for the TDMP

Sampling Periods

Baseline Phase Dredging Phase

Field Method Site B1 B2 B3 D2 D3 D4 D5

Aerial surveys

Darwin Harbour and surrounding waters

May 2012 2 replicate flights (C1, IM, C2)

July 2012 3 replicate flights (C1, IM, C2)

October 2012 3 replicate flights (C1, IM, C2)

May 2013 3 replicate flights (C1, IM) 2 replicate flights (C2)

July 2013 3 replicate flights (C1, IM, C2)

October 2013 3 replicate flights (C1, IM, C2)

May 2014 3 replicate flights (C1, IM) 2 replicate flights (C2)

Boat surveys

Darwin Harbour and surrounding waters

June 2012

Transects and Point-Sampling

1 replicate (15 point sampling sites and transects)

August 2012

Transects and Point-Sampling

2 replicates (20 point sampling sites and transects)

October 2012

Point-Sampling2 replicates (20 point sampling sites)

-- -- -- --

Land surveys -- -- -- --

May 2013 2 replicates - Channel Island Bridge and Cullen Bay rock wall

July 2013 2 replicates - Channel Island Bridge and Cullen Bay rock wall

October 2013 2 replicates - Channel Island Bridge and Cullen Bay rock wall

May 2014 2 replicates - Channel Island Bridge and Cullen Bay rock wall

Turtle satellite and flipper tagging

Channel Island Bridge

-- --

October and November 2012 2 tagging fieldwork events

-- --

November and December 2013 2 tagging fieldwork events

--

Casuarina Beach -- --

October 2012

1 satellite tagging fieldwork event

-- -- -- --

Update on rehabilitated turtles

-- 2 turtles^ 3 turtles^ 4 turtles^ 1 turtle^ 1 turtle^ 2 turtles*

^ Turtles in rehabilitation released during this period since the end of the previous survey. * One turtle that was suitable for tagging.



2.2 Field Sampling Locations

2.2.1 Aerial Surveys

Aerial surveys were used to collect data over a broad spatial scale within three geographical regions (or blocks) (Figure 2-1):

> ‘Block 1’ Bynoe Harbour (Control location 1 – C1);

> ‘Block 2’ encompassing Darwin Harbour/Hope Inlet to Gunn Point (Impact location – IM); and

> ‘Block 3’ located to the east of Darwin Harbour, from Gunn Point, around the Vernon Islands and across to Melville Island (Control location 2 – C2).

2.2.2 Land Surveys

In order to assess finer-scale aspects of the ecology of turtle and dugong populations, such as behaviour and movement of individuals in relation to frequently utilised habitats or ‘hotspots’ within Darwin Harbour, land surveys were also undertaken during D5 (May 2014) from two locations around Darwin Harbour − Channel Island Bridge and Cullen Bay rock wall (Figure 2-2).

2.2.3 Turtle Tagging

Tagging was initially attempted on nesting female flatback turtles at Casuarina Beach in September 2012 and targeting juvenile turtles near Channel Island Bridge in November 2012. Further tagging attempts to assess patterns of movement and habitat utilisation around Darwin Harbour were undertaken in November 2013 and December 2013. Turtles targeted for tagging were captured in the northern channel adjacent to Channel Island (Figure 2-2, refer to Section 2.3.4 for more details on capture and tagging methodology).

Within any coastal region, there is often the risk of strandings of megafauna that may have resulted from predatory attack, vessel strike, entanglement or, most often, fatality due to unknown injuries. Around Darwin, turtles are occasionally found stranded. Many of these turtles are rehabilitated and subsequently released near the location of capture. During the TDMP, any turtles bought in by various interest groups for rehabilitation by appropriate veterinary clinics, then assessed for possible inclusion in the tagging component. Results are summarised in Section 4.4.4.



Aerial survey blocks and sub-divisions encompassing Bynoe Harbour (C1), Darwin Harbour/Hope Inlet region (IM) and Vernon Islands (C2) Figure 2-1



Land survey sites in Darwin Harbour during D5 (May 2014):Cullen Bay rock wall (left); and Channel Island Bridge (right), also showing the Figure 2-2

turtle tagging site



2.3 Field Methods The field protocol utilised throughout the TDMP follows the methodology outlined in the NEMP (Rev. 4) (Cardno 2013a).

2.3.1 Monitoring Permits

The TDMP was undertaken under an Animal Welfare Licence (No. 041, Animal Welfare Act Section 33 (2)) and Permit to Interfere with Protected Wildlife (Permit No. 44020, Territory Parks and Wildlife Conservation Act 2006). Animal Ethics Approval (turtle tagging) was obtained in October 2012 (Animal Welfare Act, Section 30, and Macquarie University AEC Reference No. 2012/036-2). Department of Land Resource Management (DLRM) and Fisheries S17/3282 special permits were also obtained.


During D5, aerial surveys were undertaken from 9 May 2014 to 25 May 2014 in a Dornier 220 (a high winged, twin prop, turbo engine aircraft), flown by two pilots at a speed of approximately 110 knots and at an altitude of 500 feet (152 m). Three replicate flights were completed in each of the three main survey blocks (C1, IM and C2; Figure 2-1). Each survey followed a traditional strip transect survey design technique, as described by Marsh and Sinclair (1989). Each strip transect width was 200 m on each side of the aircraft, on which a tandem team of two observers operated (i.e. four observers in total). Each observer’s window was demarcated into four horizontal transect zones, which corresponded with areas (or sub-strips) of water within the strip transects (Low: 0 m to 50 m from the ground position of the aircraft; Medium: 50 m to 100 m; High: 100 m to 150 m; and Very High: 150 m to 200 m; see Figure 2-3). These transect zones were referred to when recording sighting locations over the aircraft audio system. Sightings on the ‘inside’ or the ‘outside’ of these zones, which refers to sightings inside (In) or beyond (Out) the 200 m transect width either side of the plane, were also recorded.

During most aerial surveys undertaken during the TDMP (B1 to B3, D2 and D4), each transect followed an approximate north-east to south-west alignment (Figure 2-1), spaced equally at 2 km intervals, which minimised the chance of sighting the same animal twice, while maximising the aerial coverage (approximately 20%) of the survey block. However, during D3 and D5, the orientation of transects within the C1 and C2 blocks were slightly altered where necessary to accommodate for excessive glare. Each of the three replicate flights flown within the IM block during D3 was flown in a north-east to south-west alignment at 2 km intervals, regardless of the time of day, due to restrictions enforced by Air Traffic Control.

Dugongs, turtles, dolphins and any incidental sightings (e.g. sharks, rays, sea snakes, crocodiles etc.) were recorded in each aerial survey. Environmental and water variables (Beaufort Sea State (BSS), glare and turbidity based on a standardised scale used in aerial surveys (Hodgson et al. 2011)) were also recorded at the start and end of each transect (BSS and glare) or for each sighting (turbidity). It should be noted that dolphins and other incidental sightings are not reported as part of the TDMP. Further details of the aerial survey methods are given in the TDMP Baseline Report (Cardno 2012).



Plane window calibration for aerial surveys (top dotted line = Very High; bottom dotted Figure 2-3line = Low)

2.3.3 Land Surveys

Land surveys during D5 (May 2014) were undertaken from Channel Island Bridge and the rock wall at Cullen Bay. At each site, a maximum of four hours of active observation was undertaken per day over two days, which included eight 30-minute observation periods separated by 15-minute (‘off-effort’) windows. Observation periods were initiated only when the BSS was less than or equal to 3, which maximised the ability to sight marine megafauna. During each 30-minute observation period, observers scanned the water continuously (aided by polarised sunglasses) and assessed any surface disturbance with binoculars to identify the presence of any species of interest. When megafauna were sighted, the following data were recorded on a data sheet:

> Date and time of each sighting (if more than one animal was sighted at any one time, the priority was to gather data for the first animal sighted);

> Animal type: turtle, dugong, dolphin or other incidental sightings (including an identification ranking of certain, probable or uncertain); species identification was also attempted, and then ranked as certain or uncertain;

> Number of individuals (where multiple individuals were involved in a sighting);

> Bearing of sighting from the observer (using a hand-held compass or inbuilt compass in the binoculars);

> Estimated distance from the observer to the sighting; and

> Behavioural activity (e.g. foraging or travelling) or sighting cue (e.g. splash, head or back).

Environmental and water variables (BSS, glare and turbidity based on Hodgson et al. 2011) were recorded at the start and end of each observation period, while the position of each observer was recorded using a hand-held GPS. Average BSS and turbidity, representing the mean of the values recorded by the two observers, was calculated for the start and end of each 30-minute observation period during the first and second replicate surveys. Where possible, confirmed cases of multiple sightings of individuals were recorded; however, this was generally not reliable for turtles or dugongs.

2.3.3.1 Channel Island Bridge

Two observers were concurrently used per survey at Channel Island Bridge (Figure 2-2). One observer was positioned on the northern side of the bridge observing north, while the second observer was located on the southern side of the bridge observing to the south. Each observer was situated in the middle of the bridge (slightly offset to avoid traffic) and observed the approximate width of the channel on their side.



2.3.3.2 Cullen Bay Rock Wall

Two observers were used per survey, placed at the end of the rock wall at Cullen Bay (Figure 2-2), with one observing the east to north quadrant towards Fannie Bay and the other observing the west to north quadrant, which included Cullen Bay.


There were four turtle tagging field events during the TDMP. In September 2012, tagging was initially attempted at Casuarina Beach (16 September 2012 to 28 September 2012 for nesting flatback turtles) and Channel Island Bridge (16 September 2012 to 21 September 2012 for green or hawksbill turtles), with no successful satellite tags deployed.

Tagging was then attempted in November 2012 (13 November 2012 to 18 November 2012), and again in November 2013 and December 2013 (4 November 2013 to 7 November 2013 and 3 December 2013 to 6 December 2013), using a large-mesh monofilament net deployed from a small boat. Tagging events at Channel Island targeted periods around extreme spring low tides when the turtles are forced into the narrow channels and hence can be netted most effectively. Nets were set approximately three hours before and after low tide each day over a four to five day period.

2.3.4.1 Netting Turtles

Turtles were captured for tagging using a 100 m, 10 inch monofilament mesh net set across the shallow northern channel at Channel Island from a 5 m vessel (MV Daly River, Work Boats Northern Australia). This area is near a mixed epibenthic reef community at Channel Island where turtles are known to occur frequently (Whiting 2001). The reef is predominantly submerged during the daytime except during extreme low tide events which occur twice annually (around February and November). During the bottom of the run out tides in these low tide events, turtles are forced off the reef platform and into the deeper water of the channel. The movement of turtles between the reef platform and the channel during these low tide periods provides an opportunity to capture turtles. During other tidal states, the distribution of turtles is too dispersed and the tidal induced currents are too strong for capture.

Turtles caught up in the net were indicated by atypical movement patterns of the surface floats positioned along the length of the net, approximately 2 m apart. Entangled turtles were removed from the net immediately using a scoop net or by hand and placed in a hessian sack on-board the vessel.

2.3.4.2 Attaching Tags

Each turtle of sufficient weight suitable for tagging (i.e. when the weight of the tag used did not exceed 3% of the turtle’s body weight) was fitted with a Wildlife Computer MK10 satellite transmitter (Figure 2-4), attached to the dorsal surface of the shell (carapace) using a standard satellite attachment methodology outlined in the Turtle Satellite Tagging Work Instruction.

Tagged sub-adult green turtle, ‘Pepin’, caught November 2013 (see Section 4.4.1) Figure 2-4



2.4 Assumptions and Constraints


Aerial surveys are widely used to estimate the distribution and relative abundance of marine megafauna over relatively large spatial and temporal scales. Changes in densities over time can also be estimated and are useful indices of changes in abundance, as potential biases become irrelevant as long as biases are held constant by rigid standardised techniques. The approach does, however, assume that the ability to sight dugongs and turtles is largely dependent on water turbidity and sea state, hence the biases.

The average wind strength during D5 was BSS = 2.4 (range from 0 to 4), which was higher than during Baseline Phase surveys (average of BSS = 2; Cardno 2012), and similar to previous Dredging Phase surveys (average of BSS = 2.3, Cardno 2013b-d, 2014). Despite the moderate wind throughout these surveys, excessive wind (BSS ~5) occurred during some D5 flight periods. This was most evident in C2 due to the exposure to the prevailing wind, resulting in flights having to be flown in late afternoon and increasing the effect of glare due to the angle of the sun. Therefore, to minimise the effect of excessive wind and glare at this location, which could have potentially impeded the observability of animals, the orientation of transects was changed from a north-east/south-west orientation to a more north-west/south-east orientation. Furthermore, two sub-blocks in C2 were flown during the third replicate flight, but due to excessive wind (BSS ~ 5) for most of the survey area, these data were not included in analysis. As both B1 and D2 also had only two replicate flights completed in the C2 block, the reduced replication does not affect comparisons between these temporally comparable surveys (May 2012 and May 2013). Nonetheless, caution should be taken when interpreting comparisons between those three surveys and other Baseline and Dredging Phase surveys (three replicate flights) due to the difference in the number of replicate flights.

2.4.2 Land Surveys

During land surveys neither the species of turtle nor any identifying characteristics (e.g. scars, deformities) of most individual turtles or dugongs were able to be recognised from the viewing location so it is likely that some animals were counted more than once. Therefore, during sampling events it is likely that the total recorded number of sightings for a given site is higher than the actual number of individuals present. Furthermore, by having a relatively large area to observe (particularly at Channel Island Bridge), there was also the potential that some sightings were missed as the whole area cannot be scanned simultaneously.


Using a net was determined to be the most appropriate means of turtle capture for the monitoring program over rodeo methods due to the conditions present in Darwin Harbour. While rodeo capture methods, which involve diving into the water and physically catching the turtle, may have enabled more turtles to be caught, the bathymetry, lack of in-water visibility, presence of crocodiles and box jelly fish and other safety issues associated with this method in Darwin Harbour made it unsuitable for this monitoring program.

Despite modifications that aimed to reduce the visibility of the net to turtles, a small proportion of turtles were able to detect the net and subsequently avoid capture. Some turtles were also able to release themselves from the net following entanglement. These factors contributed to the small number of turtles caught during the TDMP.



2.5 Data Analysis


2.5.1.1 Distribution and Habitat Use

For each turtle or dugong sighting, the corrected instantaneous water depth was determined by estimating the vertical difference between the tidal water level and the underwater bed strata depth. This involved combining the tidal height at the time and position of each sighting (relative to mean sea level (MSL)) and the bed strata depth at that position (also relative to MSL). The tidal level at the time of each sighting was obtained from predicted tides for the Darwin area which is provided by the National Tidal Centre (NTC). Spatial variation among the survey blocks in the heights and timing associated with the tidal cycle was assumed to be negligible, although it is acknowledged that variations do exist.

The bed strata depths were determined using two different bathymetric data sets, with the primary source being the Australian Hydrographical Service nautical charts (Australian Hydrographic Service 2003, 2007, 2009a, b). For sightings outside the boundaries of these charts, depths were sourced from the Geoscience Australia Bathymetry and Topography Grid (Whiteway 2009), which has a 250 m grid cell resolution.

Corrected instantaneous water depths were rounded to one decimal place and sightings were assigned to one of five depth categories, defined as:

> 0 m to 5 m (0 m to 5.9 m)

> 6 m to 10 m (6.0 m to 10.9 m)

> 11 m to 20 m (11.0 m to 20.9 m)

> 21 m to 30 m (21.0 m to 30.9 m)

> ≥ 31 m (≥ 31.0 m)

Benthic habitat was determined for each sighting from habitat maps of the Darwin region. These maps were developed primarily from data collected for the draft Environmental Impact Statement (EIS) for the Project (INPEX 2011), in conjunction with other subtidal and intertidal surveys of hard coral, macroalgae, filter feeder and seagrass communities on the reef and sediment substrata in the Darwin region. The GPS locations for each turtle or dugong sighting were able to be overlaid with this spatial data to determine the benthic habitat present at each location. Habitat types were categorised as:

> Sand;

> Reef (includes reef mixed communities, macroalgae and filter feeders);

> Seagrass;

> Mangrove;

> Gravel;

> Mud;

> Rock; and

> Unsurveyed (any benthic habitat that had not yet been defined).

2.5.1.2 Dugong and Turtle Population Estimates and Densities

Population estimates of dugongs and turtles for each survey block (C1, IM and C2) were calculated separately using two different methods, as described by Marsh and Sinclair (1989) and Pollock et al. (2006). The Marsh and Sinclair (1989) method uses estimates of availability and perception biases averaged for each aerial survey, and therefore only corrects for differences in sighting conditions between surveys; by contrast, the Pollock et al. (2006) method accounts for differences in sighting conditions for each sighting.

Population estimates were based on the estimated number of animals (turtles or dugongs) for each tandem team per transect, which were corrected by the appropriate correction factors (perception and availability bias), mean group size (i.e. mean number of animals in sighted groups) and density (number of sightings per km2). Both methods attempt to correct for availability bias (animals not available to observers because of



water turbidity) by applying availability correction factors (ACFs) and perception bias (animals visible in each transect but missed by observers) by applying perception correction factors (PCFs). However, spatial heterogeneity in sighting conditions among observations was only addressed by the ACF associated with the Pollock et al. (2006) method, while the Marsh and Sinclair (1989) ACF method averages conditions within each replicate flight for each spatial block (or sub-block) and only corrects for differences in availability bias between spatial or temporal partitions (i.e. blocks or surveys).

Where possible, dugong and turtle population estimates were calculated for each block (n = 3) using the Marsh and Sinclair (1989) and Pollock et al. (2006) methods. Due to limited dugong sightings throughout the TDMP, population estimates for sub-blocks (n = 14) were calculated only for turtles. For the turtle population estimate calculations, blocks were further partitioned into sub-blocks (C1 – four sub-blocks; IM – six sub-blocks; C2 – four sub-blocks), each of which comprised areas of similar bottom type and bathymetry, such as intertidal, inshore or offshore. While population estimates can be calculated based on any number of sightings (< 5), the variances associated with calculations are large, therefore reducing the reliability. As such, only replicate flights in which five or more sightings were recorded were used for population estimations, which has been consistent protocol across all flights throughout all of the Baseline and Dredging Phase aerial surveys.

For calculation of PCF values using the Marsh and Sinclair (1989) method and for modelling of perception bias in MARK (a program that provides parameters used to estimate population size for the Pollock et al. (2006) method), data were pooled by block instead of by replicate flight. The latter was undertaken for surveys completed prior to D3 (July 2013). For D3, D4 and D5, aerial transect data were pooled within blocks for those calculations as, unlike surveys prior to D3, the observer team was consistent across all replicate flights and the order of transects flown was determined haphazardly and based on environmental conditions, as opposed to a strict, structured order. As with previous analyses conducted within other aerial surveys, group size and corresponding Coefficient of Variation (CV) values were determined for each replicate flight. Values of CV are used to compare the standard deviations between populations with different means and provide measures of variation that are independent of the measurement units.

Density estimates for dugongs and turtles were then calculated by dividing the derived population estimates or raw sightings data by the total transect area sampled over water within each of the three blocks, 14 sub-blocks and 43 individual 6 km x 6 km grid cells that are overlayed within the IM block only.

2.5.1.3 Statistical Analysis

Population density estimates (number per km2) for dugongs and turtles were derived, where appropriate, for replicate flights undertaken in blocks and sub-blocks using three methods:

> Marsh and Sinclair (1989) population estimates;

> Pollock et al. (2006) population estimates; and

> Raw sightings data.

Datasets derived via these three methods were analysed separately. Density estimates derived from Marsh and Sinclair (1989) and Pollock et al. (2006) population estimates were calculated only for replicate flights (within each survey block) with five or more sightings per flight.

Spatial and temporal differences in dugong and turtle densities were then analysed via permutational univariate analyses of variance (PERMANOVA, Anderson 2001), using Euclidean dissimilarity resemblance matrices with unrestricted data permutation methodology.

The four factors used in the analysis of each density dataset were:

> Phase (fixed, orthogonal): 2 levels (Baseline and Dredging Phase, equivalent to the ‘Before-After-Control-Impact’ comparison in BACI);

> Survey (random, nested within Phase): B1, B2 and B3 within Baseline Phase; and D2, D3, D4 and D5 within Dredging Phase;

> Treatment (fixed, orthogonal): 2 levels (Impact and Control); and

> Block (random, nested within Treatment): IM within Impact treatment; and C1 and C2 within Control treatment.



Pooling of lower-level terms with the residual term was undertaken only if the p-value of the term to be pooled was ≥ 0.25. Results for both the pooled and the un-pooled versions were presented where applicable. Where a term (factor or interaction) was significant at p ≤ 0.05, pair-wise comparisons were used in post-hoc analyses to identify which levels of factors or interaction strata were significantly different. Blocks for which fewer than two replicate flights were available for analysis (i.e. due to < 5 sightings in two or more of the three replicate flights) were not included in analyses.

2.5.2 Land Surveys

Variability in the land surveys compromised the potential for formal analyses to detect any spatial differences and/or temporal changes in abundance of dugongs and turtles. Factors affecting variability included observing conditions (e.g. sea state, glare), variability in sea state and temporal changes in the distribution and movements of the animals themselves. Land-based data have, therefore, been presented in a tabular format with spatial representation of sightings in the form of GIS mapping.


Data on the location, length and duration of dives by satellite tagged turtles were downloaded weekly from ARGOS Worldwide Tracking and Environmental Monitoring Systems (www.argos.com) or Seaturtle.org, which provided both ARGOS and Fastloc GPS positions and histogram dive data. ARGOS location points are based on seven levels of accuracy, denoted by a location class (LC) of numerical or alpha value. LC-3 is most accurate with a given error of < 150 m; LC-2 has an error of 150 m to 350 m; LC-1 has an error margin of 350 m to 1000 m; and LC-0 has an error > 1000 m. Alpha LC values (A, B and Z) and LC-0 are the most commonly received, although these locations do not include error estimates.

Development of Fastloc GPS technology (hardware developed by Wildtrack Telemetry Systems Ltd, United Kingdom) has allowed simultaneous collection of GPS and ARGOS locations from tagged marine fauna. Fastloc GPS is able to obtain GPS satellite data in less than 100 ms by capturing satellite signals, identifying the relevant satellites and calculating their pseudo-ranges, before transmitting the data through the ARGOS system. A higher number of satellite signals enable greater accuracy when giving GPS locations, with nine satellites giving very accurate location data, and < 4 often not being able to give a GPS position (these data are discounted for plotted data).

The accuracy of Fastloc GPS locations have been found to be far greater than the ARGOS positions (Costa et al. 2010), and thus these tracks were used for all spatial representation of turtle movements in the form of GIS mapping for the TDMP. Dive duration and depth data have been compiled in Excel and are presented in graph format for comparison among individual turtles.

2.6 Quality Assurance/Quality Control (QA/QC) Species sighting and environmental data from each survey were transcribed and entered into a Microsoft Access database post-flight by each observer and the environmental data collector. As part of the process, 10% of all entries were randomly checked by each tandem team. If any errors were found, a further 10% of records were checked. Any errors were subsequently rechecked and amended in the database before data compilation and analysis. Once all datasets were compiled, the final QA process was undertaken on data in a master database by the Team Leader, where a further 10% of the total number of transects flown were randomly checked.

Land survey data were recorded on datasheets in the field and entered into an Excel spread sheet at the end of each survey by each team. All entries were checked for completeness against field datasheets and any missing cells or information was amended where necessary. As part of the QA process, 10% of records were then checked for errors by random selection. If any errors were found, a further 10% of records were checked, with all errors amended for further data compilation and analyses were completed.



3 Dredging Operations

The dredging program involves a number of dredge vessels including backhoe dredgers (BHDs), cutter suction dredger (CSD) and trailing suction hopper dredgers (TSHDs) operating in different areas depending on water depths, bed material characteristics and the volume of material to be removed.

The EA dredging campaign is divided into five dredging footprint separable portions (SP1 to SP5), which refer to the location and duration of specific dredging activities. The SPs are summarised in Table 3-1 and presented in Figure 3-1.

Dredging for the GEP commenced on 23 October 2013 and EA dredging recommenced for Season Two on 1 November 2013. Dredging for both GEP and EA was completed on 11 June 2014.

Table 3-1 Dredge footprint summary

ID Separable Portion

SP1 Separable Portion 1 − Module Offloading Facility (MOF)

SP2 Separable Portion 2 − Jetty Pocket

SP3 Separable Portion 3 − Berth Area

SP4 Separable Portion 4 − Approach Channel, Berth Approach and Turning Area

SP5 Separable Portion 5 − Walker Shoal



East Arm dredging footprint and GEP routeFigure 3-1



4 Results

Results from the D5 (May 2014) aerial and land surveys, and updated results for the turtle tagging events undertaken in late 2013, are presented in this section. Where appropriate, aerial and land survey data are compared to Baseline Phase (B1 (May 2012), B2 (July 2012) and B3 (October 2012)) and Dredging Phase (D2 (May 2013), D3 (July 2013) and D4 (October 2013) surveys. Detailed results of these individual sampling periods are provided in previous TDMP reports (Cardno 2012, 2013b-d, 2014).

4.1 Aerial Surveys

4.1.1 Survey Effort and Environmental Conditions

The end of dredging survey (D5) was undertaken from 9 May 2014 to 27 May 2014. Three replicate flights were completed in the C1 and IM blocks, and two replicates for the C2 block. A third replicate in C2 was not possible due to persistent excessive winds that made conditions unsuitable for aerial surveying.

During D5, 3,565 km of linear transects were sampled over a cumulative time period of approximately 18 hours. The cumulative total length of the portion of transects flown ‘over water’ during each replicate flight (blocks combined) was 1,349 km, equating to an area of 540 km2 (based on a transect width of 400 m spanning both sides of the plane). The overall area surveyed across all three geographical blocks per replicate flight (variable due to tidal level) was 2,697 km2 (Appendix A). This represented approximately 20% of the total available area within the three blocks.

Conditions during replicate flights were variable (mean BSS = 2.4, range 0 to 4). Due to wind unpredictability, the average BSS varied considerably during the survey, ranging from 1.9 in the first replicate flight on C1, increasing to 3.1 in the final flight in the IM block. Turbidity, based on Hodgson et al. 2011, ranged between 1 and 4, with an average of 3.8. During D5, C1 and IM were flown in a north-east to south-west alignment orientation as per TDMP protocol. However, due to wind conditions it was more suitable to survey C2 in the afternoon to minimise excessive glare (refer to Section 2.4.1) and, as such, this block was flown in a north-west to south-east alignment.

4.1.2 Dugongs

4.1.2.1 Sightings and Distribution

Ninety seven dugongs were sighted during D5 across all three survey blocks, during eight replicate flights (C1: n = 20 dugongs, 3 flights (‘Reps’); IM: n = 39, 3 Reps; C2: n = 38, 2 Reps; Figure 4-1). This was considerably higher than the total number of dugongs sighted during similar temporal periods in the monitoring program in May 2013 (D2, 33 dugongs) and May 2012 (B1, 58 dugongs). This was, however, comparable to the average number of dugongs sighted across all Baseline Phase surveys, with an average of 88 sightings across the three blocks (B1, n = 58, 6 Reps; B2, n = 92, 9 Reps; B3, n = 113, 9 Reps; Appendix B). The total number of dugongs sighted during D5 was higher than the number of dugongs sighted during the other Dredging Phase surveys (D2, n = 33, 8 flights; D3, n = 71, 9 Reps; D4, n = 87, 9 Reps).

Dugongs sighted during D5 were predominantly adults, consistent with all aerial surveys undertaken during the TDMP. Calves have been sighted in each block, with more regularly observed in the IM block over the duration of the TDMP than in either C1 or C2. The highest number of calves was sighted in B2 and D4 where seven calves were observed during each survey, five of which were sighted in the IM block on each occasion (Appendix B). The least number of dugong calves were observed in C1, with three sighted over the duration of the monitoring program, including one calf in each of the B1, D3 and D5 surveys. In C2, there were nine calf sightings overall, with two in B2, D3 and D4 and one in B1. In the IM block, 16 dugong calves were sighted, contributing to over half of the total number seen throughout the TDMP. They have been observed in IM during every survey except D5.

Based on raw sightings data, the mean numbers of dugongs (± SE) sighted within each block during D5 were C1: 6.7 ± 2.3, IM: 13.0 ± 4.6 (n = 3 flights), while in the C2 block the mean number was 19.0 ± 8.0 (n = 2 flights) (Figure 4-2). The mean number of dugongs for C1 and IM during D5 were similar to the



May 2012 Baseline Phase survey (B1), during which 7.0 ± 1.0 and 12.5 ± 1.5 dugongs were sighted in C1 and IM, respectively.

In contrast, the mean number of dugongs sighted in C2 during D5 (19.0 ± 8.0), was approximately twice that for B1 (9.5 ± 1.5). Conversely, the D5 survey had considerably more dugongs sighted overall than for D2, with the mean number of dugongs sighted in D2 calculated to be 2.0 ± 0.0 in C1, 5.3 ± 1.9 in IM and 5.5 ± 2.5 in C2.

Across the Baseline Phase surveys, 263 dugongs were sighted over three survey periods (B1, B2 and B3 combined; mean of 88 dugongs per survey); while 288 dugongs in total were sighted across Dredging Phase surveys (D2, D3, D4 and D5 combined; mean of 72 dugongs per survey). Refer to Table 2-1 for a summary of aerial surveys sampling effort. The mean number of dugongs sighted across the Baseline and Dredging Phases were similar in the C2 block (9.0 ± 2.4 and 9.3 ± 2.4, respectively). In comparison, there was a higher number of dugongs sighted during the Baseline Phase in C1 and IM (C1: 7.0 ± 1.5, IM: 16.6 ± 3), than during the Dredging Phase (C1: 4.8 ± 0.8, IM: 11.8 ± 1.7). The D2 survey had the lowest number of animals across all blocks for all Baseline and Dredging Phase surveys and there has been a considerable increase in sightings from D2 to D5 (Figure 4-2).

During D5, higher concentrations of dugongs were observed around the shallow areas near the islands north of Bynoe Harbour (C1), and the Vernon Islands (C2) (Figure 4-1) compared with previous surveys undertaken at a comparable time of year. Within the IM block, dugong distribution varied considerably over time. Dugongs were sighted in Darwin Harbour Inner and Darwin Outer (sub-divisions IM1 and IM2 to IM6, respectively; Figure 4-1) during all Baseline Phase surveys. In B2, most sightings in the IM block were around Weed Reef, West Arm and near Bladin Point, as well as the shallow regions of Shoal Bay; in B3, most dugong sightings were around Darwin Outer, with aggregations around mapped seagrass near Casuarina Beach (Appendix C).

During the Dredging Phase surveys, dugongs were predominantly sighted in the Darwin Outer region, with only one dugong sighted near Weed Reef and another in the shallow areas in West Arm in D2. During D3 and D4, no dugongs were sighted in Darwin Harbour Inner while during D5, three dugongs were sighted near Weed Reef over two replicate flights (Figure 4-1). During the two surveys undertaken in the month of October (B3 and D4), in the outer areas of the IM block sightings have been more concentrated around Casuarina Beach, where areas of the Halodule genus of seagrass were recorded during these time periods as part of the seagrass monitoring program (GeoOceans 2012, 2013b). However, during the May surveys (B1, D2 and D5) there were few sightings around Casuarina Beach and Fannie Bay, with greater aggregations through Shoal Bay towards Gunn Point (Appendix C-1). Reduced seagrass distributions around Casuarina Beach and Fannie Bay have been observed during seagrass monitoring in the late wet season, likely due to wet season conditions, such as the storm events in January 2014 and February 2014 (Cardno 2014b).



Distribution of dugongs (based on raw sightings) among and within sub-blocks during D5 aerial surveys (three replicate flights) Figure 4-1



Mean counts per replicate (± SE) of dugongs sighted in each block (C1, IM and C2) for all Figure 4-2aerial surveys completed to date (B1 (May 2012) to D5 (May 2014)) N.B. Only two replicate flights were carried out during B1 (across all blocks) and only two replicate flights in the C2 block during D2 and D5

The highest density of dugongs recorded in the IM block during D5 (based on raw sightings within designated 6 km x 6 km grids) was positioned around Shoal Bay between Lee Point and Gunn Point (grid cells 15 (1.11/km2) and 22 (1.25/km2) (Figure 4-3). This spatial pattern is similar to that observed in previous surveys during the same temporal period in 2012 (B1) and 2013 (D2); however, the density in these grids in D5 was higher than for previous surveys. Dugongs were also sighted around Weed Reef (grid cell 31) and off East Point (grid cell 26) within Darwin Harbour Inner during D5.

The change in dugong density over time, from D5 compared with D2 and B1, is presented in Figure 4-4 and Figure 4-5, respectively. The density of dugongs sighted during D5 increased by more than 0.2 dugongs per km2 since D2 in 23% of area, and decreased by approximately 0.2 dugongs per km2 since D2 densities in 9% of IM grid cells. A relatively small change (between -0.2 and 0.2 dugongs per km2) between D5 and D2 was evident in 67% of IM grid cells (Figure 4-4). Dugong densities were zero in D5 and D2 in over half of the IM area (58%), which incorporates both the Darwin Harbour Inner and Darwin Outer regions.

Compared with B1, dugong densities during D5 increased by more than 0.2 dugongs per km2 in 19% of the IM grid cells (Figure 4-5), and decreased by more than 0.2 dugongs per km2 in 14% of IM grid cells. Between D5 and D2, a relatively small change (between -0.2 and 0.2 dugongs per km2) was detected in 67% of IM grid cells. In 56% of IM grid cells, dugong densities were zero in D2 and D5.

When comparing similar temporal periods (B1, D2 and D5), no dugongs were sighted in 42% of IM grid cells. No dugongs have been sighted during any survey in 64% of the IM grid cells within Darwin Harbour Inner, compared with 31% of the IM grid cells within Darwin Outer. Within Darwin Harbour Inner, dugongs have only been sighted around Fannie Bay, Weed Reef and near the openings of Elizabeth River and Blackmore River (grid cells 26, 30, 31, 40, 42; Figure 4-4, Figure 4-5).

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Density of dugong sightings (based on raw counts) per km2 of transect area sampled over water within 6 km x 6 km grids at IM during D5 Figure 4-3

(May 2014)



Relative difference in dugong density (based on raw counts) per km2 of transect area sampled over water within 6 km x 6 km grids in IM Figure 4-4

during D5 (May 2014) compared with D2 (May 2013)



Relative difference in the dugong density (based on raw counts) per km2 of transect area sampled over water within 6 km x 6 km grids at IM Figure 4-5

during D5 (May 2014) compared with B1 (May 2012)



4.1.2.2 Dugong Bathymetric Distribution and Habitat Associations

During D5, the majority of dugongs were sighted in waters less than 11 m in depth (80%), with a maximum depth of 24 m. Of the 97 dugong sightings across all blocks, 50% occurred in waters ≤ 5 m deep, 32% in waters 6 m to 10 m deep, 12% in waters 11 m to 20 m deep and 6% in waters 21 m to 30 m deep. Spatially, the depth distribution of dugongs sighted across all blocks varied considerably during D5, with the majority of dugongs (95%) sighted in C1 in waters less than 5 m and the remainder in 6 m to 10 m water depths. During D5, no sightings were made at depths greater than 10 m in C1, similar to previous surveys undertaken at a similar time of year (B1 and D2) (Figure 4-6).

In the IM block, a pattern of decreasing occurrence with increasing depth was found, which was generally consistent across all previous surveys (B1 to D4). This pattern was more gradual compared with previous surveys (B1 and D2), with proportionally fewer dugongs sighted in the 0 m to 5 m depth category (44%). In IM, there was a comparatively slower decrease in sightings, with 28% of sightings in waters of 6 m to 10 m depth, 15% of sightings in the 11 m to 20 m depth category and 13% in the 21 m to 30 m depth range.

In C2, the highest quantities of dugongs were sighted in the 0 m to 5 m and 6 m to 10 m depth categories (32% and 50%, respectively), whilst only 16% of dugongs were sighted in 11 m to 20 m depths. This differs from the trends observed in either the B1 and D2 surveys, where the majority of sightings occurred in waters between 11 m and 20 m (B1: 53%, D2: 50%). This shows a substantial increase in the number of dugong sightings made in waters between 6 m and 10 m depth, and a reduction in those between 11 m and 20 m depth during D5, in comparison to the previous surveys undertaken at a similar time of year (B1 and D2).

During D5, 44% of dugong sightings occurred over gravel, 36% over sand habitat and 18% over reef, with only approximately 1% occurring within seagrass and mud habitat types. There were no dugong sightings made over unsurveyed substrata during D5, while 0% and 6% of sightings were over unsurveyed substrata during surveys B1 and D2.

Patterns in the spatial distribution of dugong sightings within C1 and IM across different benthic habitat types were generally similar in D5 compared with D2, whilst C2 showed more variability between sightings in specific habitat types between the surveys (Figure 4-7). In C1, dugong sightings occurred over either sand (35%) or gravel (65%) habitat types, consistent with sightings during the B1 and D2 surveys, whereas in IM, the majority of dugongs (67%) were sighted over sand substrata. Relatively lower proportions of dugong sightings occurred over reef, seagrass, and gravel and mud habitat types during this survey period, similar to trends observed in the previous surveys at the same temporal period (B1 and D2). In C2, 55% and 39% of dugong sightings were over gravel and reef respectively, with the remaining sightings occurring over sand. In comparison to D2, proportionally fewer sightings occurred over sand and reef, whilst a greater number were over gravel habitat.



Proportion of dugong sightings within different depth ranges (m) in: a) C1; b) IM; and c) Figure 4-6C2 during B1 (May 2012), D2 (May 2013) and D5 (May 2014)

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Proportion of dugong sightings with respect to benthic habitat types at: a) C1; b) IM; Figure 4-7and c) C2 during B1 (May 2012), D2 (May 2013) and D5 (May 2014)

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4.1.2.3 Estimates of Dugong Population Size – Whole Blocks

Mean group sizes of dugongs sighted in blocks C1, IM and C2 during the D5 survey and the associated correction factors (PCF and ACF) used for estimating the size of populations (using the Marsh and Sinclair (1989) method) are presented in Table 4-1. Due to the small number of dugong sightings, PCFs and ACFs were calculated using all sightings combined across blocks, while group sizes and CV were calculated for each replicate flight. The estimates were based on all dugong sightings, including those in the ‘inside’ and ‘outside’ zones (refer to Section 2.3.2).

Table 4-1 Details of group size estimates and correction factors used in dugong population estimates for D5 (May 2014) aerial surveys N.B. these parameters were used in the Marsh and Sinclair (1989) population estimate methods only: PCF – Perception Correction Factor; ACF – Availability Correction Factor; CV – Coefficient of Variation

Survey Block Replicate Mean group size (CV) PCF (CV) ACF (CV)

Total mean group size

(CV)

Starboard Port

D5

C1

1 1.29 (0.13)

1.18 (0.05) 1.58 (0.14) 2.53 (0.15) 1.32 (0.05)

2 1.29 (0.13)

3 1.00 (0.00)

IM

1 1.40 (0.09)

2 1.00 (0.00)

3 1.30 (0.16)

C2

1 1.38 (0.13)

2 1.69 (0.14)

3^ -- ^ Two replicate flights undertaken in C2.

Inter- and intra-survey temporal variation was evident throughout the TDMP. During D5, five or more dugongs were sighted in seven of the eight replicate flights (IM: Reps 1, 2 and 3; C1: Reps 1 and 2; C2: Reps 1 and 2) (Table 4-2). In C1, dugong populations were only estimated for the first and second replicate flights due to limited sightings (i.e. < 5) during the third replicate. Based on this, the mean population estimate (across replicate flights) for dugongs in the C1 block during D5 (± SE) was calculated to be 173 ± 54 dugongs using the Marsh and Sinclair (1989) method, which was comparable to the mean population estimate calculated for B1 (176 ± 84) (Table 4-3). No estimates were possible for the D2 survey due to minimal dugong sightings. Compared with earlier aerial surveys undertaken at other times of year, the mean population estimate calculated for C1 during D5 was lower than mean estimates for D4 (181 ± 84) and B2 (287 ± 65), but higher than those for B3 (157 ± 112) and D3 (134 ± 58) (Figure 4-8a).

Compared with the Marsh and Sinclair (1989) method, mean population estimates for D5 calculated using the Pollock et al. (2006) method were lower for all survey blocks (C1: 94 ± 50; IM: 207 ± 96; C2: 274 ± 130; Table 4-3), as has been the case in previous surveys (Figure 4-8). Whilst the D5 values from the different methods of estimation were similar for IM and C2, they varied greatly in the C1 block (Table 4-3).

In the IM block, dugong population estimates calculated for each of the three replicate flights during D5 using the Marsh and Sinclair (1989) method ranged from 120 ± 52 (Rep 2) to 349 ± 103 (Rep 1), with a mean population estimate of 226 ± 118 dugongs. Compared with temporally comparable periods, the mean D5 dugong population estimate was similar to that for B1 (243 ± 61), but substantially greater than for D2 (99 ± 48). However, those three mean population estimates were the lowest across all surveys, with D5 lower than mean population estimates for B2 (411 ± 127), B3 (401 ± 167), D3 (315 ± 170) and D4 (382 ± 154) but within the error for each survey (Figure 4-8a).

Using the Pollock et al. (2006) method, population estimates for D5 ranged from 126 ± 48 (Rep 2) to 313 ± 79 (Rep 1). Population estimates for the C2 block during D5 were calculated for two replicate flights only, and



ranged from 187 ± 105 (Rep 1) to 455 ± 208 (Rep 2), giving an overall mean population estimate of 321 ± 172 using the Marsh and Sinclair (1989) method. This was substantially higher than previous surveys during similar temporal periods (B1: 188 ± 85; D2: 93 ± 45); however, the estimate calculated for D5 was also comparable to the estimate from B2 (325 ± 78) (Figure 4-8). Using the Pollock et al. (2006) method, population estimates were calculated to be 159 ± 62 (Rep 1) and 389 ± 141 (Rep 2), giving a mean estimate of 274 ± 130 (Table 4-3).

Overall, dugong population estimates obtained for all blocks (C1, IM and C2) during D5 using the Marsh and Sinclair (1989) method were higher than corresponding estimates for the Baseline Phase in the case of C2, but lower in the cases of C1 and IM (Table 4-3). However, when comparing between phases, mean population estimates (averaged across surveys) were lower in the Dredging Phase for the C1 block (141 ± 76) and IM block (287 ± 176), but higher in C2 (251 ± 172), compared with the Baseline Phase (C1: 190 ± 103; IM: 359 ± 154; C2: 227 ± 109) (Table 4-3b). The same trend was evident when using the Pollock et al. (2006) method; however, the differences between Baseline and Dredging Phases were far greater for some blocks (C1 and IM) compared with the Marsh and Sinclair (1989) estimates (Table 4-3b). However, in both estimation methods, there was considerable imprecision associated with most of these estimates as evident in the large overlapping SE values (Figure 4-8) suggesting that, while means varied, fluctuating values were still within the large margins of error. Furthermore, when comparing across surveys, due to low sighting numbers (i.e. < 5 dugongs), population estimates may be based on only one replicate (see Table 4-3), potentially introducing inaccuracy due to low replication.

Table 4-2 Sighting histories for dugong groups sighted during D5 aerial surveys by individual observers for all flights combined*

Block Rep Number of dugong groups seen by:

# dugongs sighted / replicate

Total # dugong groups sighted

% dugong groups sighted by both observers

PF PR PB SF SR SB Port Starboard

C1

1 3 1 1 2 0 1 9 8 20% 33%

2 2 2 1 1 0 2 9 8 20% 67%

3 0 1 0 0 0 1 2 2 0% 100%

IM

1 4 2 1 2 2 4 21 15 14% 50%

2 2 0 2 1 0 0 5 5 50% 0%

3 0 2 0 1 3 4 13 10 0% 50%

C2

1 1 1 1 3 1 1 11 8 33% 20%

2 4 3 4 6 0 2 27 19 36% 25%

3 - - - - - - - - - -

Total 18 16 11 17 8 18 116 88 26% 41%

Port front (PF); port rear (PR); port both (PB); starboard front (SF); starboard rear (SR) and starboard both (SB). * All dugong sightings combined (given in Total) were used for estimates for PCF and MARK analysis in the D5 survey.



Table 4-3 Comparison of dugong population estimates (± SE) and number of replicates where estimates were able to be derived (n) for: a) each block during B1, D2 and D5; and b) across Baseline and Dredging Phases, based on Marsh and Sinclair (1989) and Pollock et al. (2006)

a) B1 D2 D5

Estimation Method Block Estimate ± SE n Estimate ± SE n Estimate ± SE n

Marsh and Sinclair C1 176 84 2 - - 0 173 54 2

IM 243 61 2 99 48 1 226 118 3

C2 188 85 2 93 45 1 321 172 2

Pollock et al. C1 111 75 2 - - 0 94 50 2

IM 157 81 2 90 37 1 207 96 3

C2 114 65 2 67 26 1 274 130 3

b) Baseline Phase Dredging Phase

Estimation Method Block Estimate ± SE n Estimate ± SE n

Marsh and Sinclair C1 190 103 5 141 76 5

IM 359 154 7 287 176 10

C2 227 109 5 251 172 5

Pollock et al. C1 167 168 5 77 53 5

IM 231 138 7 174 79 10

C2 148 105 5 211 126 5



Mean population estimates for dugongs in each block across all surveys (B1 to D5), Figure 4-8

based on: a) Marsh and Sinclair (1989) method; b) Pollock et al. (2006) method; and c) raw sightings data

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4.1.2.4 Dugong Densities – Whole Block

As with the population estimates (Section 4.1.2.3), the density of dugongs per km2 was calculated for Reps 1 and 2 for the C1 block, Reps 1 and 2 for C2, and for each of the three replicate flights in IM during D5. The estimated mean density (± SE) of dugongs in C1 was 0.25 ± 0.04 per km2 based on the Marsh and Sinclair (1989) population estimate method and 0.14 ± 0.01 per km2 based on Pollock et al. (2006) (Figure 4-9). In the IM block, the estimated mean density of dugongs was calculated to be 0.22 ± 0.03 per km2 based on Marsh and Sinclair (1989) and 0.20 ± 0.02 per km2 based on Pollock et al. (2006), whereas in the C2 block densities were 0.33 ± 0.08 dugong per km2 and 0.28 ± 0.06 dugongs per km2 based on the two methods, respectively.

Based on raw sightings, the mean density of dugongs was 0.05 ± 0.02 per km2 for the C1 block, 0.06 ± 0.02 per km2 in IM, and was considerably higher in the C2 block (0.1 ± 0.04 dugongs per km2). The density of dugongs per km2 based on Marsh and Sinclair (1989) and Pollock et al. (2006) estimation methods and raw counts for each replicate flight and survey period within each of the three blocks are presented in Appendix E.

Based on the Marsh and Sinclair (1989) method, the estimated mean population density has shown considerable temporal variation across the survey area. Across all blocks, densities of dugongs were higher in D5 than during seasonably comparable B1 (C1: 0.22 ± 0.04; C2: 0.18 ± 0.03; IM: 0.20 ± 0.03) and D2 (C2: 0.09 ± 0.04; IM: 0.09 ± 0.04). Due to limited sightings in C1 during D2, no estimates were calculated. Across all blocks, there was a noticeable decrease in densities from B3 to D2, with D2 having notably lower dugong densities compared with all other Baseline and Dredging Phase surveys (Figure 4-9).

The highest densities of dugongs throughout the monitoring area were sighted in the IM block during October 2012 (B3: 0.37 ± 0.08) and October 2013 (D4: 0.37 ± 0.05), with a decrease in the IM block during the May 2014 survey (D5: 0.22 ± 0.03). In contrast, in the C2 block, the highest densities of dugongs over both Baseline and Dredging Phases occurred during the May 2014 survey (D5: 0.33 ± 0.08). These patterns were similar for density estimates based on raw sightings. In contrast, estimated mean population densities based on the Pollock et al. (2006) method showed lower temporal variability at all blocks compared with the Marsh and Sinclair (1989) method.



Mean dugong density per km2 (± SE) in each block during the TDMP across all surveys Figure 4-9(B1 to D5), based on: a) Marsh and Sinclair (1989) method; b) Pollock et al. (2006) method; and c) raw sightings

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Significant differences in dugong density estimates derived using the Marsh and Sinclair (1989) method were detected between Surveys within each Phase (all blocks combined, p < 0.05), while no other terms in the analysis were significant (Table 4-4a, Figure 4-10). Pairwise comparisons did not indicate that there were significant differences between any of the surveys despite estimated dugong density being lower in D2 (0.1 ± 0.0 per km2) compared with all the other surveys. It is worth noting that no estimates were calculated for C1 and only one replicate flight was possible for each of C2 and IM blocks during D2 due to low sightings of dugongs.

Analysis of dugong density estimates derived using the Pollock et al. (2006) method (Table 4-4b) and from raw sightings (Table 4-4c) found no significant Phase x Treatment interaction, indicating that mean density did not significantly differ between Impact and Control Treatments during either Phase, or between Baseline and Dredging Phases for either Treatment. There were also no other significant interactions or main effects involving any of the factors in the analyses. These two analyses indicated that, based on these two methodologies, the density of dugongs has not significantly differed through time or among blocks for the duration of the TDMP.

Dugong population density, averaged over all blocks, using the Marsh and Sinclair (1989) Figure 4-10method

4.1.2.5 Dugong Sub-block Population Estimates and Densities

Sub-block estimates and densities were not calculated for D5 aerial surveys as there were too few sightings to compare across sub-blocks and, as such, it would not provide more accurate estimates of population size or reduce the variance.

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Table 4-4 Results of univariate PERMANOVA tests for differences in the density of dugongs per km2 based on: a) the Marsh and Sinclair (1989) method; b) the Pollock et al. (2006) method; and c) raw sightings between two Phases (Baseline and Dredging), including Phase (B1, B2 and B3 within Baseline Phase; and D2, D3, D4 and D5 within Dredging Phase), two Treatments (Control and Impact) and three Blocks (C1 and C2 within Control; and IM within Impact) ( ) Terms pooled with the Residual/Pooled term in the final analysis; ^ No. permutations < 100 so Monte Carlo calculated p-value presented; significant p-values (p ≤ 0.05) in bold

Source of Variation (a) Marsh and Sinclair (1989) (b) Pollock et al. (2006) (c) Raw sightings

df MS Pseu-F p-(perm) df MS Pseu-F p-(perm) df MS Pseu-F p-(perm)

Phase 1 0.0114 0.50 0.7337 1 0.0330 0.61 0.6802 1 0.00278 1.27 0.4147

Treatment 1 0.0091 1.53 0.3687 1 0.0010 1.01 0.4967 1 0.00561 5.08 0.0626

Survey(Phase) 5 0.0233 16.41 0.0210 5 0.0223 2.73 0.3113 5 0.00192 2.51 0.1820

Location(Treatment) 1 0.0007 0.42 0.5581 1 0.0002 0.03 0.8943 1 0.00022 0.29 0.6243

Phase x Treatment 1 0.0002 0.21 0.9072 1 0.0055 0.26 0.9056 1 0.00047 0.64 0.6637

Phase x Location(Treatment) 1 0.0026 1.59 0.3038 1 0.0352 4.71 0.0980 1 0.00088 1.16 0.3340

Treatment x Survey(Phase) 5 0.0063 5.06 0.1040 5 0.0115 1.45 0.4564 5 0.00105 1.39 0.3729

Survey(Phase) x Location(Treatment) 3 0.0014 0.11 0.9587 3 0.0075 1.22 0.3225 5 0.00075 0.75 0.5895

Residual 16 0.0126 18 0.0061 37 0.00100

Total 34 36 57

Pairwise Comparisons Baseline: B2 = B3 = B1

(ranked from largest to smallest) Dredging: D4 = D3 = D5 = D2



4.1.3 Turtles

4.1.3.1 Sightings and Distribution

Eight hundred and twenty seven turtles were sighted during the D5 aerial survey across all three survey blocks (C1: 334, 3 Reps; IM: 192, 3 Reps; C2: 301, 2 Reps). Most sightings were of individual turtles, while groups of two or more turtles were recorded sporadically (Appendix F). The total number of turtles sighted during D5 was considerably higher than during pervious aerial surveys during the same temporal period in 2012 (B1: 334 turtles, 6 Reps) and in 2013 (D2: 627 turtles, 8 Reps), and the second highest overall across all Baseline and Dredging Phase surveys (B3 had the highest count, with 984 turtles, 9 Reps). Regardless of this considerable variation, the mean number of turtles sighted per survey (replicate flights and blocks combined) was similar between Baseline and Dredging Phases, with a mean of 634 turtles sighted per Baseline Phase survey and 699 turtle sightings per Dredging Phase survey (refer to Table 2-1 for a summary of sampling effort across surveys).

Turtle sightings occurred within each of the three survey blocks, consistent with previous Baseline and Dredging Phase surveys. However, during D5 there were notably higher concentrations in shallow waters around the islands to the northwest of Bynoe Harbour, around Casuarina Beach and near Gunn Point in the IM block, and near the Vernon Islands in C2 (Figure 4-11). The temporal variation in turtle distribution sighted within the IM block during D5 compared to during B1 and D2 is shown in Appendix F, and is overlaid with concurrent mapped seagrass habitats from the same period (GeoOceans 2012, 2013a, 2014; Appendix C). Overall, although turtle sightings have generally been concentrated in shallow areas, sightings have shown a high degree of spatial and temporal variability.

During D5, the mean number of turtle sightings within the IM survey block (64.0 ± 17.3, n = 3 Reps) was similar to both the B1 (66.0 ± 8.5, n = 2 Reps) and D2 (62.7 ± 11.0, n = 3 Reps) surveys that were undertaken at a similar temporal period (Figure 4-12). In contrast, the mean number of turtles observed in the C2 block during D5 (150.5 ± 14.5, n = 2 Reps) was substantially greater than for any of the Baseline or Dredging Phase surveys. Mean turtle sightings per replicate flight in C1 were also greater during D5 (111.3 ± 9.0) than during any of the other Baseline or Dredging Phase surveys. Although the mean number of turtles in the IM block has remained relatively consistent over time, the third lowest mean number of turtles of all surveys was recorded during D5 in the IM block.

During D5, the highest relative densities of turtle sightings per km2 in the IM block during the D5 survey were recorded in Darwin Outer around Gunn Point (grid cells 8 and 16; 3.90 and 7.10 turtles per km2,

respectively), near Lee Point (grid cells 20, 21 and 29; 3.02, 3.33 and 4.14 turtles per km2, respectively), Fannie Bay (grid cell 26; 2.51 turtles per km2) and at the western edge near Cox Peninsular (grid cell 43; 4.53 turtles per km2) (Figure 4-13). Within Darwin Harbour Inner, the highest turtle densities per km2 were observed around East Arm (grid cell 36; 1.57 turtles per km2), Middle Arm (grid cell 39; 1.42 turtles per km2) and west towards Weed Reef (grid cell 31; 1.11 turtles per km2), although these densities were considerably lower than those recorded for the aforementioned Darwin Outer grid cells.

The spatial distribution of areas of high and low turtle density was found to be comparable to previously reported density patterns during the Baseline Phase and Dredging Phase surveys. During D5, turtle density increased by more than 0.2 turtles per km2 in 37% of IM grid cells since B1, and decreased by more than 0.2 turtles per km2 in 35% of IM grid cells. A relatively small change in turtle densities (between -0.2 and 0.2 turtles per km2) from the B1 survey to D5 was observed in 28% of the IM grid cells (Figure 4-14). When comparing D5 to D2, the density of turtles per km2 in the IM block increased by more than 0.2 turtles in 33% of the grid cells, and decreased by more than 0.2 turtles per km2 in 42% of grid cells (Figure 4-15), with only a relatively small change (between -0.2 and 0.2 turtles per km2) detected for 26% of IM grid cells. There was an overall decrease in turtle densities of > 0.2 turtles per km2 in 57% of the IM grid cells in Darwin Harbour Inner and 35% of the IM grid cells in Darwin Outer. Across the three surveys (B1, D2 and D5), turtles were not sighted in 7% of grid cells in the IM block (grid cells 27 and 40).



Distribution of turtles (based on raw sightings) during the D5 (May 2014) aerial surveyFigure 4-11



Mean counts per replicate (± SE) of turtles sighted in each block (C1, IM and C2) for all Figure 4-12aerial surveys to date from B1 (May 2012) to D5 (May 2014)

N.B. Two replicate flights were undertaken during B1 (in all blocks), and two replicate flights in the C2 block during D2 and D5

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SE

Survey

C1IMC2



Density of turtle sightings (based on raw counts) per km2 of transect area sampled over water within 6 km x 6 km grids in IM during the D5 Figure 4-13

(May 2014) aerial survey



Relative difference in turtle density (based on raw counts) per km2 of transect area sampled over water within 6 km x 6 km grids in IM Figure 4-14

during the D5 (May 2014) aerial survey compared to B1 (May 2012)



Relative difference in the turtle density (based on raw counts) per km2 of transect area sampled over water within 6 km x 6 km grids in IM Figure 4-15

during the D5 (May 2014) aerial survey compared to D2 (May 2013)



4.1.3.2 Turtle Bathymetric Distribution and Habitat Associations

Turtles were sighted in all water depths during D5, with the vast majority of sightings (96%) occurring in waters less than 20 m in depth. Turtles were sighted to a maximum depth of 52 m, although most were observed in waters ≤ 5 m deep (60%), with a further 16% in waters 6 m to 10 m deep, 20% in waters 11 m to 20 m deep, and 3% in waters 21 m and 30 m deep; only 1% were sighted at water depths greater than 31 m.

The depth distribution of turtle sightings varied between blocks, but was generally consistent across previous surveys undertaken at the same time of the year (B1 and D2) (Figure 4-16). During D5, most turtles around Bynoe Harbour (C1) were sighted in the 0 m to 5 m depth category (84%), with considerably fewer sightings occurring in the depth categories between 6 m and 20 m. This pattern of decreasing occurrence with increasing depth was consistent with sightings occurring in Darwin Harbour/Hope Inlet (IM) areas; however, the decline across depths in IM was more gradual. In IM, 62% of turtles of were sighted in waters between 0 m and 5 m, with a further 21%, 15% and 2% of sightings occurring in the 6 m to 10 m, 11 m to 20 m and 21 m to 30 m depth categories, respectively.

Unlike C1 and IM, the majority of turtle sightings around the Vernon Islands (C2) in D5 occurred in waters between 11 m and 20 m in depth (44%), whilst 31% were in waters less than 5 m and 16% between 6 m to 10 m. In C2, a few turtles (3%) were sighted in deep waters (>30 m), probably associated with the channels between the islands. Overall, these variable patterns of depth distributions for turtle sightings across the blocks were similar to those recorded during previous aerial surveys carried out at the same time of the year (i.e. B1 and D2).

Generally, habitat associations of turtles sighted during D5 were consistent with patterns observed during previous surveys (B1 and D2) across all blocks (Figure 4-17). Overall, turtles were most frequently sighted over gravel and sand (41% and 25%, respectively). Reef and unsurveyed substrata accounted for 16% and 15% of all sightings.

In C1, 74% of sightings occurred over gravel, 25% over sand habitat and less than 1% collectively over mud and rock substrata. In the IM block, turtles were most frequently sighted over sand (52%), with reef and gravel habitat types each accounting for 19% of sightings. There were only a few turtles sighted in association with mangroves, seagrass or mud habitats (0.5%, 7% and 3%, respectively). The majority of turtle sightings in C2 were associated with unsurveyed habitats and reef (40% and 31%, respectively), with proportionally fewer sightings occurring over gravel (19%), sand (8%), mud (3%) and rock (<1%). During D5, comparatively more sightings were associated with reef in C2 than during D2 and B1; however, the trends in habitat associations of turtles were generally consistent across the previous surveys (B1 and D2) for all blocks.



Proportion of turtle sightings observed within different depth ranges (m) in: a) C1; b) Figure 4-16

IM; and c) C2 during the B1 (May 2012), D2 (May 2013) and D5 (May 2014) aerial surveys

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Proportion of turtle sightings with respect to benthic habitat types in: a) C1; b) IM; and Figure 4-17c) C2 during the B1 (May 2012), D2 (May 2013) and D5 (May 2014) aerial surveys

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4.1.3.3 Estimates of Turtle Population Size – Whole Blocks

Mean group sizes and correction factors used for estimating turtle population size in aerial survey blocks C1, C2 and IM during D5 are presented in Table 4-5. The PCFs and CVs calculated for turtle population size estimations ranged from 1.24 (± 0.03) for C2 to 1.31 (± 0.06) for the IM block for starboard side observations, and from 1.48 (0.06) for C2 to 1.63 (0.10) for C1 for the port side observations. The PCFs were generally lower than those calculated for the Baseline Phase, particularly for the starboard side (Cardno 2012), mainly as a result of increased recaptures between observers during D5 (between 20% and 42%; Table 4-6).

Table 4-5 Details of turtle group size estimates for whole blocks and correction factors used in population estimates for the D5 aerial surveys The following parameters were used in the Marsh and Sinclair (1989) population estimate methods only: PCF – Perception Correction Factor; CV – Coefficient of Variation. Parameter estimates were based upon all sightings in the ‘inside’ and ‘outside’ zones

Survey Block Replicate Mean group size (CV) PCF (CV)

Starboard Port

D5

C1

1 1.14 (0.13)

1.28 (0.04) 1.63 (0.10) 2 1.15 (0.13)

3 1.31 (0.00)

IM

1 1.03 (0.09)

1.31 (0.06) 1.62 (0.11) 2 1.05 (0.00)

3 1.04 (0.16)

C2^

1 1.06 (0.13)

1.24 (0.03) 1.48 (0.06) 2 1.06 (0.14)

3 --

^ Two replicate flights undertaken in C2.



Table 4-6 Sighting histories for turtles sighted during D5 aerial surveys by individual observers for each replicate flight, and all flights combined*

Block Rep. Number of turtle groups seen by: Total # turtle

groups sighted

% turtle groups sighted by both observers

PF PR PB SF SR SB Starboard Port

C1

1 16 10 5 29 12 27 99 16% 40%

2 18 8 11 35 21 24 117 30% 30%

3 12 16 8 12 14 16 78 22% 38%

IM

1 20 15 7 26 5 22 95 17% 42%

2 7 9 4 9 8 2 39 20% 11%

3 9 3 8 10 11 10 51 40% 32%

C2^

1 22 18 21 30 12 26 129 34% 38%

2 30 28 21 31 18 29 157 27% 37%

3 - - - - - - - - -

Total 134 107 85 182 101 156 765 26% 36%

Starboard front (SF); starboard rear (SR); starboard both (SB); port front (PF); port rear (PR) and port both (PB) * Replicates combined per block were used for population estimates and MARK analysis for the D5 survey ^ Two replicate flights undertaken in C2.

Due to the high number of turtle sightings across both Dredging and Baseline Phase surveys, sufficient data were available to allow population estimates to be calculated for all blocks for all replicate flights. The mean population estimates for turtles (± SE) during D5, derived using the Marsh and Sinclair (1989) method, were calculated to be 703 ± 133, 458 ± 193 and 1,013 ± 162 turtles in C1, IM and C2, respectively. These estimates were similar to those derived using the Pollock et al. (2006) method (769 ± 149, 480 ± 189 and 1,030 ± 179 turtles, respectively) (Table 4-7a, Figure 4-18, Appendix G).

Population estimates for turtles calculated using the Marsh and Sinclair (1989) and Pollock et al. (2006) methods were similar partly as a result of using the same ACF (set to ‘1’ due to the lack of an appropriate standard) for both methods. By standardising the ACF, the Pollock et al. (2006) method loses its ability to correct for spatial heterogeneity in sighting conditions for individual sightings. Using the Marsh and Sinclair (1989) method, population estimates for turtles were varied considerably between Baseline and previous Dredging Phase surveys. In C1, population estimates were slightly lower in D5, than in B3 (778 ± 165) and D2 (792 ± 218); although noticeably greater than estimates calculated for the first Baseline Phase survey B1 (335 ± 52) (Figure 4-18). Overall, the July 2012 survey (B2) had the highest estimate of turtle populations by a considerable margin (1,333 ± 788). A similar trend was evident when using the Pollock et al. (2006) method (Table 4-7).

In IM, while the turtle population estimate for D5 was comparable to D2 (412 ± 106) using the Marsh and Sinclair (1989) method, both were noticeably lower than the estimates calculated for the B1 survey (790 ± 217), as well as all other Baseline and Dredging Phase surveys (B2: 1,469 ± 890; B3: 868 ± 405; D3: 638 ± 139; and D4: 644 ± 108) (Figure 4-18). It should be noted that there are substantial error margins for these estimates, particularly for both C1 and IM estimates during B2, indicating that the estimates are quite imprecise. As with C1, a similar pattern emerged when the Pollock et al. (2006) method was used (Table 4-7).

In C2, turtle population estimates derived using the Marsh and Sinclair (1989) method were substantially greater in D5 (1,013 ± 162) than all other Baseline and Dredging Phase surveys, which ranged from 565 ± 160 for D3 to 887 ± 368 for B1. The Pollock et al. (2006) method produced an estimate for D5 that was similar to that produced by the Marsh and Sinclair (1989) method and also considerably higher than Pollock et al. (2006) estimates for all previous surveys (Table 4-7a). Overall, there were consistently higher population estimates in C2 than the other two survey blocks for both methods.



Overall, in comparison to the Baseline Phase, the Dredging Phase had lower average population estimates for turtles across all blocks (Table 4-7b). In the IM block in particular, using the Marsh and Sinclair (1989) and Pollock et al. (2006) methods, average population estimates were lower in the Dredging Phase (538 ± 173 and 520 ± 148 turtles, respectively), than in the Baseline Phase (1,061 ± 709 and 1,047 ± 851 turtles, respectively). The difference was primarily driven by the large population estimates derived by the Marsh and Sinclair (1989) and Pollock et al. (2006) methods for Rep 1 of the July 2012 survey (B2: 2,711 ± 607 and 2,770 ± 1,044, respectively) and October 2012 survey (B3: 1,428 ± 143 and 1,420 ± 129, respectively) (Appendix G).

Table 4-7 Comparison of turtle population estimates (± SE) and number of replicates where estimates were able to be derived (n) for: a) each block during B1 (May 2012), D2 (May 2013) and D5 (May 2014); and b) across the Baseline and Dredging Phases, based on Marsh and Sinclair (1989) and Pollock et al. (2006)

a) Estimation Method

B1 D2 D5

Block Estimate ± SE n Estimate ± SE n Estimate ± SE n

Marsh and Sinclair C1 335 52 2 792 218 3 703 133 3

IM 739 186 2 412 106 3 458 193 3

C2 790 217 2 626 157 3 1,013 162 3

Pollock et al. C1 350 210 2 782 242 0 769 149 2

IM 752 413 2 433 114 1 480 189 3

C2 832 585 2 720 184 1 1,030 179 3

b) Estimation Method

Baseline Phase Dredging Phase

Block Estimate ± SE n Estimate ± SE n

Marsh and Sinclair C1 875 630 8 677 205 12

IM 1,061 709 8 538 173 12

C2 831 295 8 745 243 10

Pollock et al. C1 874 730 8 643 237 12

IM 1,047 851 8 520 148 12

C2 868 485 8 747 254 10



Mean population estimates for turtles in each block during the TDMP across all surveys Figure 4-18(B1 to D5), based on: a) Marsh and Sinclair (1989); and b) Pollock et al. (2006) population estimate methodologies; and c) raw sightings data

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4.1.3.4 Turtle Densities – Whole Blocks

The density of turtles per km2 during D5 was calculated for each of the replicate flights at C1, IM and C2. The estimated mean density (± SE) of turtles in C1 was 1.02 ± 0.05 per km2 based on the Marsh and Sinclair (1989) method and 1.12 ± 0.07 per km2 based on Pollock et al. (2006) (Figure 4-19a,b). In the IM block, the estimated mean density of turtles was 0.44 ± 0.02 per km2 based on Marsh and Sinclair (1989) and 0.46 ± 0.03 per km2 based on Pollock et al. (2006). The estimated mean density of turtles in C2 was 1.04 ± 0.06 per km2 based on Marsh and Sinclair (1989) and 0.70 ± 0.06 per km2 based on Pollock et al. (2006). Based on raw sightings, the mean density of turtles was very similar in the two control blocks, with 0.80 ± 0.07 per km2 in C1 and 0.78 ± 0.08 per km2 at C2, whereas density was considerably lower in the IM block with 0.31 ± 0.08 turtles per km2.

Based on the Marsh and Sinclair (1989) method, turtle densities have shown considerable temporal and spatial variation during both Baseline and Dredging Phases (Figure 4-19a). During D5, turtle densities in C1 were marginally lower compared with D2 (1.15 ± 0.07), although substantially higher than B1 (0.42 ± 0.03). In contrast, in the IM block, turtle densities were higher in D5 than D2 (0.36 ± 0.02), but lower than densities calculated for B1 (0.61 ± 0.08). In C2, turtle densities during D5 were greater than both B1 (0.77 ± 0.06) and D2 (0.61 ± 0.06). Comparing across all surveys undertaken during the monitoring program, the highest densities of turtles were calculated for B2 in both C1 (1.57 ± 0.08) and IM (1.26 ± 0.11); while in C2 the highest densities were evident in D5.

Estimated mean population density in the three blocks based on Marsh and Sinclair (1989) indicated a comparable temporal trend to that evident for estimates using the Pollock et al. (2006) method (Figure 4-19a,b). In both there were low variability and a discernible increase in density during B1, particularly in the C1 and IM blocks, which reflected the highest densities for these blocks over both Baseline and Dredging Phase surveys using the Pollock et al. (2006) method. Based on raw sightings (Figure 4-19c), again turtle densities indicated considerable temporal and spatial variation. D5 had the highest turtle densities throughout the monitoring program in C1 and C2, with comparable to densities in D2 (0.65 ± 0.22); whereas the IM block had the lowest overall turtle densities, apart from a peak in B3.



Mean turtle density per km2 (± SE) in each block during the TDMP from B1 (May 2012) to Figure 4-19D5 (May 2014) based on: a) Marsh and Sinclair (1989); b) Pollock et al. (2006); and c) raw sightings data

0.0

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b) Pollock et al. C1C2IM

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D3July 2013

D4Oct 2013

D5May 2014

Survey

c) Raw sightings



Analysis of turtle density data derived using the Marsh and Sinclair (1989) and Pollock et al. (2006) methods found a significant Phase x Treatment interaction (Table 4-8a,b). This indicates that differences in mean density between Impact and Control Treatments were dependent on Phase (i.e. Baseline and Dredging) and vice versa (Table 4-8a,b). Subsequent pairwise comparisons carried out to further examine this interaction indicated that, despite a decline in turtle density derived using the Marsh and Sinclair (1989) method occurring in the IM block but not in either C1 or C2, no pairwise tests were significant (Table 4-8a).

Conversely, pairwise comparisons for the turtle density derived using the Pollock et al. (2006) method indicated that turtle population density was lower in the IM block compared to C1 and C2 during the Dredging Phase but not during the Baseline Phase (Table 4-8b). There were no other significant interactions or main effects involving any of the factors in either analysis. There were, however, significant differences in turtle density estimates derived from raw observations between Control and Impact treatments (p < 0.05) (Table 4-8c). Specifically, turtle population density was higher in C1 and C2 (combined) compared to IM; however, it is evident that the number of sightings has remained relatively stable in the IM block over time.



Table 4-8 Results of univariate PERMANOVA tests for differences in the density of turtles per km2 based on: a) Marsh and Sinclair (1989); b) Pollock et al. (2006); and c) raw sightings between two Phases (Baseline and Dredging), including Phase (B1, B2 and B3 within Baseline Phase; and D2, D3, D4 and D5 within Dredging Phase), two Treatments (Control and Impact) and three Blocks (C1 and C2 within Control; and IM within Impact) ( ) Terms pooled with the Residual/Pooled term in the final analysis; ^ No. permutations < 100 so Monte Carlo calculated p-value presented; significant p-values (p ≤ 0.05) in bold

Source of Variation (a) Marsh and Sinclair (1989) (b) Pollock et al. (2006) (c) Raw sightings

df MS Pseu-F p-(perm) df MS Pseu-F p-(perm) df MS Pseu-F p-(perm)

Phase 1 0.457 2.22 0.2261 1 0.6324 2.63 0.1715 1 0.0032 0.35 0.8484

Treatment 1 0.454 1.57 0.3354 1 0.4643 2.87 0.1565 1 0.2447 7.82 0.0266

Survey(Phase) 5 0.299 1.48 0.3472 5 0.3040 1.98 0.2528 5 0.1134 3.06 0.1163

Location(Treatment) 1 0.344 1.74 0.2478 1 0.1428 0.95 0.3746 1 0.0039 0.11 0.7581

Phase x Treatment 1 0.374 8.83 0.0164 1 0.2714 6.10 0.0438 1 0.1258 4.69 0.0692

Phase x Location(Treatment) 1 0.004 0.02 0.8972 1 0.0017 0.01 0.9275 1 0.0026 0.07 0.8019

Treatment x Survey(Phase) 5 0.062 0.33 0.8558 5 0.0680 0.48 0.7646 5 0.0327 0.90 0.5542

Survey(Phase) x Location(Treatment) 5 0.198 1.21 0.3140 5 0.1507 0.89 0.4765 5 0.0358 1.64 0.1727

Res 37 0.164 37 0.1684 37 0.0219

Total 57 57 57

Pairwise Comparisons (ranked from largest to smallest)

Within Baseline: Control = Impact Within Dredging: Control = Impact Within Control: Baseline = Dredging Within Impact: Baseline = Dredging

Within Baseline: Control = Impact Within Dredging: Control = Impact Within Control: Baseline = Dredging Within Impact: Baseline > Dredging

Control > Impact



4.1.3.5 Turtle Sub-block Population Estimates

During the D5 survey, turtle population estimates were calculated for each sub-block across each block (averaged across replicate flights ± SE). Around Bynoe Harbour (C1), population estimates for the four sub-blocks ranged between 37 ±13 turtles in sub-block 1 (i.e. sub-block ‘C1-1’) to 395 ± 245 for the eastern sub-block C1-3 based on the Marsh and Sinclair (1989) method. The Pollock et al. (2006) method had marginally lower estimates, ranging from 15 ± 4 turtles in sub-block C1-1 to 604 ± 106 turtles in sub-block C1-3 (Table 4-9).

The Darwin Harbour/Hope Inlet region was divided into six sub-blocks based on areas with similar bottom type and bathymetry. Population estimates ranged from 42 ± 26 turtles in the offshore IM-6 sub-block and 138 ± 35 turtles for sub-block IM-4 in Hope Inlet, using the Marsh and Sinclair (1989) method. The Pollock et al. (2006) method estimated between 57 ± 19 turtles for sub-block IM-2, which comprises the western coastline towards Charles Point, and 136 ± 41 for the IM-4 sub-block.

Within the C2 block, population estimates within the sub-blocks ranged from 168 ± 41 turtles in sub-block C2-1, to a maximum of 396 ± 74 turtles estimated for C2-3, the offshore area between the mainland and Melville Island for the Marsh and Sinclair (1989) method, and from 117 ± 27 to 389 ± 73 turtles based on Pollock et al. (2006) estimation method (Table 4-9, Appendix I).

When using the Marsh and Sinclair (1989) method, population estimates were highest overall in C2-3 and C1-2 (396 ± 74 and 395 ± 245 turtles, respectively; Table 4-9). These sub-blocks correspond with the channel between Melville Island and the mainland in block C2 (not including the Vernon Islands), and the islands to the northwest of Bynoe Harbour, respectively (Figure 4-11). Estimates were lowest in C1-1 and IM-6 (37 ± 13 and 42 ± 26 turtles, respectively), corresponding to the inner areas of Bynoe Harbour and the outermost region of the IM block. When using the Pollock et al. (2006) method, C2-3 and C1-2 had the highest population estimates; however, the estimate for C1-2 was substantially higher in (604 ± 106) when using this method compared with Marsh and Sinclair (1989). Similar to the Marsh and Sinclair (1989) method, C1-1 had the lowest estimate derived using the Pollock et al. (2006) method, while in contrast, IM-2 had the second lowest estimate (57 ± 19), corresponding to the eastern side of Cox Peninsular (Table 4-9).



Table 4-9 Turtle population estimates (± SE) for each sub-block during D5 (May 2014) based on Marsh and Sinclair (1989) and Pollock et al. (2006), averaged across replicate flights

Marsh and Sinclair (1989) Pollock et al. (2006)

Block Sub-block n* Population Estimate ± SE Population

Estimate ± SE

C1

1 3 37 13 15 4

2 3 395 245 604 106

3 3 190 65 119 36

4 3 105 55 72 32

Total 727 260 810 116

IM

1 3 89 17 112 65

2 3 94 32 57 19

3 3 119 64 123 46

4 3 138 35 136 41

5 3 112 50 102 48

6 3 42 26 103 48

Total 594 99 633 114

C2

1 2 168 41 117 27

2 2 357 81 382 73

3 2 396 74 389 73

4 2 199 47 125 22

Total 1,120 126 1,013 109

* n = number of replicate flights where ≥1 turtle sighting was recorded.

4.1.3.6 Turtle Sub-block Densities

Turtle density estimates within each sub-block (number per km2 ± SE) were calculated by dividing the derived population estimates by the total transect area sampled over water within each sub-block. Estimates for the C1 sub-block (n = 4) densities in D5 ranged between 0.13 ± 0.02 turtles per km2 for C1-1 to 0.44 ± 0.11 turtles per km2 for C1-2, based on Marsh and Sinclair (1989), and between 0.05 ± 0.01 turtles per km2 and 0.68 ± 0.13 per km2 based on Pollock et al. (2006) (Table 4-10). Mean turtle density in IM sub-blocks ranged between 0.04 ± 0.01 turtles per km2 in the offshore IM-6 sub-block to 0.43 ± 0.11 turtles per km2 for IM-5, the small sub-block closest to Gunn Point. The Pollock et al. method (2006) estimated between 0.10 ± 0.02 and 0.40 ± 0.11 turtles per km2. Within the C2 sub-blocks, the mean density ranged between 0.37 ± 0.09 turtles per km2 in the inshore region of C2-1 sub-block, and 0.86 ± 0.13 turtles per km2 in C2-2 around the Vernon Islands. The Pollock method indicated similar results with estimates of between 0.26 ± 0.05 and 0.92 ± 0.19 turtles per km2 for the same sub-blocks (Table 4-10, Appendix J).

In contrast to the population estimates, turtle densities in D5 were highest for both methods of estimation in the C2-2 sub-block, corresponding to the water around the Vernon Islands. The areas with the lowest densities varied between methods, occurring in the offshore Darwin sub-block region in IM-6 when using Marsh and Sinclair (1989), and the C1-1 sub-block of Bynoe Harbour when using Pollock et al. (2006).



Table 4-10 Turtle density estimates (per km2) for each sub-block during D5 (May 2014) based on Marsh and Sinclair (1989) and Pollock et al. (2006)


Block Sub-block Area (km²) Density Estimate ± SE Density

Estimate ± SE

C1

1 94.7 0.13 0.02 0.05 0.01

2 296.4 0.44 0.11 0.68 0.13

3 150.2 0.42 0.13 0.26 0.06

4 145.8 0.24 0.11 0.16 0.04

IM

1 193.8 0.15 0.03 0.19 0.04

2 128.7 0.24 0.09 0.15 0.03

3 121.5 0.33 0.12 0.34 0.06

4 171.5 0.27 0.05 0.26 0.05

5 85.9 0.43 0.11 0.40 0.11

6 333.1 0.04 0.01 0.10 0.02

C2

1 224.5 0.37 0.09 0.26 0.05

2 207.1 0.86 0.13 0.92 0.19

3 393.6 0.50 0.09 0.49 0.10

4 150.7 0.66 0.16 0.41 0.08

4.1.3.7 Turtle Whole Block vs Sub-block Population Estimates

During D5, population estimates for turtles derived for each whole block were lower than estimates calculated for each of the sub-blocks using either the Marsh and Sinclair (1989) and Pollock et al. (2006) methods (Figure 4-20). Based on the Marsh and Sinclair (1989) method, mean turtle population size estimates (± SE) derived for sub-blocks in C1 were 727 ± 260, 594 ± 99 for IM and 1,120 ± 126 turtles for C2 (Table 4-9, Figure 4-20a).

In the C1 block, population estimates derived from whole block analysis were comparable to those derived using sub-block estimates (703 ± 133 vs. 727 ± 260), although the level of error present for the sub-block analysis in C1 was considerably higher. In contrast, for C2 (1,120 ± 126) and IM (594 ± 99) sub-block analysis, the difference between whole block and sub-block analyses differed by more than 100 turtles, with greater margins of error evident with the whole block analyses (Table 4-9).

Mean sub-block population estimates for turtles derived using the Pollock et al. (2006) method ranged from 810 ± 116 for the C1 sub-blocks combined, 633 ± 114 in the IM sub-blocks, and 1,013 ± 109 turtles for C2 sub-blocks (Table 4-9). With the exception of C2, population estimates were marginally higher using the sub-block analyses than those derived using whole block estimates (Figure 4-20b). In C2, the mean population estimate was only slightly lower (17 turtles) when calculating estimates for sub-blocks. Overall, the error was greater when using the whole block estimates, particularly at C2 (Figure 4-20).



Mean population estimates (± SE) for turtles derived from whole block and sum of sub-Figure 4-20

block calculations based on: a) Marsh and Sinclair (1989); and b) Pollock et al. (2006) at each location for D5 (May 2014)

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4.2 Land Surveys

4.2.1 Survey Effort and Environmental Conditions

Land surveys for D5 were undertaken on two field days (14 May 2014 and 16 May 2014) from Channel Island Bridge and the rock wall at Cullen Bay. Average BSS and turbidity for each survey day at each location are presented in Table 4-11.

Both survey days were undertaken during a spring tide. The tidal changes over which sampling was conducted were 3.8 m on 14 May and 5.2 m on 16 May (Table 4-11). Raw data for each land survey period undertaken during D5 are presented in Appendix K.

Table 4-11 Survey effort for land surveys during D5 (May 2013)

Date Location surveyed Tidal window (cm)

Survey start time

Average BSS

Average Turbidity

14 May 2014 Channel Island Bridge 511 – 268 08:25 2.1 3.7

14 May 2014 Cullen Bay 638 – 261 07:15 1.3 4.0

16 May 2014 Channel Island Bridge 735 – 217 07:15 1.0 4.0

16 May 2014 Cullen Bay 734 – 220 07:25 1.6 3.9

4.2.2 Channel Island Bridge

There were 61 sightings of turtles recorded from Channel Island Bridge during D5, with 75% identified as green turtles. The remaining 25% of sightings were classified as ‘unidentified’ turtles (Table 4-12, Figure 4-21). The sighting rate was substantially lower during D5 than during 2013 surveys (D2, 115 sightings; D3, 291; D4, 194 sightings; Table 4-13). No dugongs were sighted during the D5 observation period.

Juvenile turtles accounted for 63% of the recorded sightings, with 6% considered as adults due to their size. During the second survey day in D5 (16 May 2014), there were considerably fewer turtle sightings (n = 6) compared with all other survey days completed during previous surveys at Channel Island Bridge, by an order of more than seven. During previous land surveys, the number of sightings per day ranged from 45 in D2 to 179 in D3.

4.2.3 Cullen Bay Rock Wall

At Cullen Bay rock wall, there were 54 sightings of marine megafauna recorded during D5, with 69% recorded in the north eastern quadrant (Figure 4-21). D5 had a similar number of megafauna sightings to D4 (n = 46), both of which were substantially higher than the number of recorded sightings in D3 (n = 7) and D2 (n = 2; Table 4-13). Of the 54 sightings during D5, 9% were dugongs and 91% were dolphins, with no turtles sighted at Cullen Bay rock wall.

Dugongs were sighted on three occasions (Day 1, n = 1; Day 2, n = 2). One dugong was also observed for approximately 10 mins on the western side of the wall during an ‘off-effort’ period during Day 2, which was considered likely to have been the same dugong observed during the preceding ‘on-effort’ period. Furthermore, this dugong may have also been the same individual that was observed earlier on the north-eastern side, suggesting that it had potentially remained in the area for approximately 50 mins. Dugongs have been regularly sighted at Cullen Bay during land observations in the TDMP (D3, n = 6, D4, n = 35 and D5, n = 5). It should be noted, however, that these figures are for sightings and not the number of individuals observed.

Dolphins were also sighted during both survey days at Cullen Bay, with approximately seven individuals sighted during Day 1 and about 10 dolphins on Day 2. Some dolphins displayed long dive times and irregular surfacing patterns, consistent with foraging behaviour, while others travelled slowly past the observation point. No turtles were sighted during either survey day during D5.



Table 4-12 Number of megafauna sightings and number of individual animals observed at Channel Island Bridge and Cullen Bay rock wall during D5 (May 2014) land surveys

Channel Island Bridge Day 1^ Day 2

Total sightings Individuals* Total sightings Individuals*

Unidentified turtle 10 9 5 5

Green turtle 45 34 1 1

Dugong 0 0 0 0

Dolphin 0 0 0 0

Total sightings 55 43 6 6

Cullen Bay Rock Wall

Unidentified turtle 0 0 0 0

Green turtle 0 0 0 0

Dugong 2 1 3 2

Dolphin 9 7 40 10

Total sightings 11 8 43 12

* Individuals recognised through discernable features or observation of dive behaviour ^ 3 hours of ‘on-effort’ survey time were completed during the first replicate survey at Channel Island Bridge

Table 4-13 Total number of megafauna sightings observed at Channel Island Bridge and Cullen Bay rock wall during all Dredging Phase land surveys (D2, D3, D4 and D5) N.B. Counts are of total sightings, not individuals. Land surveys were not undertaken during the Baseline Phase (2012)

Channel Island Bridge

D2 D3 D4 D5

Day 1 Day 2 Day 1 Day 2 Day 1 Day 2 Day 1 Day 2

Unidentified turtle 41 27 14 0 10 69 10 5

Green turtle 25 13 98 179 71 13 45 1

Dugong 0 0 0 0 0 0 0 0

Dolphin 4 5 0 0 31 0 0 0

Total sightings 70 45 112 179 112 82 55 6 Cullen Bay Rock Wall Unidentified turtle 0 1 0 0 0 4 0 0

Green turtle 1 0 0 0 0 7 0 0

Dugong 0 0 1 5 0 35 2 3

Dolphin 0 0 1 0 0 5 9 40

Total sightings 1 1 2 5 0 51 11 43 Tidal movement (m) 2.1 5.1 1.6 1.3 0.7 4.5 3.8 5.2



Distribution of megafauna sighted during land surveys in D5 (May 2014) Figure 4-21N.B. Points indicate the initial sighting of an individual or group; multiple animals made during a single sighting are denoted by one dot as animals are recorded at the same location



4.3 QA/QC for Aerial and Land Surveys Within the aerial survey observer database, a total of 343 line entries were quality checked, with four errors detected (1.2 %). As part of the environmental database quality control check, 232 line entries were checked, with no errors detected. During the master database quality check 1,653 entries were checked, with 37 errors identified (2.2%). All errors were subsequently corrected.

All entries in the land-based survey observer database were checked against the datasheets for quality assurance and a total of three data entry errors (8% of total records) were found. All errors were subsequently corrected.

4.4 Turtle Tagging

4.4.1 Turtles Tagged

One juvenile green turtle was successfully caught and tagged with a satellite transmitter and flipper tag in November 2012, with detailed results reported in the Routine Turtle and Dugong Monitoring Program - Dredging Report 1 (Cardno 2013b).

The 2013 tagging events resulted in the successful capture of four juvenile turtles, three of which were suitable for satellite and flipper tagging (Table 4-14). A juvenile hawksbill was successfully captured during the November 2013 tagging trip; however, it was released without tagging as it was of an insufficient size (2.3 kg) for flipper or satellite tag attachment.

Table 4-14 Summary of juvenile turtles captured during the November 2013 and December 2013 tagging events

Tag Date Turtle Tag ID # Turtle Name Species Weight (kg)

15 November 2012 120875 Malakai Green (Chelonia mydas) 28.0

5 November 2013 -- -- Hawksbill* (Eretmochelys imbricata) 2.3

6 November 2013 120866 Pepin Green (Chelonia mydas) 9.1

5 December 2013 120872 Chloe Green (Chelonia mydas) 8.2

6 December 2013 120868 Hendrix Green (Chelonia mydas) 11.7

* Turtle unsuitable for satellite tagging due to small size.

The first turtle suitable for the tagging program, ‘Malakai’, was netted on 15 November 2012; however following tagging, there was insufficient data collected (i.e. limited location and dive data received) to determine range, movements and dive patterns of this turtle (Table 4-14). The second turtle suitable for the tagging program was netted on 6 November 2013. This sub-adult green turtle (named ‘Pepin’ by the field team, Tag # 120866) weighing 9.1 kg, was fitted with a satellite transmitter, flipper tagged and released from the Channel Island boat ramp (Figure 2-4). ‘Chloe’ (Tag # 120872), the smallest green turtle to be captured during the TDMP weighing 8.2 kg, was successfully tagged (satellite transmitter only) and released on 5 December 2013 from Channel Island boat ramp. No flipper tag was secured to this turtle due to the small size and the possible interference of the tag during swimming and foraging. The fourth turtle tagged in 2013 was ‘Hendrix’ (Tag #120868), a juvenile green turtle weighing 11.7 kg, that was fitted with a satellite transmitter and flipper tag and released on 6 December 2013 from the Channel Island boat ramp.

4.4.2 Ranges and Patterns of Movements of Tagged Turtles

Pepin (Tag #120866) ‘Pepin’ was tagged on 6 November 2013 with the last recorded Fastloc GPS location point received on 22 April 2014. A total of 484 ARGOS locations and 193 solved Fastloc GPS locations were recorded over a 168-day tracking period. The accuracy of location data was relatively good, with an average number of



satellites (used to process each solved fast-GPS location data point) recorded at 4.7. Of the ARGOS locations (n = 484), 92% were categorised as Class ‘B’ quality (refer to Section 2.5.3) and 5.8% were categorised as Class ’A’. Each location class ‘0’, ‘1’, ‘2’ and ‘3’ had less than 1% of ARGOS location points, which suggests a low confidence level of accuracy of location data (see Section 2.5.3 for location class classifications). Movement patterns indicate that Pepin travelled to the southern end of the channel between Channel Island and the mainland after being released, approximately 3 km from the capture site off the east side of Channel Island. GPS location data suggests movement patterns within an approximate 1.3 km2 area, consistent with mangrove, intertidal and reef habitats, ranging in depths of up to 5 m (Figure 4-22).

During this period tagging data indicates that, while Pepin generally remained within a defined home range, there were some short-term movements away from this site; the turtle travelled approximately 5 km towards the north western side of Channel Island on 11 November 2013 and again on the 21 February 2014, towards Wickham Point wharf. The last solved fast-GPS location for Pepin indicated that the turtle was approximately 1.5 km southeast of Channel Island Bridge, close to the mangroves.

Hendrix (Tag #120868)

Satellite transmissions of GPS location data for ‘Hendrix’ ceased on 13 March 2014 (Figure 4-23). The average number of satellites processing each solved Fastloc GPS location data point recorded was 5.2, with 5.6% and 92.5% of ARGOS locations classified as ‘A’ and ‘B’ quality, respectively. Only 1.5% of ARGOS locations were categorised as Class ‘1’, ‘2’ or ‘3’, which suggests a low confidence level of accuracy of location data; however, 31.3% of all location data points recorded were classified as GPS derived points which had accuracy to 100 m.

During the tracking period, 421 ARGOS locations and 194 solved Fastloc GPS locations were recorded for Hendrix, with dive depth and duration data recorded up to 4 April 2014. Tracking data indicated that this turtle remained close to the southern end of Channel Island, approximately 500 m from known mangrove habitats. Patterns of movements indicated frequent traversing through the channel to each end, predominantly around mangroves and reef habitats covering a range of approximately 1.5 km2 (Figure 4-23). Similar to Pepin, Hendrix travelled away from its normal defined range close to Channel Island Bridge on two occasions, moving approximately 1.5 km southwest of the island where it remained for five days, before returning to the southern channel, with the last recorded location close to the southern side of Channel Island Bridge.

Chloe (Tag # 120872)

Satellite transmissions of GPS location data for ‘Chloe’ ceased on 4 March 2014, with dive duration data and dive depth ceasing on 28 February 2014 and 1 March 2014, respectively. During the tracking period, 294 ARGOS locations and 69 solved Fastloc GPS locations were recorded. The average number of satellites processing each solved Fastloc GPS location data point recorded was 5.4 and a majority (96.6%, n = 284) of the ARGOS locations obtained classified as ‘B’ quality locations, indicating only two messages were received by passing satellites to process tag information. Only five locations were within the ‘A’ quality (three messages received), and one location each for ‘0’ (accuracy of location over 1,500 m), ‘1’ (accuracy of location within 1,500 m) and ‘2’ (accuracy of location within 500 m) quality (four messages or more received), which suggests a low confidence level of accuracy of location data.

Patterns of movement showed that in the days following release, Chloe travelled southwest from Channel Island towards the western side of Middle Arm, then northwest towards the West Arm of Darwin Harbour, before returning to Channel Island after a week (Figure 4-24). Tracking data indicated that Chloe’s usual movement patterns were limited to a range of < 1 km2, and primarily within a 500 m area on the southern side of Channel Island Bridge, consistent with macrobiota, hard coral reef and mangrove habitats. The last recorded location for Chloe was at the southern end of Channel Island, within mangrove habitat, approximately 800 m southwest from Channel Island Bridge.



Transmitted geo-locations of ‘Pepin’, satellite tagged on 6 November 2013. Dots indicate movement recorded between 6 November 2013 Figure 4-22and 22 April 2014



Transmitted geo-locations of ‘Hendrix’, satellite tagged on 6 December 2013. The dots indicate movement patterns, recorded between Figure 4-236 December 2013 and 13 March 2014



Transmitted geo-locations of ‘Chloe’, satellite tagged on 5 December 2013. The dots indicate movement patterns for data from Figure 4-245 December 2013 to 4 March 2014



4.4.3 Depth and Duration of Turtle Dives

During the TDMP, most dives (68%) recorded from the four tagged turtles were less than 15 mins in duration and, of these, 26% of dives were between 11 and 15 mins (Figure 4-25). There was a steady decrease in the frequency of dives of increasingly longer duration. Most dives were undertaken in shallower depths (Figure 4-26), with the majority to a depth of 5 m or less. Very few dives (i.e. < 1%) reached depths of greater than 11 m.

The first tagged turtle in November 2012, ‘Malakai’, transmitted limited location and dive data to determine range, movements and dive patterns of this turtle. Pepin recorded a total of 2,476 dives during the 168-day tracking period, with over 96% of dives being shallow and not exceeding 5 m in depth. The remainder of dives were in the 6 m to 10 m depth range. There were a similar amount of dives with a duration of 0 to 5 mins, 6 to 10 mins and 11 to 15 mins, although the greatest number of dives for this turtle were in the 11 to 15 mins category (24%, n = 613) and only 5% of dives were over 60 mins (n = 132).

Hendrix recorded 2,850 dives over the tracking period, with 99% (n = 2,812) of these dives being shallow and not exceeding 5 m in depth. A further 1% of dives occurred between 6 m to 10 m, and only three dives occurred at a depth of between 11 m to 15 m; no dives were recorded below 15 m. The majority of dives (70%) were between 5 and 15 mins in duration (n = 1,964), with only 4% of dives recorded over 60 mins.

Chloe recorded 910 dives, with 65% (n = 593) of these being shallow and not exceeding 5 m in depth. A further 33% (n = 296) of dives were between 6m to 10 m in depth, with the remaining 2% (n = 21) greater than 11 m in depth. The majority of dives (28%, n = 214) were for 11 to 15 mins, 24% (n = 184) were 6 to 10 mins and 18% for 0 to 5 mins. Only 4% (n = 30) were greater than 60 mins in duration.

Proportion of dives for specific durations (min) for turtles tagged during the November Figure 4-252013 and December 2013 tagging events

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Proportion of dives for specific depths (m) for turtles tagged during the November 2013 Figure 4-26and December 2013 tagging events

4.4.4 Rehabilitated Turtles

A summary of all rehabilitated turtles (current and past) reported to Cardno by the Arafura Timor Research Facility or the Department of Land Resource Management since the commencement of the TDMP is provided in Appendix L. To date, rehabilitated turtles have included one olive ridley, six flatback, three hawksbill and three green turtles (n = 13).

The most recent rehabilitated turtle was found in March 2014. This was an adult female hawksbill that was rescued from a fishing vessel apprehended by the Australian Fisheries Management Authority (AFMA) near Evans Shoal, 250 km north of Darwin and taken to Animal Ark Hospital. This turtle, named ‘Linh’, was fitted with a satellite transmitter and flipper tag following its recovery and was released on 27 March 2014 by DLRM at Nightcliff Jetty, Darwin. Initially, Linh travelled approximately 80 km offshore from the site of release into the Beagle Gulf, before tracking back closer to shore. As of 10 June 2014, Linh has been spending the majority of time in waters north east of Darwin, within approximately 30 km of shore; at the time of writing this report Linh’s tag was still transmitting GPS data.

Over the 76 days of tracking, Linh’s dive depth profiles have remained largely consistent, although considerably different from the four tagged juvenile green turtles (Figure 4-26, Section 4.4.1). As of early June 2014, the majority of Linh’s dives (61%, n = 650) were greater than 26 m depth, 42% of which occurred in the 31 m to 40 m depth category. Only 29% of dives occurred in the 0 m to 5 m depth category, where the majority of the juvenile green turtle dives were undertaken, with minimal dives (6%, n = 63) in the deeper depth categories. Dive duration profiles indicated that the majority of dives for Linh were less than 5 mins (21%, n = 147). This was followed closely by dives greater than 60 mins (19%, n = 132), then dives within the 31 mins to 40 mins category (13.3%, n = 93). This was comparable to the dive profiles of the juvenile green turtles; however, Linh has shown more evenly defined peaks in both the short and long extremes of dive duration categories.

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Proportion of dives for specific durations (min) for tagged rehabilitated turtle ‘Linh’ Figure 4-28

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Transmitted geo-locations of ‘Linh’, satellite tagged on 27 March 2014. Dots indicate movement patterns recorded between 27 March Figure 4-29

2014 and 10 June 2014



5 Discussion

The TDMP incorporates various visual survey techniques to estimate and monitor turtle and dugong populations within Darwin Harbour (IM), Hope Inlet (IM), Shoal Bay (IM), Bynoe Harbour (C1) and waters between the mouth of the Adelaide River and Melville Island, including the Vernon Islands (C2). The TDMP has been undertaken routinely throughout the Baseline and Dredging Phases of the Project, with data compiled during the Dredging Phase compared with those collected prior to the commencement of dredging and construction activities (B1, May 2012; B2, July 2012; B3, October 2012). Dredging Phase surveys were undertaken during the dry season dredging hiatus following the completion of Season One dredging (D2, May 2013; D3, July 2013; D4, October 2013), and toward the end of GEP and Season Two EA dredging (D5, May 2014). The D5 survey took place approximately six months after the commencement of Season Two dredging operations in October 2013 (GEP) and November 2013 (EA) and was the final Dredging Phase survey. At the completion of D5, the EA dredging component of the Project was approximately 97% complete. This End of Dredging Report outlines the results from the D5 survey and summarises the results of the Dredging Phase surveys undertaken as part of the TDMP. To date, all Dredging Phase monitoring objectives have been achieved.

5.1 Dugongs During the monitoring program, there have been fluctuations between surveys in both raw sightings and the estimates of abundance derived from these, although no trends (including seasonal) have been evident, suggesting that abundance is fluctuating about a mean at all three locations (C1, IM and C2). Abundances of dugongs at the three locations during the Baseline Phase ranged between 157 and 411 dugongs (as estimated using the Marsh and Sinclair (1989) method) or between 95 and 273 dugongs (Pollock et al. (2006)). During the Dredging Phase, abundances ranged between 93 and 382 (Marsh and Sinclair (1989)) and between 41 and 274 (Pollock et al. (2006)). Despite the variability, significant statistical differences in sightings among the surveys were not detected. There were, however, statistical differences among surveys in dugong densities (derived using the Marsh and Sinclair (1989) method), but it was not possible to determine for which locations these differences occurred. Sightings and estimates of abundance in D2 were the lowest during any of the Dredging or Baseline Phase surveys for the IM (Darwin Harbour/Hope Inlet to Gunn Point) and C1 (Bynoe Harbour) locations, and the second lowest for C2 (Gunn Point, around the Vernon Islands and across to Melville Island). In C2, sightings and estimates of abundance during D5 were the highest of any TDMP survey, while in C1 and IM they were consistent with earlier surveys.

Sightings of dugongs over time were generally higher in the IM block compared to C1 and C2, with the exception of D5 (where C2 had the greater number of sightings) and D2 (where sightings in all three locations were similar). Estimates of dugong abundance followed a similar pattern. Although there were very few sightings of calves compared to adults (i.e. seven calves at most in any survey), most calves were sighted in IM. However, as dugongs have a low fecundity due to a highly inconsistent reproductive rate, few calves were expected to be seen during aerial surveys.

Spatial variability has also been observed within all locations throughout the Baseline and Dredging Phase surveys. The bathymetric data indicated a higher frequency of sightings of dugongs in shallow areas (6 m to 10 m depth) of all three locations; with increased variability in sightings further from the shore (i.e. there were greater densities in shallow, inshore regions). While the positions of aggregations varied between surveys, there were recognised ‘hotspots’ often in waters surrounding offshore islands or close to shore, including near Grose, Indian and Bare Sand islands in C1, in the shallow areas surrounding the Vernon Islands in C2 and around Fannie Bay, Casuarina Beach, and around Shoal Bay in IM. Within IM, very few dugongs have been seen within Darwin Harbour Inner in the Baseline or Dredging Phases.

The observed variability in dugong sightings among surveys and spatial patterns within locations and among replicate aerial flights probably resulted from a number of factors, including movement of dugongs in search of optimum foraging areas and the seasonal variation in the density and distribution of seagrass habitats. Dugongs are dependent on seagrass for food (Preen 1992). Migration of dugongs among areas is largely believed to be due to their search for suitable seagrass beds and/or warmer waters (Marsh et al. 2002). Distribution and density of mapped Halophila and Halodule, a preferred seagrass food source sought by



dugongs (Anderson 1998), has varied substantially within Darwin Harbour over the duration of the TDMP (Cardno 2014b). Seagrass has been consistently present at Fannie Bay and Casuarina Beach, as well as off Lee Point, although the size and cover of seagrass within these beds has been highly variable between surveys. The locations of these seagrass beds appear to correlate with the observed dugong hotspots in shallow areas, while the temporal changes in the size and cover of these beds may explain some of the inter-survey variation in dugong sightings. It is difficult to conclusively determine whether there has been a strong correlation between the density and distribution of dugong and seagrass habitat throughout IM, particularly given that dugong densities have often been highest through Shoal Bay, including some areas outside the boundaries of the seagrass monitoring program.

TDMP aerial surveys were undertaken only in the dry season as wet season conditions are generally not suitable for aerial surveys; however, following the completion of surveys throughout the Baseline and Dredging Phases, there are no indications of any major spatial or temporal changes in the distribution or relative abundance of dugongs in the Darwin region that could potentially indicate an effect of dredging.

5.2 Turtles Similar to dugongs, there have been fluctuations between surveys in raw sightings for all three locations, although no temporal trends have been evident suggesting that, as for dugongs, abundance at all three locations is fluctuating about a mean. During the TDMP there have been considerable numbers of turtles observed around the surveyed areas. Estimates of abundance for turtles at the three locations during the Baseline Phase ranged between 335 and 1,469 turtles (as estimated by the Marsh and Sinclair (1989) method) and, similarly, between 350 and 1.437 turtles using the Pollock et al. (2006) method. During the Dredging Phase, abundances ranged between 412 and 1,013 turtles (as estimated by the Marsh and Sinclair (1989) method), and between 433 and 1,030 turtles (Pollock et al. (2006)). In most Baseline and Dredging Phase surveys, sightings and estimates of abundance of turtles in the IM location appeared similar to those in C1 and C2, apart from D5 where the sightings of turtles in the Control locations were much higher than for IM and the highest seen throughout the TDMP. This high number of sightings in the Control locations during D5 contributed in part to the significant statistical difference in densities of turtles (based on raw sightings) between Control locations and IM, across all surveys combined.

A decrease in the density of turtles was also detected for the IM location between the Baseline and Dredging Phases. Again this is in part due to D5, where the sightings and estimates of abundance of turtles in the Control locations were much higher than in IM, but it is also due to high estimates of abundance for turtles in B2 for all locations. The Marsh and Sinclair (1989) and Pollock et al. (2006) methods for estimating population size and density are potentially prone to error where there are low recapture rates (i.e. when the second observer in the aircraft does not observe the turtle seen by the first observer). In B2, the PCFs were unusually high for all locations as a consequence of low recapture rates and hence big population sizes of turtles for that survey were estimated for all locations, despite there being a very small number of sightings in that survey. As similarly high PCFs were not seen in other surveys, it is considered that the decrease in density of turtles at the IM location between the Baseline and Dredging Phases is an artefact of the population estimate methodology, rather than being an actual change in abundance of turtles in IM.

Sightings of turtles over time were generally lower in the IM block compared to the Control locations, with the exception of the B1 survey, where C2 had the least number of sightings and B2, where sightings in IM were similar to C1. It is not clear what has been driving these differences among locations or the fluctuations among surveys, but it is potentially due to a combination of factors, including movement of turtles in search of optimum foraging areas and, for some of the areas, potentially the influx of nesting turtles at times. Aerial surveys do not allow identification of individual turtle species, and it was not possible to determine whether there have been influxes of nesting turtles of a particular species at particular times of year. In the known June to September nesting period, significant numbers of flatback and some olive ridley turtles are known to nest in parts of C1 (Bare Sand and Quail Islands), as well as smaller numbers in C2 (Indian Island, southern parts of Melville Island and on the far west banks of the mainland) and IM (Casuarina beach and Cox Peninsular) (Chatto and Baker 2008). Aerial surveys undertaken during that nesting period have had limited temporal coverage as they have taken place in July which is early on in the nesting period. Numbers of sightings of turtles at these times have generally been among the lowest for the Baseline and Dredging surveys for all three locations, and hence do not provide evidence of an influx of nesting turtles.



Where it was possible for observers to identify the species of turtle sighted in land- and boat-based surveys (B1 and B2 for boat-based surveys and D2 to D5 for land-based surveys), green turtles have been the predominant species reported. Boat and land-based surveys have generally been close to the coast and green turtles would be expected in these areas due to their mainly marine plant diet (i.e. seagrass and marine algae only grow in shallow areas). However, in the aerial surveys, turtles were also regularly sighted in areas further offshore in all three locations. As these deeper habitats would be unlikely to contain marine plants, the turtles sighted are likely to have been hawksbill or flatback turtles, whose diet includes sponges and soft corals that are thought to grow on the soft sediment in these habitats (NAILSMA 2006). Indeed, the tagged adult hawskbill turtle Linh released at Nightcliff Jetty moved quickly offshore and was regularly recorded diving as deep as 40 m, probably in search of food on the seabed. In contrast to Linh, available evidence suggests that the four juvenile green turtles tagged and released at Channel Island remained close to the capture area for the duration of satellite tag transmissions (i.e. up to 168 days), remaining within a small home range of between approximately 1 km2 and 1.5 km2. The juvenile green turtles appeared to utilise shallow habitats around Channel Island, including areas of reef and mangroves where they were probably foraging on marine algae. Notwithstanding the broad distribution of turtle sightings in the three locations, the most sightings occurred in the areas surrounding the islands to the north of Bynoe Harbour in C1 (of which Dum In Mirrie Island is recognised as an important feeding ground for sub-adult green and hawksbill turtles (Chatto and Baker 2008)), shallow waters around the Vernon Islands and Melville Islands in C2, and west of Gunn Point and around Casuarina Beach in IM.

Following the completion of Baseline and Dredging Phase aerial surveys, although spatial and temporal variation has been observed in the distribution and abundance of turtles over the duration of the monitoring program, these differences are likely to be a result of natural variation. Similar to dugongs, the distribution and relative abundance of turtles was ascertained in the TDMP only in the dry season as wet season conditions are generally not suitable for aerial surveys. However, finer scale aspects of turtle behaviour were able to be established in the wet season from sampling carried out as part of the turtle tagging component of the monitoring program. These data indicated that turtles stayed within Darwin Harbour Inner during the months their satellite tags were transmitting in the Dredging Phase.



6 Conclusion

The Turtle and Dugong Monitoring Program (TDMP) was designed using standardised survey techniques to gain a more comprehensive understanding of spatial and temporal patterns in the distribution and relative population abundance of dugongs and turtles in Darwin Harbour and surrounding locations.

Aerial surveys undertaken throughout the Dredging Phase (i.e. D2: May 2013, D3: July 2013, D4: October 2013 and D5: May 2014) have been appropriate for the collection of broad-scale data to meet the main objective of the monitoring program and the broad objectives of the TDMP. While there have been fluctuations among surveys in both the raw sightings of dugongs and the population abundance estimates derived from these, no clear spatial or temporal trends (including seasonal) were evident suggesting that abundance fluctuated about a mean across all three surveyed locations. There was a higher frequency of dugong sightings in shallower regions (0 m to 10 m water depth) across the entire surveyed area, although very few dugongs were sighted within Darwin Harbour Inner during either the Baseline or Dredging Phases. Similar to dugongs, considerable temporal and spatial variation was observed in the abundance of turtles across surveyed locations, although no temporal trends were evident, suggesting that the abundance of turtles at all three locations fluctuated about a mean. The observed variability in turtle and dugong sightings among surveys and smaller-scale spatial patterns within locations probably resulted from a number of factors, including movement in search of optimum foraging areas and seasonal variation in the density and distribution of seagrass habitats.

Land surveys were aimed at providing finer-scale spatial, temporal and behavioural data on turtles and dugongs at ‘hotspots’ around Darwin Harbour. Results were similar across most Dredging Phase surveys, with considerably more sightings of turtles (predominantly green turtles) around Channel Island compared with Cullen Bay rock wall, where most sightings were of dugongs and dolphins. A pattern of consistent observation of these species across surveys, and in close association with mapped seagrass habitats, strongly suggests they use these areas for foraging.

Tagging and tracking of juvenile turtles was carried out in Darwin Harbour, with the successful acquisition of data from this component of the TDMP enabling the objective to be achieved of ‘assessing fine-scale aspects of dugong and turtle populations within Darwin Harbour in relation to potential habitat use and identify foraging areas’. Four juvenile green turtles tagged and released at Channel Island during the TDMP appeared to have discrete home ranges, remaining within a small area of approximately 1.5 km2. These turtles utilised shallow habitats around Channel Island including areas of reef and mangroves, probably using them as foraging habitats.

While spatial and temporal variation has been observed in the distribution and abundance of turtles and dugongs over the duration of the TDMP, on the balance of evidence, these differences are most likely the result of natural variation. As there were no major changes detected to either turtle or dugong populations during the Dredging Phase, long-term Post-dredging Phase monitoring is not considered to be necessary for the TDMP.



7 Acknowledgements

This report was written by Dr Michelle Blewitt, Freya Muller and Ivon Sebastian, with assistance of Dr Andrea Nicastro, and reviewed by Dr Craig Blount and Dr Will Macbeth. GIS support was provided by Shani Archer, with assistance from Amy Steiger. Data analysis was undertaken by Dr Andrea Nicastro, Dr Michelle Blewitt, and Freya Muller, with the assistance of Dr Lachlan Barnes. The figures, tables and appendices were prepared by Freya Muller and Dr Andrea Nicastro.

Fieldwork for the D5 surveys was undertaken by Dr David Waayers, Dr Glenn Dunshea, Barry Krueger, Paul Tod and Megan Ridgway, with Freya Muller as a trainee. Turtle tagging fieldwork, undertaken in November 2013 and December 2013, was undertaken by Megan Rice, Paul Tod, Barry Krueger and David Kozak from INPEX.

Logistical and communications support during D5 field sampling was provided by Erica Griffiths from Sydney, Todd Sinclair in the Cardno office in Darwin, and Skye Stevens based in Perth.



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Anderson, M.J. (2001). A new method for non-parametric multivariate analysis of variance. Austral Ecology, 26, pp. 32-46.

Australian Hydrographic Service (2003). AUS 26 − Approaches to Port Darwin.

Australian Hydrographic Service (2007). AUS 24 − Port Darwin Wickham Point.

Australian Hydrographic Service (2009a). AUS 27 − Port Darwin Middle Arm - Including Channel Island.

Australian Hydrographic Service (2009b). AUS 28 − Port Darwin East Arm.

Bayliss, P. and Freeland, W.J. (1989). Seasonal distribution and abundance of dugongs in the Western Gulf of Carpentaria. Australian Wildlife Research, 16, pp. 141-149.

Cardno (2012). Turtle and Dugong Monitoring Program Baseline Report. Ichthys Nearshore Environmental Monitoring Program. Prepared for INPEX. Cardno (NSW/ACT) Pty Ltd, Sydney.

Cardno (2013a). Nearshore Environmental Monitoring Plan (Rev. 4). Prepared for INPEX. Cardno (NSW/ACT) Pty Ltd, Sydney.

Cardno (2013b). Routine Turtle and Dugong Monitoring Program Report – Dredging Report 1. Ichthys Nearshore Environmental Monitoring Program. Prepared for INPEX. Cardno (NSW/ACT) Pty Ltd, Sydney.

Cardno (2013c). Routine Turtle and Dugong Monitoring Program Report – Dredging Report 2. Ichthys Nearshore Environmental Monitoring Program. Prepared for INPEX. Cardno (NSW/ACT) Pty Ltd, Sydney.

Cardno (2013d). Routine Turtle and Dugong Monitoring Program Report – Dredging Report 3. Ichthys Nearshore Environmental Monitoring Program. Prepared for INPEX. Cardno (NSW/ACT) Pty Ltd, Sydney.

Cardno (2014a). Routine Turtle and Dugong Monitoring Program Report – Dredging Report 4. Ichthys Nearshore Environmental Monitoring Program. Prepared for INPEX. Cardno (NSW/ACT) Pty Ltd, Sydney.

Cardno (2014b). Quarterly Seagrass Monitoring – Dredging Report 6. Ichthys Nearshore Environmental Monitoring Program. Prepared for INPEX. Cardno (NSW/ACT) Pty Ltd, Sydney.

Chatto R. and Baker B. (2008). The distribution and status of marine turtle nesting in the Northern Territory, Technical Report 77/2008, Prepared for Parks and Wildlife Services, Northern Territory.

Chilvers, B.L., Delean, S., Gales, N.J., Holley, D.K., Lawler, I.R., Marsh, H. and Preen, A.R. (2004). Diving behaviour of dugongs, Dugong dugon. Journal of Experimental Marine Biology and Ecology, 304, pp. 203-224.

Costa, D.P., Robinson, P.W., Arnould, J.P.Y., Harrison, A.-L., Simmons, S.E. (2010). Accuracy of ARGOS locations of pinnipeds at-sea estimated using Fastloc GPS. PLoS ONE 5(1).

Fuentes, M.M., Lawler, I. R. and Gyuris, E (2006). Dietary preferences of juvenile green turtles (Chelonia mydas) on a tropical reef flat. Wildlife Research, 8, pp. 671–678.

GeoOceans (2012). Ichthys Nearshore Environmental Monitoring Program: Seagrass Habitat Monitoring Survey, October 2012. Technical Report. Prepared for Cardno on behalf of INPEX.

GeoOceans (2013a). Ichthys Nearshore Environmental Monitoring Program: Seagrass Habitat Monitoring Survey, May 2013. Technical Report. Prepared for Cardno on behalf of INPEX.

GeoOceans (2013b). Ichthys Nearshore Environmental Monitoring Program: Seagrass Habitat Monitoring Survey, November 2013. Technical Report. Prepared for Cardno on behalf of INPEX.

GeoOceans (2014). Ichthys Nearshore Environmental Monitoring Program: Seagrass Habitat Monitoring Survey, May 2014. Technical Report. Prepared for Cardno on behalf of INPEX.

Hodgson, A., Marsh, H., Marsh, L., Grech, A., McMahon, A. and Parra, G. (2011). Dugong Aerial Survey Manual. James Cook University, Townsville.

INPEX (2011). Ichthys Gas Field Development Project- Draft Environmental Impact Statement. INPEX Operations Australia Pty Ltd.

INPEX (2013). Dredging and Spoil Disposal Management Plan – East Arm Rev 4. INPEX Operations Australia Pty Ltd.

INPEX (2014). Dredging and Spoil Disposal Management Plan – Gas Export Pipeline Rev 7. INPEX Operations Australia Pty Ltd.



Lanyon, J. (2007). Determining critical reproductive parameters for a subtropical dugong population. Report to the Australian Centre For Marine Mammal Science, Australian Antarctic Division.

Limpus, C.J. (2008). Green turtle, Chelonia mydas (Linnaeus). In: A Biological Review of Australian Marine Turtles. Queensland Government Environmental Protection Agency.

Marsh, H. (1999). Reproduction in sirenians. In: Biology of Marine Mammals. J.E. Reynolds, III and S.A. Rommel, eds. pp. 243-256. Smithsonian Institution Press.

Marsh, H. and Sinclair, D.F. (1989). Correcting for visibility bias in strip transect aerial surveys of aquatic fauna. Journal of Wildlife Management, 53, pp. 1017-1024.

Marsh, H., Penrose, H., Eros, C. and Hughes, J. (2002). Dugong: status reports and action plans for countries and territories in its range. Cambridge, UK: IUCN.

Meylan, A. (1988). Spongivory in hawksbill turtles: A diet of glass. Science, 8, pp. 393-395.

NAILSMA (2006). Dugong and marine turtle knowledge handbook. North Australian Indigenous Land and Sea Management Alliance. Feb 2006. 132 pp.

Pollock, K., Marsh, H., Lawler, I. R. and Alldredge, M.W. (2006). Estimating animal abundance in heterogeneous environments: an application to aerial surveys for dugongs. Journal of Wildlife Management, 70, pp. 255-262.

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Whiting, S.D. (2000). ‘The ecology of immature green and hawksbill turtles foraging on two reef systems in northern Australia’, PhD Thesis. Northern Territory University, Darwin.

Whiting, S.D. (2001). Preliminary observations of dugongs and sea turtles around Channel Island, Darwin Harbour. Report to Power and Water Authority, Darwin.

Whiting, S.D. (2002). Rocky reefs provide foraging habitat for dugongs in the Darwin region of northern Australia. Australian Mammalogy, 24, pp. 147-150.

Wilkinson, C. R. and Evans, E. (1989). Sponge distribution across Davies reef, Great Barrier Reef, relative to location, depth and water movement. Coral Reefs 8, pp. 1-7.

Routine Turtle and Dugong Monitoring Program Report – Dredging Report 5 Ichthys Nearshore Environmental Monitoring Program


Ichthys Nearshore Environmental Monitoring Program

APPENDIX A SUMMARY OF AERIAL SURVEY EFFORT DURING BASELINE AND DREDGING PHASE SURVEYS



Appendix A Summary of aerial survey effort for each block (C1, IM and C2) during Baseline (B1, B2 and B3) and Dredging Phase (D2, D3, D4 and D5) surveys

Baseline Survey Period Number of transects Total length

transectsª (km) Total sampled area

(km²) Overall surveyed

area (km²) Proportion

surveyed* (%) Average survey

duration (h:mm:ss)

Bynoe Harbour

(C1)

B1 20 299.50 119.80 598.08 20.03 0:54:17

B2 20 350.30 140.12 693.45 20.21 1:23:23

B3 20 349.88 139.95 688.17 20.34 1:27:53

D2 20 349.88 139.95 688.17 20.34 1:06:32

D3 20 – 22^ 348.37 – 344.94^ 139.35 – 137.98^ 687.03 20.28 – 20.08^ 1:58:20

D4 20 348.37 139.35 687.03 20.28 1:50:29

D5 20 348.37 139.35 687.03 20.28 1:45:55

Darwin Harbour

(IM)

B1 29 524.40 209.76 1029.43 20.38 1:25:47

B2 27 517.40 206.96 1024.05 20.21 1:25:36

B3 27 517.72 207.09 1019.58 20.31 1:26:55

D2 27 517.72 207.09 1019.58 20.31 1:36:53

D3 27 519.26 207.70 1034.49 20.08 2:47:28

D4 27 518.01 207.21 1034.49 20.03 2:43:22

D5 27 518.01 207.21 1034.49 20.03 2:43:10

Vernon Islands

(C2)

B1 21 469.60 187.84 929.35 20.21 1:36:17

B2 22 491.90 196.76 971.84 20.25 1:12:08

B3 22 492.04 196.82 969.83 20.29 1:20:36

D2 22 492.04 196.82 969.83 20.29 1:15:09

D3 22 – 19^ 492.01 – 482.85^ 196.80 – 193.14^ 975.91 20.17 – 19.79^ 2:28:04

D4 22 492.01 196.80 975.91 20.17 2:24:33

D5 19 482.85 193.14 975.91 19.79 2:24:25

ª Transect length over water. * The proportion of surveyed area is averaged in the calculation of total area surveyed; B1 = 2 replicates; B2, B3, D3 and D4 = 3 replicates; D2 and D5 = 2 replicates of C2, 3 replicates of C1 and IM. ^ Variation due to flight orientation.




APPENDIX B SUMMARY OF DUGONG SIGHTINGS ACROSS DREDGING AND BASELINE PHASE SURVEYS



Appendix B Summary of the number of dugongs recorded during Baseline Phase (B1, B2 and B3) and Dredging Phase (D2, D3, D4 and D5) surveys All areas Total sightings

Survey period D5 B1 B2 B3 D2 D3 D4

Replication number R1 R2 R3 Total

Number of observations 31 32 12 75 45 62 81 28 52 64

Number of animals 41 41 15 97 58 92 113 33 71 87

Number of calves 2 1 0 3 4 7 2 1 4 7

Maximum group size 2 4 3 4 3 4 7 3 4 4

Bynoe Harbour (C1) Total sightings





Number of calves 1 0 0 1 1 0 0 0 1 0


Darwin Harbour (IM) Total sightings





Number of calves 0 0 0 0 2 5 2 1 1 5


Vernon Islands (C2) Total sightings



Number of observations 8 19 - 27 15 19 24 8 9 19

Number of animals 11 27 - 38 19 28 27 11 13 28

Number of calves 1 1 - 2 1 2 0 0 2 2

Maximum group size 2 4 - 4 3 4 2 3 2 4

B1 = 2 replicates; B2, B3, D3 and D4 = 3 replicates; and D2 and D5 = 2 replicates of C2, 3 replicates of C1 and IM.




APPENDIX C SUMMARY OF TURTLE AND DUGONG SIGHTINGS OVERLAID WITH CONFIRMED SEAGRASS HABITAT DURING B1, D2 AND D5 SURVEYS



Appendix C-1 Distribution of dugongs in Darwin Harbour and surrounding areas in May 2012 (B1), May 2013 (D2) and May 2014 (D5), overlaid with mapped seagrass habitat (seagrass data for May 2012, 2013 and 2014, respectively, Geo Oceans 2012, 2013a, 2014)



Appendix C-2 Distribution of turtles in Darwin Harbour and surrounding areas in May 2012 (B1), May 2013 (D2) and May 2014 (D5), overlaid with mapped seagrass habitat (seagrass data for May 2012, 2013 and 2014, respectively, Geo Oceans 2012, 2013a, 2014)




APPENDIX D DUGONG POPULATION SIZE ESTIMATES DURING DREDGING AND BASELINE PHASE SURVEYS



Appendix D Comparison of dugong population size estimates (±SE) during the Baseline Phase (B1 (May 2012), B2 (July 2012) and B3 (October 2012)) and the Dredging Phase (D2 (May 2013), D3 (July 2013), D4 (October 2013) and D5 (May 2014))


Block Month Replicate Estimate ± SE Estimate ± SE

C1

June (B1)

1 238 86 121 87

2 114 40 100 83

3 - - - -

July (B2)

1 - - - -

2 - - - -

3 287 65 424 206

October (B3)

1 81 74 68 35

2 232 149 122 51

3 - - - -

May (D2)

1 - - - -

2 - - - -

3 - - - -

July (D3)

1 - - - -

2 134 58 41 11

3 - - - -

October (D4)

1 - - - -

2 - - - -

3 181 84 62 27

May (D5)

1 187 63 138 34

2 158 56 131 29

3 44 27 13 3

C2

June (B1)

1 252 85 130 71

2 124 45 98 79

3 - - - -

July (B2)

1 - - - -

2 - - - -

3 325 78 273 139

October (B3)

1 99 42 76 30

2 337 103 162 42

3 - - - -

May (D2)

1 - - - -

2 93 45 67 26

3 - - - -

July (D3)

1 - - - -

2 - - - -

3 - - - -



Marsh and Sinclair (1989) Pollock et al. (2006) Block Month Replicate Estimate ± SE Estimate ± SE

October (D4)

1 192 106 126 52

2 327 148 171 76

3 - - - -

May (D4)

1 187 105 159 62

2 455 208 389 141

3 - - - -

IM

June (B1)

1 254 76 128 67

2 232 56 185 121

3 - - - -

July (B2)

1 461 138 223 111

2 361 139 274 180

3 - - - -

October (B2)

1 485 161 434 82

2 364 185 180 56

3 353 207 190 69

May (D2)

1 - - - -

2 - - - -

3 99 48 90 37

July (D3)

1 329 208 176 66

2 225 113 126 50

3 390 246 151 57

October (D4)

1 281 141 164 55

2 446 147 226 66

3 418 212 189 58

May (D5)

1 349 103 313 79

2 120 52 126 48

3 210 76 182 62




APPENDIX E CORRECTED DUGONG DENSITIES DURING DREDGING AND BASELINE PHASE SURVEYS



Appendix E Dugong density (±SE) for blocks C1, C2 and IM during the Baseline Phase (B1 (May 2012), B2 (July 2012) and B3 (October 2012)) and Dredging Phase (D2 (May 2013), D3 (July 2013), D4 (October 2013) and D5 (May 2014)), using the Marsh and Sinclair (1989) and the Pollock et al. (2006) methods and raw sightings data Marsh and Sinclair (1989) Pollock et al. (2006) Raw Block Month Replicate Estimate ± SE Estimate ± SE Month

C1

June (B1)

1 0.3 0.11 0.15 0.11 0.07

2 0.14 0.05 0.13 0.1 0.05

3 - - - - -

July (B2)

1 - - - - 0.01

2 - - - - 0.02

3 0.34 0.08 0.5 0.24 0.11

October (B3)

1 0.1 0.09 0.08 0.04 0.04

2 0.29 0.18 0.15 0.06 0.06

3 - - - - 0.01

May (D2)

1 - - - - 0.01

2 - - - - 0.01

3 - - - - 0.01

July (D3)

1 - - - - 0.06

2 0.2 0.08 0.07 0.02 0.05

3 - - - - 0.03

October (D4)

1 - - - - 0.01

2 - - - - 0.04

3 0.26 0.12 0.09 0.04 0.04

May (D5)

1 0.27 0.09 0.20 0.05 0.06 2 0.23 0.08 0.19 0.04 0.06 3 0.06 0.04 0.02 0.00 0.01

C2

June (B1)

1 0.25 0.08 0.13 0.07 0.06

2 0.12 0.04 0.1 0.08 0.04

3 - - - - -

July (B2)

1 - - - - 0.02

2 - - - - 0.02

3 0.32 0.08 0.27 0.14 0.11

October (B3)

1 0.1 0.04 0.07 0.03 0.04

2 0.33 0.1 0.16 0.04 0.09

3 - - - - 0.02

May (D2)

1 - - - - 0.02

2 0.09 0.04 0.07 0.03 0.04

3 - - - - -

July (D3)

1 - - - - 0.03

2 - - - - 0.02

3 - - - - 0.02

October (D4)

1 0.2 0.11 0.13 0.05 0.06

2 0.34 0.15 0.18 0.08 0.08

3 - - - - 0.01



Marsh and Sinclair (1989) Pollock et al. (2006) Raw Block Month Replicate Estimate ± SE Estimate ± SE Month

May (D5)

1 0.19 0.11 0.16 0.06 0.06 2 0.47 0.21 0.40 0.14 0.14 3 - - - - -

IM

June (B1) 1 0.21 0.06 0.11 0.06 0.05

2 0.19 0.05 0.15 0.1 0.07

July (B2)

1 0.4 0.12 0.19 0.1 0.1

2 0.31 0.12 0.24 0.15 0.08

3 - - - - 0.03

October (B3)

1 0.43 0.14 0.38 0.07 0.17

2 0.32 0.16 0.16 0.05 0.08

3 0.31 0.18 0.17 0.06 0.07

May (D2)

1 - - - - 0.02

2 - - - - 0.02

3 0.09 0.04 0.08 0.03 0.04

July (D3)

1 0.32 0.2 0.19 0.07 0.08

2 0.22 0.11 0.13 0.05 0.05

3 0.38 0.24 0.16 0.06 0.06

October (D4)

1 0.27 0.14 0.16 0.05 0.07

2 0.43 0.14 0.22 0.06 0.09

3 0.4 0.21 0.18 0.06 0.07

May (D5)

1 0.27 0.10 0.30 0.08 0.10 2 0.43 0.05 0.12 0.05 0.02 3 0.40 0.07 0.18 0.06 0.06




APPENDIX F SUMMARY OF TURTLE SIGHTINGS ACROSS DREDGING AND BASELINE PHASE SURVEYS



Appendix F Summary of the number of turtles recorded during Baseline Phase (B1, B2 andB3) and Dredging Phase surveys (D2, D3, D4 and D5) All Areas Total sightings






Bynoe Harbour (C1) Total sightings


Replication number R1 R2 R3 Total Number of observations 99 117 78 294 52 181 266 250 172 183



Darwin Harbour (IM) Total sightings


Replication number R1 R2 R3 Total Number of observations 95 39 51 185 126 200 299 184 161 238



Vernon Islands (C2) Total sightings


Replication number R1 R2 R3 Total Number of observations 129 157 - 286 145 186 338 163 185 354

Number of animals 136 165 - 301 150 192 353 166 195 374

Maximum group size 3 3 - 3 2 2 3 4 4 3 B1 = 2 replicates; B2, B3, D3 and D4 = 3 replicates; and D2 and D5 = 2 replicates of C2, 3 replicates of C1 and IM.




APPENDIX G TURTLE POPULATION SIZE ESTIMATES DURING DREDGING AND BASELINE PHASE SURVEYS



Appendix G Comparison of turtle population size estimates (±SE) during the Baseline Phase (B1 (May 2012), B2 (July 2012) and B3 (October 2012)) and the Dredging Phase (D2 (May 2013), D3 (July 2013), D4 (October 2013) and D5 (May 2014))


C1

June (B1)

1 372 47 399 256

2 297 46 301 197

3 - - - -

July (B2)

1 2291 332 2302 822

2 427 90 428 261

3 1280 132 1260 632

October (B3)

1 877 161 864 154

2 755 179 744 148

3 703 182 690 203

May (D2)

1 517 106 492 140

2 941 144 922 180

3 918 149 931 196

July (D3)

1 653 153 542 152

2 659 162 566 157

3 642 123 542 99

October (D4)

1 834 117 703 156

2 373 71 320 92

3 478 114 387 114

May (D5)

1 705 91 743 128

2 838 132 875 168

3 567 97 689 158

C2

June (B1)

1 1001 151 1113 714

2 579 92 551 333

3 - - - -

July (B2)

1 1380 292 1427 552

2 693 89 695 394

3 587 68 728 427

October (B3)

1 877 116 878 136

2 1059 97 1067 125

3 472 91 481 149

May (D2)

1 488 95 559 133

2 763 153 881 147

3 - - - -

July (D3)

1 374 88 364 60

2 555 116 540 94

3 766 134 720 137

October (D4)

1 685 88 669 115

2 773 117 735 184

3 1017 175 943 199

May (D5)

1 864 103 928 166

2 1162 131 1131 203

3 - - - -




IM

June (B1)

1 698 250 740 475

2 780 92 764 479

3 - - - -

July (B2)

1 2711 607 2770 1044

2 957 149 965 547

3 740 138 576 238

October (B3)

1 1428 143 1420 192

2 513 113 489 105

3 662 112 652 178

May (D2)

1 287 54 315 68

2 391 69 425 98

3 557 89 559 132

July (D3)

1 664 156 613 98

2 642 157 572 90

3 609 152 555 87

October (D4)

1 683 102 625 114

2 539 84 484 87

3 710 101 650 130

May (D5)

1 714 103 695 139

2 290 62 291 50

3 369 53 454 90




APPENDIX H CORRECTED TURTLE DENSITIES DURING DREDGING AND BASELINE PHASE SURVEYS



Appendix H Turtle density (±SE) for blocks C1, C2 and IM during the Baseline Phase (B1 (May 2012), B2 (July 2012) and B3 (October 2012)) and Dredging Phase (D2 (May 2013), D3 (July 2013), D4 (October 2013) and D5 (May 2014)), using the Marsh and Sinclair (1989) and the Pollock et al. (2006) methods and raw sightings data

Marsh and Sinclair (1989) Pollock et al. (2006) Raw Block Month Replicate Estimate ± SE Estimate ± SE

C1

June (B1)

1 0.47 0.06 0.50 0.32 0.23

2 0.37 0.06 0.38 0.25 0.21

3 - - - - -

July (B2)

1 2.70 0.39 2.71 0.97 0.38

2 0.50 0.11 0.50 0.31 0.23

3 1.51 0.16 1.48 0.74 0.73

October (B3)

1 1.08 0.20 1.06 0.19 0.72

2 0.93 0.22 0.92 0.18 0.73

3 0.87 0.22 0.85 0.25 0.57

May (D2)

1 0.64 0.13 0.61 0.17 0.40

2 1.16 0.18 1.14 0.22 0.78

3 1.13 0.18 1.15 0.24 0.77

July (D3)

1 0.95 0.22 0.79 0.22 0.42

2 0.96 0.24 0.82 0.23 0.42

3 0.93 0.18 0.79 0.14 0.41

October (D4)

1 1.21 0.17 1.02 0.23 0.67

2 0.54 0.10 0.47 0.13 0.31

3 0.70 0.17 0.56 0.17 0.38

May (D5)

1 1.03 0.13 1.08 0.19 0.78

2 1.22 0.19 1.27 0.24 0.92

3 0.83 0.14 1.00 0.23 0.70

C2

June (B1)

1 0.98 0.15 1.09 0.70 0.47

2 0.56 0.09 0.54 0.32 0.33

3 - - - - -

July (B2)

1 1.35 0.28 1.39 0.54 0.26

2 0.68 0.09 0.68 0.38 0.32

3 0.57 0.07 0.71 0.42 0.40

October (B3)

1 0.86 0.11 0.86 0.13 0.61

2 1.04 0.10 1.05 0.12 0.85

3 0.46 0.09 0.47 0.15 0.34

May (D2)

1 0.48 0.09 0.55 0.13 0.31

2 0.75 0.15 0.86 0.14 0.53

3 - - - - -

July (D3)

1 0.38 0.09 0.37 0.06 0.23

2 0.57 0.12 0.55 0.10 0.32

3 0.78 0.14 0.74 0.14 0.44

October (D4)

1 0.70 0.09 0.69 0.12 0.54

2 0.79 0.12 0.75 0.19 0.59

3 1.04 0.18 0.97 0.20 0.77



Marsh and Sinclair (1989) Pollock et al. (2006) Raw Block Month Replicate Estimate ± SE Estimate ± SE

May (D5)

1 0.89 0.11 0.95 0.17 0.70

2 1.19 0.13 1.16 0.21 0.85

3 - - - - -

IM

June (B1)

1 0.58 0.21 0.61 0.39 0.27

2 0.64 0.08 0.63 0.40 0.36

3 - - - - -

July (B2)

1 2.33 0.52 2.38 0.90 0.36

2 0.82 0.13 0.83 0.83 0.39

3 0.64 0.12 0.49 0.28 0.25

October (B3)

1 1.25 0.13 1.25 0.17 0.88

2 0.45 0.10 0.43 0.09 0.39

3 0.58 0.10 0.57 0.16 0.42

May (D2)

1 0.25 0.05 0.28 0.06 0.21

2 0.34 0.06 0.37 0.09 0.30

3 0.49 0.08 0.49 0.12 0.40

July (D3)

1 0.64 0.15 0.59 0.09 0.24

2 0.62 0.15 0.55 0.09 0.26

3 0.59 0.15 0.54 0.08 0.27

October (D4)

1 0.66 0.10 0.60 0.11 0.43

2 0.52 0.08 0.47 0.08 0.33

3 0.69 0.10 0.63 0.13 0.44

May (D5)

1 0.69 0.10 0.67 0.13 0.47

2 0.28 0.06 0.28 0.05 0.20

3 0.36 0.05 0.44 0.09 0.26




APPENDIX I TURTLE SUB-BLOCK POPULATION SIZE ESTIMATES DURING D5 AERIAL SURVEYS



Appendix I Turtle sub-block population size estimates (± SE) in: C1, IM and C2 during D5 (May 2014) Block Sub-block Replicate Sightings in

Transect Marsh & Sinclair (1989) Pollock et al. (2006)

Estimate ±SE Estimate ±SE

C1

1

1 2 24 6 15 3

2 3 30 9 17 4

3 2 58 0 11 3

Average 2 37 13 15 4

2

1 69 58 88 604 118

2 78 584 108 620 121

3 63 542 107 589 119

Average 70 395 245 604 106

3

1 15 172 40 124 25

2 23 237 89 158 33

3 10 161 33 76 15

Average 16 190 65 119 36

4

1 13 123 42 94 19

2 13 136 70 102 20

3 3 57 29 19 4

Average 10 105 55 72 32

IM

1

1 9 96 16 71 13

2 14 99 17 205 37

3 9 71 17 61 14

Average 11 89 17 112 65

2

1 9 99 26 74 13

2 2 81 42 33 6

3 5 103 38 65 11

Average 5 94 32 57 19

3

1 24 191 63 185 36

2 8 77 28 119 6

3 11 88 28 65 11

Average 14 119 64 123 46

4

1 21 172 40 185 36

2 10 134 20 119 23

3 11 107 19 104 20

Average 14 138 35 136 41

5

1 21 156 28 43 30

2 4 49 18 139 27

3 13 131 35 123 24

Average 13 112 50 102 48

6

1 11 78 14 162 33

2 1 23 0 56 11

3 2 24 3 90 18

Average 5 42 26 103 48



Block Sub-block Replicate Sightings in Transect Marsh & Sinclair (1989) Pollock et al. (2006)


C2

1

1 14 148 43 96 19

2 20 188 42 139 27

3 - - - - -

Average 17 168 31 117 20

2

1 46 282 55 347 70

2 62 432 55 417 89

3 - - - - -

Average 54 357 62 382 55

3

1 50 344 56 353 70

2 59 447 86 425 89

3 - - - - -

Average 55 396 55 389 56

4

1 19 173 46 130 25

2 16 225 52 120 24

3 - - - - -

Average 18 199 36 125 17




APPENDIX J CORRECTED TURTLE SUB-BLOCK DENSITIES DURING D4 AERIAL SURVEYS



Appendix J Turtle sub-block corrected densities within: C1, IM and C2 during D5 (May 2014)

Block Sub-Block Replicate Area

(km2) Sightings in

Transect Marsh & Sinclair (1989) Pollock et al. (2006)


C1

1 1

94.7 2 0.25 0.06 0.16 0.03

2 3 0.32 0.10 0.18 0.04

3 2 0.61 0.00 0.12 0.03

2 1

296.4 69 0.20 0.30 2.04 0.40

2 78 1.97 0.36 2.09 0.41

3 63 1.83 0.36 1.99 0.40

3 1

150.2 15 1.15 0.27 0.83 0.17

2 23 1.58 0.59 1.05 0.22

3 10 1.07 0.22 0.50 0.10

4

1

145.8 13 0.84 0.29 0.64 0.13

2 13 0.93 0.48 0.70 0.14 3 3 0.39 0.20 0.13 0.03

IM

1

1

193.8 9 0.50 0.08 0.37 0.07

2 14 0.51 0.09 1.06 0.19 3 9 0.37 0.09 0.31 0.07

2

1

128.7 9 0.77 0.20 0.57 0.10

2 2 0.63 0.33 0.26 0.05 3 5 0.80 0.30 0.50 0.09

3

1

121.5 24 1.57 0.52 1.53 0.30

2 8 0.63 0.23 0.98 0.05 3 11 0.72 0.23 0.53 0.09

4

1

171.5 21 1.00 0.23 1.08 0.21

2 10 0.78 0.12 0.69 0.14 3 11 0.62 0.11 0.61 0.12

5

1

85.9 21 1.82 0.33 0.50 0.35

2 4 0.57 0.21 1.61 0.31 3 13 1.53 0.41 1.44 0.28

6

1

333.1 11 0.23 0.04 0.49 0.10

2 1 0.07 0.00 0.17 0.03 3 2 0.07 0.01 0.27 0.05

C2

1

1

224.5 14 0.66 0.19 0.43 0.08

2 20 0.84 0.19 0.62 0.12 3 - - - - -

2

1

207.1 46 2.09 0.27 2.01 0.43

2 62 2.09 0.27 1.84 0.27 3 - - - - -

3

1

393.6 50 0.87 0.14 0.99 0.14

2 59 0.44 0.12 0.33 0.06 3 - - - - -

4

1

150.7 19 1.15 0.31 0.86 0.17

2 16 1.49 0.35 0.80 0.16

3 - - - - -




APPENDIX K LAND SURVEY DATA DURING D5 SURVEY



Appendix K Land-based observations at Channel Island and Cullen Bay during D5 surveys in May 2014

Location Replicate Date: Observer Positions (lat.)

Observer Positions (long.)

Direction observed: Time Animal type Age Class Bearing from

observer (degrees) Est. Distance from

observer

Channel Island Rep 1 14-May-14 12°33.242'S 130°52.419'E S 9:37:00 Green Turtle Juvenile 260 40


Channel Island Rep 1 14-May-14 12°33.242'S 130°52.419'E S 11:30:00 Unidentified Turtle Unknown 250 50


Channel Island Rep 1 14-May-14 12°33.242'S 130°52.419'E S 11:37:00 Green Turtle Adult 115 80

Channel Island Rep 1 14-May-14 12°33.242'S 130°52.419'E S 11:44:00 Green Turtle Unknown 140 30

Channel Island Rep 1 14-May-14 12°33.242'S 130°52.419'E S 11:53:00 Unidentified Turtle Juvenile 230 25





Channel Island Rep 1 14-May-14 12°33.242'S 130°52.419'E N 9:59:00 Green Turtle Juvenile 235 20


Channel Island Rep 1 14-May-14 12°33.242'S 130°52.419'E N 10:13:00 Green Turtle Juvenile/sub-adult 294 20

Channel Island Rep 1 14-May-14 12°33.242'S 130°52.419'E N 10:22:00 Unidentified Turtle Juvenile 295 80


Channel Island Rep 1 14-May-14 12°33.242'S 130°52.419'E N 10:55:00 Unidentified Turtle Unknown 315 80







Channel Island Rep 1 14-May-14 12°33.242'S 130°52.419'E N 11:26:00 Green Turtle Juvenile unknown 50


Channel Island Rep 1 14-May-14 12°33.242'S 130°52.419'E N 11:26:00 Green Turtle Unknown 319 50

Channel Island Rep 1 14-May-14 12°33.242'S 130°52.419'E N 11:26:00 Green Turtle Unknown 294 80

Channel Island Rep 1 14-May-14 12°33.242'S 130°52.419'E N 11:32:00 Green Turtle Adult 336 50



Channel Island Rep 1 14-May-14 12°33.242'S 130°52.419'E N 11:37:00 Green Turtle Adult 342 50









Location Replicate Date: Observer Positions (lat.)

Observer Positions (long.)

Direction observed: Time Animal type Age Class Bearing from

observer (degrees) Est. Distance from

observer

Channel Island Rep 1 14-May-14 12°33.242'S 130°52.419'E N 12:45:00 Unidentified Turtle Adult 306 30







Channel Island Rep 2 16-May-14 12°33.242'S 130°52.419'E N 12:02:00 Unidentified Turtle unknown 343 250




Channel Island Rep 2 16-May-14 12°33.242'S 130°52.419'E S 12:57:00 Green turtle Juvenile 243 30

Cullen Bay Rep 1 14-May-14 12°26.849'S 130°49.404'E NE 7:33:00 Dugong Large juvenile 13 50

Cullen Bay Rep 1 14-May-14 12°26.849'S 130°49.404'E NE 10:28:00 Bottlenose Dolphin Adult 342 55

Cullen Bay Rep 1 14-May-14 12°26.849'S 130°49.404'E NE 10:30:00 Bottlenose Dolphin Adult 310 250

Cullen Bay Rep 2 16-May-14 12°26.849'S 130°49.404'E NE 7:53:00 Dugong unknown 32 50

Cullen Bay Rep 2 16-May-14 12°26.849'S 130°49.404'E NE 9:00:00 Bottlenose dolphin unknown 350 250+

Cullen Bay Rep 2 16-May-14 12°26.849'S 130°49.404'E NE 9:04:00 Bottlenose dolphin unknown 23 250+

Cullen Bay Rep 2 16-May-14 12°26.849'S 130°49.404'E NE 11:20:00 Bottlenose dolphin unknown 30 150




Cullen Bay Rep 2 16-May-14 12°26.849'S 130°49.404'E W 8:32:00 Dugong adult 312 150

Cullen Bay Rep 2 16-May-14 12°26.849'S 130°49.404'E W 8:56:00 Unidentified dolphin adult 312 200




APPENDIX L REHABILITATED TURTLE SUMMARY DATA



Appendix L Details of turtle rehabilitation as of June 2014 ID No.

Date of Stranding

Turtle Species and Life Stage

General location of Stranding Injuries Rehab details Release details Comments

Approximate rehab time (months)

Proposed release location Suitability for tagging Release details Release date

1 July 2011 Olive Ridley (juvenile) Bare Sand Island

Hatchling severely dehydrated and weakened. Taken to Territory Wildlife Park for recovery

22 months Bynoe Harbour- Bare Sand Island

Unsuitable for TDMP- targeted species include Hawksbill and Green Turtles

Released- satellite tagged by Kiki Dethmers, Arafura Timor Research Facility, NAMRA, May 2013

May 2013 "Oliver" - as of Sept 2013, tracks still being transmitted, data on Seaturtle.org

2 July 2011 Flatback (juvenile) Bare Sand Island

Hatchling severely dehydrated and weakened. Taken to Territory Wildlife Park for recovery

22 months Bynoe Harbour- Bare Sand Island

Unsuitable for TDMP- targeted species include Hawksbill and Green Turtles

Released- satellite tagged by Kiki Dethmers, Arafura Research Station, CDU, May 2013

May 2013 "Henderson" - as of Sept 2013, tracks still being transmitted, data on Seaturtle.org

3 September 2012

Flatback (adult) Darwin Harbour Boat strike injury – mid

carapace damage 6 months NA

Unsuitable for TDMP due to boat strike injury (position needed for harness and transmitter) – flipper tagged attached by Kiki

Released - Ray Chatto (DLRM) February 2013

Turtle measurements: 56.8cm long, 48.9cm wide & weighs 20kg; the plastron length is 55.5 cm & width is 54.8cm. Boat strike injury left a significant area of scar tissue on the turtle’s carapace. The turtle was not able to carry a harness due to the injury. Released without satellite tag, flipper tagged by Ray Chatto on release in February 2013

4 October 2012

Flatback (adult female)

East of Hotham Point (~70 km from Darwin)

Floater 1 month Lee Point Unsuitable for TDMP, but released by Kiki

Released - Kiki Dethmers, Arafura Timor Research Facility, NAMRA, - satellite transmitter attached & flipper tagged at Lee Point

7 December 2012

Turtle measured on captured by TD team in early Oct 2012, 81.9cm long (CCL), 67cm wide (CCW), weight 67kg; "Michala" - tracks transmitted for 2 months, data on Seaturtle.org

5 October 2012

Flatback (juvenile)

Pioneer Beach, Bynoe Harbour Floater (no other injuries) Unknown Unknown Unknown

6 unknown Green (unknown)

Found at Mandorah Beach, Darwin Harbour

Boat strike injury – severe head and carapace damage

unknown unknown unknown Unknown Unknown Unknown

7 May 2013 Flatback (adult male) Near Charles Point Possible boat strike,

carapace damage 1.5 months Nightcliff jetty Unsuitable for TDMP- targeted species include Hawksbill and Green Turtles

Released- satellite tagged by Kiki Dethmers, Arafura Timor Research Facility, NAMRA, May 2013

May 2013 "Charlie" - as of Sept 2013, trackes still being transmitted, data on Seaturtle.org

8 May 2013 Hawksbill (juvenile) Darwin Harbour Head injury 3 - 4 months To be determined

Unsuitable for TDMP-the turtle was found outside of the project area

will be released in late 2013, not suitable for TDMP

August/September 2013

Still in rehab (as of Sept 2013), update from Stephen Cutter (21 Aug) - head injuires appear to have subsided- the turtle will be flipper tagged and released

9 May 2013 Hawksbill (juvenile) Darwin Harbour Darwin Harbour Unsuitable- missing fore flipper Released without tag by

Ray Chatto, May 2013 May 2013

10 July 2013 Flatback (juvenile) Darwin Harbour Floater? Boat strike unknown unknown Unsuitable for TDMP – targeted species include Hawksbill and Green Turtles

will be released in late 2013, not suitable for TDMP

TBC housed at CDU - update from SC (21 Aug) - will be released late 2013 and tagged by Kiki Dethmers

11 October 2013

Green (unknown) Bynoe Harbour 46 kg Floater, very

dehydrated, very sunken died overnight nil nil (past away) nil (past away) nil NPWS picked up turtle 30/10

12 March 2014 Green (male adult?) Casuarina Beach

Prop wound to the rear right quarter of his shell, partially penetrating intramuscular and a severe gash diagonally down the upper side of his tail

86kg unknown, but good chance of recovery

Casuarina Beach unknown at this stage

Marine Wildwatch Id Number = 2014_453 Danny Low Choy (Marine Wildwatch Officer)



ID No.

Date of Stranding

Turtle Species and Life Stage

General location of Stranding Injuries Rehab details Release details Comments

Approximate rehab time (months)

Proposed release location Suitability for tagging Release details Release date

13 March 2014 Hawksbill (adult female – Linh)

Evans Shoal (250 km north of Darwin)

No severe injuries except for shallow puncture wound (potentially from a spear) on top right hand side of the carapace.

10 days rehabilitation Nightcliff Jetty

Satellite and flipper tagged. Not included as part of TDMP as it was located outside of project area.

Released with satellite tag by Rachael Groom from DLRM from Nightcliff Jetty, Darwin.

27 March 2014

After much discussion, it was decided 'Linh' should be released locally instead of travelling 36 hours to the initial point of capture 250kms north of Darwin between Evans Shoal and Kupang. Linh was released at Nightcliff Jetty and the tag continues to transmit data.

turtle and dugong monitoring end of dredging report · turtle and dugong monitoring end of dredging...

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