gvi seychelles marine report jan - jun 2013 (cap ternay).pdf
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GVI Seychelles Cap Ternay Marine Expedition Scientific Report January - June 2013TRANSCRIPT
Global Vision International, Seychelles - Mahé Report Series No. 131
ISSN 1751-2255 (Print)
GVI Seychelles – Mahé
Marine Conservation Expedition
January - June 2013
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GVI Seychelles – Mahé/Marine Conservation Expedition Report January - June 2013
Submitted in whole to Global Vision International
Seychelles National Parks Authority (SNPA)
Produced by
Lee Cassidy – Science Coordinator
Sam Howlett– Science Coordinator
And
Christophe Mason-Parker Country Director Charlotte Broadhead Scholar
Emily Allen Base Manager Jordon Bonnett Scholar
Kate Poss Community Leader Carly Reeves Scholar
Joe Daniels Dive Officer Jessica Skippen Scholar
Lee Bush Dive Officer
Thank you also to our hardworking volunteers for the collection of all data;
Mary Brown, Bill Bawden, George Hazeldine, FabienneJoos, Billy Rich, Eden Yeandle, Jessica
Skippen, Victoria Beasley, Janis Pizics, James Clack, James Mckenzie, Clare Walkden, Lauren Hall,
Kais Khoury, MajaLofqvist, Melanie Knabel, Denise Renninger, Rolf Engels, Johan Molgard
Sorenson, MichealTejellsen, Charlotte Orba, Alex Wilson, Carl Baden, Charlotte Abraham,
SebasteinWesterholm, BogdanMihalceaEliade, Andrew Leach, Marion Heyer, Shawn Middleton,
Rachel Duczynski, Matthew Waller, PhillippaSturges, Bradley Knight, JayeBransgrove, CharlieDorey,
Carl-Johann Renner, Beth Stuart, Kyle Thomas, Gaius Timms, Jennifer Laurence, Silvia Helfenstien,
Hannah Wolstenholm, Ashleigh McNie, Gabi Rudolf, Christopher Connell, Susanne JafariChamgavi,
Thomas Kitchen, Rory Langman, Sarah Taylor, Lewis Plush, Philipp Ding, Charlotte Hilton,
StanislavShub& Florian Klein.
GVI Seychelles – Mahé/Marine Conservation Expedition
Address: GVI c/o SNPA, PO Box 1240, Victoria, Mahé, Seychelles
Email: [email protected] Web page: http://www.gvi.co.uk and http://www.gviusa.com
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Abstract
This report summaries the findings from surveys conducted between January to June 2013
which examined coverage of all epibenthic organisms, along with scleractinian coral
diversity, in addition to density of both reef and commercial fish species and the abundance
of key indicator invertebrate species. Results were then combined with previous survey data
from the program to assess and analyse trends and changes in the coral reef communities
along the North-West coastline of Mahé.
Analysis of the surveys focussing on the epibenthic communities show that overall coral
cover has increased to 37.64% (± 1.94); the highest coverage seen yet in the monitoring
program.Granitic sites increased by 2.67% in 2013 whilst carbonate reefs remained stable
from 2012. Analysis of the structural complexity shows that branching coral coverage
increased again this year maintaining its dominance from 2011.This continued increase in
the growth of the physical matrix of the reefs is a very positive sign for the future of these
reefs being able to support a wider diversity of life.
Fish results show that the overall density of fish on survey sites has changed very little over
the last couple of years, with changes mainly to the community composition. Corallivores
continue to increase; coral cover and corallivores density were correlated (R2 =0.926),
highlighting the importance of live coral cover for specialist species. Protected areas showed
higher density and diversity of fish species, highlighting again the need to maintain correct
management of these critical areas.
Abundance of invertebrate species has increased since the initial surveys conducted in
2005. Results from 2013 however show a decrease in most of the invertebrate phyla. The
most significant decrease for 2013 was seen in the Mollusca and Arthropoda phyla. Further
analysis of species abundance within these phyla showed that the decrease in mean
abundance was mainly due to a drop in Oyster numbers at granitic sites for Mollusc's and
crab species on carbonate reefs for the Arthropoda phylum. Indicating that these are issues
effecting specific species on specific substrate types, as opposed to larger scale problems
effecting overall phyla numbers in the survey area.
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Contents 1 Introduction ..................................................................................................................... 8
1.1 Survey Sites ............................................................................................................ 10
2 Aims .............................................................................................................................. 11
2.1 Species Lists ........................................................................................................... 11
2.1.1 Coral ................................................................................................................. 11
2.1.2 Fish ................................................................................................................... 11
2.1.3 Invertebrates .................................................................................................... 12
2.2 Training .................................................................................................................... 12
2.2.1 Dive Training .................................................................................................... 12
2.2.2 Species Identification ....................................................................................... 12
2.2.3 Survey Methodology ......................................................................................... 13
3. Methodology ................................................................................................................. 13
3.1. Coral ........................................................................................................................ 13
3.1.1. Line Intercept Transects (LIT) .......................................................................... 13
3.1.2 Coral Diversity Belt Transects .......................................................................... 14
3.2 Fish .......................................................................................................................... 14
3.2.1 Stationary Point Count ..................................................................................... 14
3.2.2 50m Belt Transects .......................................................................................... 15
3.3 Invertebrates ............................................................................................................ 15
3.3.1 10m Belt Transect ............................................................................................ 15
3.3.2 50m Belt Transect ............................................................................................ 15
3.4 Environmental Parameters ...................................................................................... 17
4. Results .......................................................................................................................... 18
4.1. Surveys Completed ................................................................................................. 18
4.2. Percentage mean live hard coral cover ................................................................... 18
4.3. Benthic Assemblage ................................................................................................ 19
4.4. Structural Complexity .............................................................................................. 22
4.5 Coral Diversity ......................................................................................................... 24
4.6 Overall Fish Results ................................................................................................ 25
4.7 Combined Fish Density 2005 – 2013 ...................................................................... 25
4.8 Fish Densities with regards to Feeding Guilds ........................................................ 27
4.9 Influence of Marine Protected Areas on Fish Densities 2005 – 2013 ..................... 29
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4.10 Fish Species Diversity ............................................................................................. 31
4.11 Commercial Fish Sizing Results .............................................................................. 32
4.12 Invertebrate Densities from 10m Transects ............................................................. 33
4.13 Invertebrate Densities from 50m Belts .................................................................... 35
4.14 Sea Cucumber Densities ......................................................................................... 37
5 Discussion .................................................................................................................... 38
5.1 Coral Surveys .......................................................................................................... 38
5.2 Fish Surveys ............................................................................................................ 41
5.3 Invertebrate Surveys ............................................................................................... 44
6 Additional Ecosystem Monitoring .................................................................................. 45
6.1. Turtles ...................................................................................................................... 45
6.1.1. Incidental Turtle Sightings ................................................................................ 45
6.1.2. Beach Patrols for Nesting Turtles ..................................................................... 47
6.1.3. In-water Surveys of Turtle Behaviour ............................................................... 47
6.1.4. Photo Identification of Turtles ........................................................................... 49
6.2. Crown of Thorns ...................................................................................................... 50
6.3. Cetacean Sightings ................................................................................................. 50
6.4. Whale Shark Sightings ............................................................................................ 50
6.5. Plankton Sampling ................................................................................................... 51
7. Non-survey Programmes .............................................................................................. 52
7.1 Extra Programmes ................................................................................................... 52
7.1.1 Internships ........................................................................................................ 52
7.2 Community Development ........................................................................................ 52
7.2.1 Community Education Programmes ................................................................. 52
7.2.2 GVI Charitable Trust ......................................................................................... 52
7.2.3 National Scholarship Programme ..................................................................... 53
8. References ................................................................................................................... 54 9. Appendices ................................................................................................................... 56
Appendix A. Details of sites surveyed by GVI Seychelles – Mahé, year round. Sites in
bold-type text are located within Marine Protected Areas. ................................................. 56
Appendix B. Scleractinian coral genera surveyed by GVI Seychelles - Mahé. .................. 57
Appendix C. Fish families, genera and species surveyed by GVI Seychelles - Mahé. ...... 58
Appendix D. Fish feeding guilds analysed by GVI Seychelles – Mahé. ............................. 61
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Appendix E. Fish species lists divided into commercial and reef species analysed by GVI
Seychelles – Mahé. ............................................................................................................ 62
Appendix F. List of invertebrate species surveyed on 50m belt transects by GVI
Seychelles – Mahé. ............................................................................................................ 63
Appendix G. Invertebrates surveyed on 10m LIT transects by GVI Seychelles – Mahé. ... 64
Figures List
FIGURE 1.1 LOCATION AND SUBSTRATE TYPE OF GVI SURVEY SITES. ...................................................................................... 10
FIGURE 3. 1 LAYOUT OF CORAL LIT AND DIVERSITY BELTS AT EACH SURVEY SITE, WHERE THE SHORELINE IS REPRESENTED
BY THE TOP OF THE FIGURE AND THE DISTANCE FROM SHORE INDICATES INCREASING DEPTH. ................................. 16
FIGURE 3.2. LAYOUT OF FISH SPC AND BELTS, AND 50M INVERTEBRATE TRANSECTS AT EACH SURVEY SITE, WHERE THE
SHORELINE IS REPRESENTED BY THE TOP OF THE FIGURE AND THE DISTANCE FROM SHORE INDICATES INCREASING
DEPTH. ............................................................................................................................................................................ 16
FIGURE 4. 1 MEAN PERCENTAGE CORAL COVER (± SE) AT THE CARBONATE AND THE GRANITIC SITES, FOR EACH SURVEY
PERIOD FROM 2005 TO 2013 .......................................................................................................................................... 19
FIGURE 4. 2 MEAN PERCENTAGE COVERAGE FOR CORAL, ALGAE, OTHER BENTHIC ORGANISMS AND BARE SUBSTRATE
FROM ALL SITES FOR JAN – JUN 2013 ............................................................................................................................. 19
FIGURE 4. 3 LARGE SCALE SPATIAL DISTRIBUTION OF PERCENTAGE COVERAGE OF CORAL, ALGAE, VARIOUS BENTHIC
ORGANISMS AND BARE SUBSTRATE ACROSS ALL SITES, RUNNING EAST TO WEST ACROSS NORTH WEST MAHÉ FROM
2013 ................................................................................................................................................................................ 20
FIGURE 4. 4 MEAN PERCENTAGE COVERAGE OF ALGAE AND BENTHIC ORGANISMS ON SURVEYED CARBONATE REEFS FROM
2005 – 2013. ................................................................................................................................................................... 21
FIGURE 4. 5 MEAN PERCENTAGE COVERAGE OF ALGAE AND BENTHIC ORGANISMS ON SURVEYED GRANITIC REEFS FROM
2005 – 2013. ................................................................................................................................................................... 22
FIGURE 4. 6 PERCENTAGE COVERAGE OF HARD CORAL FOUND ACROSS ALL REEFS FURTHER DIVIDED BY CORAL LIFEFORM
PREVALENCE FROM 2005 -‐ 2013 .................................................................................................................................... 22
FIGURE 4. 7 PERCENTAGE COVERAGE OF CORAL LIFEFORM FOUND ACROSS ALL REEFS FROM 2005 – 2013 ........................ 23
FIGURE 4. 8 PERCENTAGE OF CORAL LIFE FORMS ON CARBONATE SITES 2005 – 2013 ........................................................... 23
FIGURE 4. 9 PERCENTAGE OF CORAL LIFE FORM ON GRANITIC SITES FROM 2005 – 2013 ...................................................... 24
FIGURE 4. 10 COMPARISON OF MEAN CORAL GENERA RICHNESS (± SE) FOR CARBONATE AND GRANITIC SITES FROM 2005 –
2013. ............................................................................................................................................................................... 24
FIGURE 4. 11 MEAN DENSITY PER M² OF ALL SURVEYED FISH SPECIES ACROSS ALL SURVEY SITES, 2005 -‐ 2013. .................. 26
FIGURE 4. 12 A COMPARISON OF MEAN DENSITY PER M² OF ALL SURVEYED FISH SPECIES BETWEEN CARBONATE AND
GRANITIC SUBSTRATE SITES, 2005 – 2013 ...................................................................................................................... 26
FIGURE 4. 13 COMPARISON OF FISH FEEDING GUILDS THROUGH DENSITY PER M² ACROSS ALL SITES, 2005 – 2013. ........... 27
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FIGURE 4. 14 COMPARISON OF FEEDING GUILDS THROUGH DENSITY PER M² ACROSS ALL SITES, 2005 – 2013,
DISREGARDING HERBIVORES. ......................................................................................................................................... 28
FIGURE 4. 15 COMPARISON OF LINEAR TREND LINES FOR CORAL COVER AND CORALLIVORE DENSITY ACROSS ALL SITES
FROM 2004 TO PRESENT. ................................................................................................................................................ 28
FIGURE 4. 16 MEAN CORAL COVER AGAINST CORALLIVORE DENSITY FOR ALL SITES FROM 2005 TO PRESENT. .................... 29
FIGURE 4. 17 OVERALL MEAN DENSITY PER M OF FISH INSIDE AND OUTSIDE MARINE PROTECTED AREAS, NOV-‐DEC 2005 TO
JAN-‐JUN 2013. ................................................................................................................................................................. 29
FIGURE 4. 18 MEAN DENSITY OF FISH PER M² ON CARBONATE SUBSTRATE SITES INSIDE AND OUTSIDE MARINE PROTECTED
AREAS, NOV-‐DEC 2005 TO JAN-‐JUN 2013. ...................................................................................................................... 30
FIGURE 4. 19 MEAN DENSITY OF FISH PER M ON GRANITIC SUBSTRATE SITES INSIDE AND OUTSIDE MARINE PROTECTED
AREAS, NOV-‐DEC 2005 TO JAN-‐JUN 2013. ...................................................................................................................... 30
FIGURE 4. 20 SPECIES-‐RICHNESS (NUMBER OF FISH SPECIES FOUND) ACROSS ALL SURVEY SITES ALONG NW MAHÉ, 2013.
GREEN DENOTES SITES WITHIN MARINE PROTECTED AREAS AND BLUE DENOTES NON-‐PROTECTED SITES. ................ 31
FIGURE 4. 21 A COMPARISON OF SPECIES-‐RICHNESS (NUMBER OF FISH SPECIES) BETWEEN THE SAME SITES OF NW MAHÉ
IN 2005 AND IN 2013. ..................................................................................................................................................... 32
FIGURE 4. 22 MEAN DENSITY (INDIVIDUALS PER M²) OF INVERTEBRATE PHYLA AND BLACK SPINED SEA URCHINS AT
CARBONATE REEF SITES, FOR EVERY SURVEY PERIOD FROM 2005 TO 2013 .................................................................. 33
FIGURE 4. 23 MEAN DENSITY (INDIVIDUALS PER M²) OF INVERTEBRATE PHYLA AND BLACK SPINED SEA URCHINS AT
GRANITIC REEF SITES, FOR EVERY SURVEY PERIOD FROM 2005 TO 2013. ..................................................................... 34
FIGURE 4. 24 MEAN DENSITY (INDIVIDUALS PER M²) OF INVERTEBRATE PHYLA AND BLACK SPINED SEA URCHINS AT
CARBONATE REEF SITES, FOR EVERY SURVEY PERIOD FROM 2005 TO 2013. ................................................................. 34
FIGURE 4. 25 MEAN DENSITY PER M2 OF ALL SURVEYED INVERTEBRATE SPECIES ACROSS NORTH-‐WEST MAHÉ, 2013. ........ 35
FIGURE 4. 26 MEAN DENSITY PER M2 OF ALL SURVEYED INVERTEBRATE SPECIES ACROSS NORTH-‐WEST MAHÉ FROM 2009 -‐
2013. ............................................................................................................................................................................... 36
FIGURE 4. 27 MEAN DENSITY PER M2 OF CUSHION SEASTAR (CULCITA SPP.), CROWN OF THORNS (ACANTHASTERPLANCI)
AND THE GASTROPODS DRUPELLA SP. FROM 2009 -‐ 2013 ACROSS ALL SITES. .............................................................. 36
FIGURE 4. 28 MEAN NUMBER OF SEA CUCUMBERS RECORDED PER SITE FROM 2006 -‐ 2013. ............................................... 37
FIGURE 4. 29 DENSITY PER M2 OF INDIVIDUAL SEA CUCUMBER SPECIES ACROSS ALL SURVEY SITES OF NORTH-‐WEST MAHÉ
FROM 2008 -‐ 2013. ......................................................................................................................................................... 37
FIGURE 6. 1 FREQUENCY (%) OF HAWKSBILL AND GREEN TURTLE SIGHTINGS AROUND NORTH-‐WEST MAHÉ FROM OCT-‐ DEC
2005 TO APRIL-‐JUN 2013. ............................................................................................................................................... 46
FIGURE 6. 2 MEAN CARAPACE LENGTH OF HAWKSBILL TURTLES AROUND NORTH-‐WEST MAHÉ FROM JAN-‐ MAR 2006 TO
APR-‐ JUN 2013 ................................................................................................................................................................ 47
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1 Introduction
Global Vision International (GVI) Seychelles comprises of two expeditions based on the
granitic inner islands of Seychelles. One on Mahé, the largest and most heavily populated
island in the Seychelles group, located at the Cap Ternay Research Centre in Baie Ternay
National Park and one on Curieuse Island within the Curieuse national marine park, located
north of Praslin. The marine parks at which both GVI bases are located are controlled and
managed by the Seychelles National Parks Authority (SNPA). All of GVI’s scientific work in
the Seychelles is carried out on behalf of our local partners and at their request, using their
methodology; GVI supplies experienced staff, trained volunteers and equipment to conduct
research in support of their on-going work. GVI’s key partner is the conservation and
research section, which is the research arm of SNPA. Additional local partners include the
Marine Conservation Society Seychelles (MCSS) and the Seychelles Fishing Authority
(SFA).
Seychelles National Parks Authority (SNPA): A local organisation partly funded by the
government, encompassing the conservation and research section and the Marine Parks
Authority (MPA). These organisations have the respective aims of carrying out marine
research in the Seychelles and of managing and patrolling the marine parks. The coral and
fish monitoring carried out for SNPA constitutes the majority of the work conducted by the
volunteers.
Marine Conservation Society Seychelles (MCSS): A local non-governmental organisation
(NGO) that carries out environmental research in the Seychelles, currently monitoring whale
sharks, cetaceans and turtles around Mahé. GVI assists with all three of these research
programmes by documenting the presence or absence of turtles on every dive throughout
the phase, conducting in-water turtle behaviour survey dives and also turtle nesting surveys.
Along with the turtle work GVI reports incidental sightings of cetaceans and whale sharks
and undertakes weekly plankton sampling to aid with year round monitoring of plankton
levels in conjunction with the arrival of whale sharks to Mahé Island.
Seychelles Fishing Authority (SFA): The governing body, which oversees the management
and regulation of commercial and artisanal fisheries in the Seychelles. This government
agency is directly concerned with setting the catch, bag and seasonal limits that apply to
local stocks on an annual basis, as well as managing the international export industry that is
generated from the harvest of fisheries across the Seychelles Exclusive Economic Zone
(EEZ).
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In 1998, a worldwide coral bleaching event decimated much of the coral surrounding the
inner granitic islands of the Seychelles, with hard coral mortality reaching 95% in some
areas (Spencer et al. 2000). It is thought that this was caused by the high ocean temperatures
associated with an El Nino Southern Oscillation event at that time. Efforts to monitor the
regeneration of reefs in the Seychelles were initiated as part of the Shoals of Capricorn, a
three year programme started in 1998 and funded by the Royal Geographic Society in
conjunction with the Royal Society. Theresearch and conservation section of the SNPA was
set up by the Shoals of Capricorn in an effort to ensure continuation of the work started, as
well as to assist the Marine Parks Authority (MPA) with the management of the existing
marine parks. The predominant objective for the Seychelles GVI expedition is to aid this
monitoring programme and thereby assist in the construction of management plans that will
benefit the future recovery of coral reefs in the area.
Between 2000 and the beginning of the GVI expedition in 2004 the Seychelles marine
ecosystem management program (SEYMEMP) took place, this was the most comprehensive
assessment of the coral reefs within the inner islands of the Seychelles to date. Eighty one
carbonate and granitic reef sites throughout the inner islands were monitored using fine
scale monitoring techniques. Monitoring efforts were continued by Reefcare International, a
non-governmental organisation based in Australia. The protocols established by Reefcare
International provided a foundation for those adopted by GVI. Although GVI’s logistical
constraints restrict monitoring efforts to the north-west coast of Mahé at sites selected by
SNPA.
The survey data collected by GVI volunteers allows for analysis of trends in coral reef health
seen over the past 13 years of monitoring. Along with this core research GVI Seychelles also
endeavours to aid in any of the other projects undertaken by all their partners where it can;
as it is hoped that with this help they will be able to increase their capacity to monitor,
manage and ultimately conserve the marine environment of the Seychelles for the future.
The GVI expeditioncomprises of survey programs that are four, eight or twelve weeks long,
running continuously throughout the year from January - December. Within the 12 months
fish and invertebrates are surveyed continuously at all survey sites in set time periods. Line
Intercept Transects and Coral Diversity transects are undertaken in the first 6 months to
evaluate coral coverage and site diversity, and Coral Recruitment quadrats are used within
the second 6 months to survey newly recruited colonies and gain a picture of site recovery.
Health and Safety: The safety of all volunteers is paramount. All volunteers are given a
health and safety brief on the camp upon arrival and conservative diving guidelines are
10
adhered to for the duration of the expedition. In addition, volunteers complete the PADI
Emergency First Response first aid course, and are taught how to administer oxygen in the
event of a diving related incident.
1.1 Survey Sites
GVI surveys a maximum of 24 separate sites around north-west Mahé in the course of a
year(fig1.1.).The 24 sites are surveyed twice a year; once in the first 6 months and then
again in the second half of the year. All sites are now listed as ‘core sites’(see Appendix A
for site details). The sites are evenly divided between carbonate and granitic reefs and they
represent varying degrees of exposure to wave action and currents. Six of the sites are
within Marine Protected Areas (MPAs) where restrictions on all fishing as well as regulations
on the recreational use of the park are in place.
Figure 1.1 Location and Substrate Type of GVI Survey Sites.
Each survey site is divided into ‘shallow’ and ‘deep’ zones, where the shallow zone is
defined by the depth range 1.5– 5.0m and the deep zone is defined by the depth range 5.1–
15.0m. Each site has a central point, marked by a distinctive landmark on the coastline, and
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is further divided into left, centre and right areas (fig 3.1.). These areas are loosely defined
as such by their position with respect to the centre marker of the site. All depths are
standardised with respect to tidal chart datum so as to eliminate tidal influence.
2 Aims
The focus of January to June 2013 was on surveying commercial and reef fish species as
well as benthic assemblage around North-West Mahé. The specific aims of the phase were;
• Assess diversity and density of fish species across all survey sites
• Estimate size of commercially important fish species
• Diversity of hard coral genera across all sites
• Assess benthic assemblage, including evaluation of hard coral, soft coral, sessile
organisms coverage and substrate composition
• Monitor coral predation and algal grazing pressures through density estimates of
hard coral predators, sea urchins and specific fish feeding guilds
• Assess abundance and diversity of commercially targeted invertebrate species
including sea cucumbers, lobster and octopus
2.1 Species Lists
2.1.1 Coral
The list of surveyed scleractinian corals covers 50 separate genera (See Appendix B for the
complete species list). Corals are identified to genus level only as in-situ identification
beyond genus level is not possible in the case of some corals, and is also beyond the
requirements of the project aims. Volunteers are also encouraged to record the genus as
‘unknown’ if they are not able to confidently identify a coral beyond the family level, and
similarly to record ‘unknown hard coral’ where even the family is not determinable with a
level of confidence.
2.1.2 Fish
The fish species chosen for surveys are those that are likely to indicate status of the reefs
along with fishing pressure, but are not overly difficult to locate, identify and count as
specified by SNPA / SFA. For example, Surgeonfish are herbivores and grazers and thus
would influence the algal – coral dynamics within the reef ecosystem. Reef-associated
species of commercial concern are also surveyed. This data can be used to help determine
12
the status of the reefs and of the fisheries especially when compared with the data from
previous phases.
Fish are surveyed to the highest taxonomic resolution practicable, with most identified to
species level. The resolution depends on difficulty of identification, and also the species’
characteristics and the data requirements of our partners. The taxonomic level needed
varies according to the ecological function of the species within the ecosystem; for example,
if different species within a genus feed on different types of food, it is highly desirable to
distinguish them to species. However, volunteers are instructed to record only to the level to
which they are confident of the identification, thus if they are sure of the family but not genus
or species, they record only as an “unknown species” of that family. See Appendix C - E for
the list and taxonomic resolution of fish species surveyed.
2.1.3 Invertebrates
Invertebrate species, which influence and can indicate the health and conditions of coral
reefs are surveyed along with commercially viable species which are under fishing pressure.
The full list of surveyed invertebrate species is included in Appendix F - G.
2.2 Training
2.2.1 Dive Training
All volunteers must be at least PADI Open Water qualified to join the expedition. Volunteers
then receive the PADI Advanced Open Water course covering Boat, Peak Performance
Buoyancy, Navigation, Underwater Naturalist, and Deep dives. Particular attention is paid to
buoyancy as surveys are conducted in water as shallow as two metres and over delicate
reef ecosystems.
2.2.2 Species Identification
Volunteers are required to learn species identification of assigned group either one or a
combination of fish, benthic organisms or invertebrates along with all additionally recorded
species such as turtles, sharks and rays. Training is initially provided in the form of
presentations, workshops and informal discussion with the expedition staff in the classroom.
Self-study materials are also available in the form of electronic and hard copy flashcards, as
well as Indian Ocean identification publications. Knowledge is tested using assessment in
the classroom, for which a 95% pass mark is required. Volunteers are taken on identification
dives with staff members for in-water testing; their responses are recorded and the dives
13
continue until the volunteer has demonstrated accurate identification of all necessary
species/genera.
2.2.3 Survey Methodology
Volunteers receive on land briefings and lectures, navigation practice and in-water training in
the skills required to conduct reef surveys. Volunteers complete the PADI Coral Reef
Research Diver (CRRD) course, which is specifically developed for GVI and offered only at
GVI marine expeditions in Mexico and Fiji. All volunteers are trained in the use of a delayed
surface marker buoy and tape reels, plus any other survey equipment specific to the
research they will be conducting. The course also includes a series of lectures on various
aspects of the marine environment. Before completing any recorded surveys independently,
volunteers participate in practice surveys in which they are taught and assessed by a
member of staff.
Improvements to the quality of species identification training materials are an ongoing and
extremely important component to this marine expedition. Photographs taken locally of
species underwater are the best materials to use – they are accurate and portray how the
organism appears underwater. New electronic and hardcopy flashcards are produced to
enhance the self-study materials available and to develop the exams by the same means.
Volunteers are encouraged to donate their underwater pictures to add to the library.
3. Methodology
3.1. Coral
3.1.1. Line Intercept Transects (LIT)
The LIT is a cost-effective method for assessing reef composition (Leujak & Ormond 2007)
which produces good results, replicates easily and can be taught to volunteers within time
and knowledge constraints. At every site, six 10 metre LITs were carried out, each running
parallel to shore within the specific depth range and using reeled tape measures. Three
LITs were completed in both the shallow and deep zones, evenly spread amongst the left,
centre and right of the site (Fig. 3.1.). Divers record a start and end depth for each transect.
The benthic assemblage and substrate is recorded in a continuous series of data of what is
directly under the tape, with start and end points for each entry, to the nearest cm. Where
coral is found, it is identified to genus level and the life form describing the majority of the
colony is recorded. Transects were laid randomly where possible, however placement of the
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2lb weight at the beginning of the transect generally meant avoiding delicate organisms,
therefore the start point would not be chosen randomly. Additionally, the topography at some
of the granitic sites creates limited possible places where 10 m of tape can be laid inside the
1.5 – 5.0 m zone and meant that shallow transects must be laid wherever the diver can
achieve it and thus diver selection must drive the process.
3.1.2 Coral Diversity Belt Transects
Two belt transects were conducted at each site to assess diversity of coral genera. The
transects start within the shallow zone at the centre of the site, heading out either to the
deep left (belt B) or to the deep right (belt A) at a 45˚ angle from shore; thus both the depth
and spread of each site is sampled (Fig 3.1). Divers conduct the survey by searching for
coral genera within a 2.5m bandwidth either side of the tape, completing tight s-shaped
search patterns, thus together surveying a 5m wide corridor along the 50m. Each diver
records the presence of any coral genera seen in their search area once.
3.2 Fish
3.2.1 Stationary Point Count
The stationary point count is a commonly used UVC technique (Kulbicki 1998, Engelhardt
2004) employed by well-respected reef assessment programs such as the Atlantic and Gulf
Rapid Reef Assessment (AGGRA) and the Florida Keys National Marine Sanctuary Coral
Reef Monitoring Program (FKNMS CRMP) (Hill & Wilkinson 2004). Variations of the method
have been used as part of several studies in the Seychelles (Jennings et al. 1995; Spalding &
Jarvis 2002; Engelhardt 2004; Graham et al. 2007) where the lack of spear fishing increases the
reliability of this technique (Jennings et al. 1995). The post-bleaching surveys conducted by
Reefcare International as part of the Seychelles Marine Ecosystem Management Project
(SEYMEMP) used 7 minute long stationary point counts and defined the area for the point
count with a 7m radius (Engelhardt 2001; 2004); 7– 7.5m radius circle has been shown to
create an area of the most suitable size for the size groups into which coral reef fish typically
fall (Samoilys& Gribble 1997). When GVI assumed responsibility for the continuation of this
assessment in 2005, the same methodology was adopted.
At each site eight stationary point counts were carried out. Four stationary point counts were
done in each of the shallow and deep zones, two centre, one left and one on the right (Fig.
3.2.). Divers recorded depth at the centre of each point count and start time for each survey.
A tape measure was used to delineate the circle radius, laid in any direction along the reef.
This allows for visual reference for the census boundary, increasing accuracy for density
calculations. Point counts were conducted by buddy pairs of divers where each was
15
responsible for counting a different selection ofsurveyed fish, thus reducing the number of
fish one person is required to count. During the last minute both divers swam around the
circle to attempt to ensure that more cryptic fish were counted.
3.2.2 50m Belt Transects
Colvocoresses and Acosta (2007) reported that Belt Transect surveys can cover more area
with a similar observer effort to Point Count surveys, although behavioural avoidance of fish
towards divers was frequently noted and, possibly as a result, lower densities of fish have
been recorded on Belt Transects than on Point Counts. We decided to introduce Belt
Transects in addition to the Stationary Point Counts, but to incorporate mechanisms to
reduce behavioural avoidance. Variety in methodologies also has the advantages of adding
to the skills set of the volunteers and enhancing their experience.
The transect belts were 50m long by 5m wide, a standard area often used for reef
assessments (Samoilys& Gribble 1997; Hill & Wilkinson 2004). Surveys were conducted by
buddy pairs with each diver responsible for counting a different selection of fish. Four belt
transects were completed at each site, 2 in the deep zone and 2 in the shallow (Fig. 3.2).
One diver laid a measuring tape parallel to the shoreline on the reef while the other swam in
front counting fish. Samoilys and Gribble (1997) recommend this technique of
simultaneously counting fish and laying the transect tape as it avoids disturbing the fish prior
to counting. After completion of the outward stage of the transect, the observers hover away
from the end of the tape for 3 minutes to allow fish to return to the survey area before
beginning the return leg. On the return journey, the second diver swims back along the tape
counting the other fish while the buddy reels in the tape behind them.
3.3 Invertebrates
3.3.1 10m Belt Transect
The diver conducting the invertebrate belt transects dives as a buddy to the coral LIT diver
and transects are conducted along the same tape as the LITs, thus six invertebrate belts
were completed at each site (Fig. 2.2). Invertebrate divers searched the area extending to 1
m either side of the tape for targeted species (see Appendix G).
3.3.2 50m Belt Transect
Extent of hard coral predation was measured as the density of two types of sea star; cushion
stars (Culcita spp.) and Crown of Thorns (Acanthaster planci), and gastropods in the genus
Drupella at each survey site, all of which are hard coral predators. Algal grazing pressure
was measured as the density of sea urchins. Two 50m transects were laid out at each site,
16
using polyprophelene reel tape measures. The transects start at the shallow centre point and
head out at opposing 45˚ angles towards the deep zone, thus covering the whole depth
range of 1.5– 15.0m and the spread of the site. Target species within 2.5m either side of the
tape were recorded (see Appendix F).
Figure 3. 1 Layout of coral LIT and diversity belts at each survey site, where the shoreline is represented by the top of the figure and the distance from shore indicates increasing depth.
Figure 3.2.Layout of fish SPC and belts, and 50m invertebrate transects at each survey site, where the shoreline is represented by the top of the figure and the distance from shore indicates increasing depth.
Stationary point count
Fish belt transect
Invertebrate belt
17
3.4 Environmental Parameters
During each survey dive the boat captain records abiotic factors pertaining to the
environmental conditions during the dive.
• Turbidity is recorded using a Secchi disk
• Cloud cover is estimated in eighths
• Sea state is evaluated using the Beaufort scale, a copy of which is kept on the boat
• Surface and bottom sea temperatures are recorded using personal dive computers
18
4. Results
4.1. Surveys Completed
During January to June 2013, substrate composition, commercial and reef fish species
density and mobile invertebrate density were recorded. For substrate composition surveys
23 survey sites were successfully completed, for fish density 22 survey sites were completed
out a possible 24 survey sites across the north-west Mahé coastline. Bad weather conditions
didn’t allow for a full composite of sites to be completed. Within each site all stationary point
counts, fish belts and LIT transects were completed. In addition 50m coral diversity transects
(excluding 2 core sites) and 50m invertebrate belt transects were surveyed (excluding 3 core
sites. This created a total of 176 SPCs, 88 fish belts (49,093m²), 138 LIT transects, 44 coral
diversity transects (12,380m²), 138 invertebrate transects and 42 invertebrate density belts
(13,260m²) across the completed sites.
In addition to the core surveys, in-water behavioural turtle surveys were conducted weekly
as well as turtle nesting surveys within the season of January to March. Data was also
collected on incidental sightings of mega-fauna including turtles, cetaceans, sharks, rays and
invertebrates of commercial importance.
4.2. Percentage mean live hard coral cover
Percentage hard coral cover was determined from the line intersect transects completed
across the 23 core survey sites. Percentage coral cover has seen an overall increase
between survey phases 2005 to 2013. Results from 2013 found coral cover reaching
maxima since surveys began at 37.64% (± 1.94) mean live hard coral cover. Overall mean
percentage cover has increased every year with the exception on 2009.
Percentage coverage of coral has continued its increase over the years, however when
results are analysed by substrate type (figure 4.1) differences in the rate of change can be
seen. Carbonate reef systems show stability in coral cover from 2011 at between 34 - 35%.
Results from 2013 found coverage of 34.51% indicating a decrease of 0.23% from 2012 but
still maintaining the current trend. The overall percentage coral cover remains higher for
granitic reefs, at 40.76% for 2013. A new maxima for coverage on granitic sites since
surveys began. This continues the trends found since 2005. Maximum difference between
the percentage cover between the two substrates was found in 2006 at 8.23%, although
fluctuating, this gap has now narrowed with time. Current results show a difference of 6.25%.
19
Figure 4. 1 Mean percentage coral cover (± SE) at the carbonate and the granitic sites, for each survey period from 2005 to 2013
4.3. Benthic Assemblage
Along with coverage of coral species, benthic assemblage is also recorded on the line
intercept transects. When combining the data from all sites results found for 2013 show a
higher percentage of algae at 53.22% than that of coral at 38.24%; with areas of bare
substrate (1.86%) and other benthic organisms (6.86%) showing significantly lower coverage
(figure 4.2). The various benthic organisms consist mainly of soft corals, sponges,
corallimorphs and zooanthids.
Figure 4. 2 Mean percentage coverage for coral, algae, other benthic organisms and bare substrate from all sites for Jan – Jun 2013
0
5
10
15
20
25
30
35
40
45 Mean Pe
rcen
tage Coral Cover % (±
SE)
Carbonate
GraniVc
Coral Cover %
Algal cover %
Various %
Bare %
20
Although sites show high coverage of algae the actual distribution of coverage differs when
looking at site specifics. It is observed that sites that show low coral cover have significantly
higher algal cover; this is also true with the reverse. Special reference to survey sites, Baie
Ternay Centre and Anse Major reef. Figure 4.3 also displays a difference in percentage
cover of both algae and coral distribution across an east-west gradient, with coral more
abundant to the west. In addition to this, comparison of algal vs. coral dynamics can be
analysed with regard to marine protected areas, overall algae still shows higher percentage
coverage than that of coral in both areas, yet within the marine parks the range is smaller.
Specific results show 54.33% algae vs. 37.24% coral outside the marine parks with 50.08%
algae vs. 41.06% coral within.
Figure 4. 3 Large scale spatial distribution of percentage coverage of coral, algae, various benthic organisms and bare
substrate across all sites, running East to West across North West Mahé from 2013
Excluding the continual growth seen with the Scaleractinian corals, distributions of algae and
other benthic organisms can be analysed across both the carbonate and granitic substrates.
Coverage of these benthic organisms differs between the two reef substrates. Carbonate
reefs show a greater range in coverage of sessile organisms whilst granitic sites are
dominated by coralline algal; with all other species having stable low level densities (figure
4.4; figure 4.5).
Benthic organisms on carbonate reefs display wide ranges in densities, all however are
found at significantly lower percentages than coral; below 9% coverage. Fluctuations are
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
L'ilot N
orth Face
White Villa
Corsaire Reef
Aube
rge Re
ef
Site X
Whale Rock
Rays Point
Anse M
ajor Reef
Anse M
ajor Point
Willie's Ba
y Re
ef
Willie's Ba
y Po
int
Site Y
Baie Ternay North East
Secret Beach Reef
Baie Ternay Ce
ntre
Baie Ternay North W
est
Baie Ternay Lighthou
se
Port Launay South Re
ef
Port Launay West R
ocks
Concep
Von North Point
Therese North Point
Therese North East
Therese South
Bare %
Various %
Algal cover %
Coral Cover %
21
seen with regards to each group, however relative dominance has remained stable
throughout the monitoring program. The exception is macro algae, which remains the least
abundant organism found on carbonate reefs (figure 4.4). There has been a decline in the
coverage of the two most abundant benthic organisms, Corallimorphs / Zooanthids, and soft
corals over the past two years. These changes range between 2 - 4%, fluctuations of this
size have been seen in previous years. Coralline algae shows an increase in coverage from
2010 and exceeds the coverage of soft corals this year, again fluctuations are seen in the
coverage year on year.
Figure 4. 4 Mean percentage coverage of algae and benthic organisms on surveyed carbonate reefs from 2005 – 2013.
The benthic assemblage of granitic reefs differs from that of carbonate reefs and is
dominated by coralline algae. The percentage cover of coralline algae at the granitic sites is
consistently higher than that of other benthic organisms (with the exception of coral).
Percentage coverage has seen a reduction from the peak at 10.56% in 2006. Current
coverage found for 2013 is 7.55% yet this algal group still remains dominant. Interestingly
the minimum coverage of coralline algae was seen in 2010 for both carbonate and granitic
reefs. Since then there has been an increase in coralline algae for each substrate type. All
other surveyed benthic organisms have shown consistent low level coverage of below 4%
with little fluctuation in coverage throughout the phases (figure 4.5).
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
2005 2006 2007 2008 2009 2010 2011 2012 2013
Mean Pe
rcen
tage Coverage %
Soe Coral
Sponge
Corallimorphs / Zoanthids Coralline Algae
Macro Algae
22
Figure 4. 5 Mean percentage coverage of algae and benthic organisms on surveyed granitic reefs from 2005 – 2013.
4.4. Structural Complexity
Structural complexity of the reefs is derived from the coverage of coral life forms which
increase the physical matrix of the reefs; primarily the branching and sub massive life forms.
Encrusting and massive coral life forms, although responsible for building up the reef
structure, provided limited habitat space for other reef inhabitants. The coverage of coral life
forms is independent from abundance of coral genus as a single genus can exhibit a
multitude of life forms.
Figure 4. 6 Percentage coverage of hard coral found across all reefs further divided by coral lifeform prevalence from
2005 - 2013
Figure 4.6 shows that across all sites the percentage coverage of coral has increased, along
with this there have been changes in the abundance of the key lifeforms related to the
structural complexity of the reefs.
0.0
2.0
4.0
6.0
8.0
10.0
12.0
2005 2006 2007 2008 2009 2010 2011 2012 2013
Mean Pe
rcen
tage Coverage %
Soe Coral
Sponge
Corallimorphs / Zoanthids Coralline Algae
Macro Algae
0
5
10
15
20
25
30
35
40
2005 2006 2007 2008 2009 2010 2011 2012 2013
Percen
tage coverage of coral %
Mushroom
Submassive
Massive
Foliose
EncrusVng
Branching
23
Figure 4.7 shows the changes in the percentage coverage of lifeforms out of the total coral
cover through the monitoring program. An increase in the abundance of branching coral is
clearly identifiable. In 2005 branching corals made up just 6.13% of the total coral cover, this
has increased year on year reaching its current maxima of 50.65% for 2013. In 2011
branching coral became the overall dominant coral lifeform a trend that has continued in this
year surveys results. Results from 2013 show branching corals making up 50.65% of hard
coral cover with encrusting corals making up 32.65%. Massive coral lifeforms have also
decreased in coverage from 2005 – 2013.
Figure 4. 7 Percentage coverage of coral lifeform found across all reefs from 2005 – 2013
Overall distribution of coral life forms differs significantly depending on substrate type.
Branching life form dominates the carbonate reefs whereas encrusting life forms dominate
the granitic (figure 4.8, figure 4.9). The higher rate of growth in the branching corals on the
carbonate reefs is the reason for the dominance. Granitic reefs have displayed increased
coverage of branching corals, however the rate is markedly slower than that seen on the
carbonate reefs.
Figure 4. 8 Percentage of coral life forms on carbonate sites 2005 – 2013
0
10
20
30
40
50
60
70
80
90
100
2005 2006 2007 2008 2009 2010 2011 2012 2013
Mushroom
Submassive
Massive
Foliose
EncrusVng
Branching
0
20
40
60
80
100
2005 2006 2007 2008 2009 2010 2011 2012 2013
Mean Pe
rcen
tage Coverage
%
Mushroom
Submassive
Massive
Foliose
EncrusVng
Branching
24
Figure 4. 9 Percentage of coral life form on granitic sites from 2005 – 2013
4.5 Coral Diversity
Survey of coral diversity found a total of 42 different genera from 14 families of Scleractinian
corals for 2013. Figure 4.10 shows the mean number of genus found at each site, divided by
substrate type. Results found mean coral diversity across all sites to be 30.50 coral genera
per site. From 2005 an initial increase in coral diversity which continued until 2007, from this
point on coral genera have remained stable at around a mean of 30 per site. Throughout the
surveys the difference between diversity at both the granitic and carbonate reefs has been
relatively stable, which is seen in the 2013 results. For 2013 granitic sites showed a mean
coral diversity of 30.23 and carbonate sites showed 30.78 genera per site.
Figure 4. 10 Comparison of mean coral genera richness (± SE) for carbonate and granitic sites from 2005 – 2013.
0
20
40
60
80
100
2005 2006 2007 2008 2009 2010 2011 2012 2013
Mean Pe
rcen
tage Coverage %
Mushroom
Submassive
Massive
Foliose
EncrusVng
Branching
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
2005 2006 2007 2008 2009 2010 2011 2012 2013
Mean Gen
era Richne
ss per site( ±
SE)
Carbonate
GraniVc
25
4.6 Overall Fish Results
Overall abundance for all surveyed commercial and reef fish species using both point count
and belt methodologies came to 12,548 individuals across a total survey area of
49,093m2,giving an average fish density of 0.30 individuals per m2. Per specific survey site,
the two sites showing the highest total abundance levels were Baie Ternay Lighthouse and
Therese North End, with 907individuals (0.41 per m2). The next closest site in terms of
overall density was Baie Ternay North West with 843individuals (0.38 per m2). The lowest
abundance levels were found at Willie’s Bay Reef, 406individuals (0.18 per m2), and Anse
Major Reef, 420 individuals (0.19m2).
All three sites showing the highest densities of fish are granitic sites and are located at
exposed areas. Benefits of exposed areas include having higher current and nutrient
availability. There is also a higher percentage of coral cover at granitic sites (see figure 4.1).
Complexity of the reef habitat has been linked to diversity of fish populations in some
studies, but not necessarily to fish abundance (Chabanet et al. 1996). This stems from the
variation in different niches it provides. Two of the sites are also located within the Baie
Ternay Marine Park, therefore benefitting from the protection of this no take zone.
Willie’s Bay Reef and Anse Major Reef showed some of the lowest coral coverage of all
sites surveyed during this phase, therefore suggesting that these sites are lacking in the
structural and ecological complexity that the coral cover provides. They are also located
towards Bel Ombre and Beau Vallon, which are areas of high boat and fishing activity.
4.7 Combined Fish Density 2005 – 2013
The data used to analyse fish abundance over all sites is taken from the stationary point
count surveys, as the belt transect was only introduced into GVI’s set survey methodology in
2009. The analysis of all data up to 2011 has also been modified to adapt to the new
surveyed species list revised in 2009 and 2010, and all pre-existing data from 2005 onwards
has been adapted to represent this. This finally allows for correct interpretation of the feeding
guilds and total fish density across all of the survey years, and hence any relevant
fluctuations in density or predominance of guilds can be accurately seen.
The mean density of fish for January to June 2013 was found to be 0.30 individuals per m2,
very similar to the findings from 2011 and 2012. The mean density of fish over all survey
sites shows minor fluctuations throughout the years, however the density has never been
26
seen to rise or fall outside of 0.25 and 0.35 per m2 since 2005 (figure 4.11). This suggests
that populations are relatively stable, and could be oscillating around a maximum carrying
capacity or have stabilised at the current fishing pressure.
Figure 4. 11 Mean density per m² of all surveyed fish species across all survey sites, 2005 - 2013.
When dividing the densities between site substrate (granitic vs. carbonate) the results from
January – June 2013 show that granitic sites had a higher density than carbonate (figure
4.12). This has been consistent since 2011, however prior to this there have been
fluctuations in substrate relative richness since surveys began. This is interesting in itself, as
the two substrate compositions have greatly differing environments and food resources for
fish species, so would theoretically harbour varying levels of fish density per m².
Figure 4. 12 A comparison of mean density per m² of all surveyed fish species between carbonate and granitic
substratesites, 2005 – 2013
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
2005 2006 2007 2008 2009 2010 2011 2012 2013
Mean de
nsity
of fi
sh per m
2
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
2005 2006 2007 2008 2009 2010 2011 2012 2013
Mean de
nsity
of fi
sh per m
2
GraniVc Carbonate
27
4.8 Fish Densities with regards to Feeding Guilds
By analysing fish abundance by their functional role in the marine ecosystem it can give an
indication of changes within the community that may not initially be apparent by studying
population changes of individual species (Micheli & Halpern 2005). Analysis using feeding
guilds; determined by the primary food source of individual species, is a common approach
to assessing functional diversity. These feeding guilds and the species that fall within them
are taken from Obura and Grimsditch (2009), and further adapted to the specific species
found within Seychelles in agreement with our partners. A full list of the relative guilds and
the divided species can be found in appendix C. As with fish density results, the density of
feeding guilds is also only taken from the stationary point counts to eliminate the
consequences from the change in survey methodology in 2009.
The most dominant feeding guild across all sites is herbivores (figure 4.13), comprising
surgeonfish (Acanthuridae), rabbitfish (Siganidae) and parrotfish (Scaridae). This is normal
for most ecosystems as they support the higher trophic levels. This guild has remained at a
relatively stable abundance during all survey years, increasing slowly in density from 2006
onwards. 2013 is beginning to rise slightly from the drop in numbers seen in 2011; the first
downward turn for herbivores seen since 2006.
Figure 4. 13 Comparison of fish feeding guilds through density per m² across all sites, 2005 – 2013.
If we look at feeding guilds excluding herbivores (Figure 4.14), there are relatively small
fluctuations for most guilds. We see a decline in planktivores and those with varied diet, with
piscivores being one of the only guilds to remain relatively stable. All other guilds show
some form of increase, however this is most notable in the corallivores. This guild consists of
0
0.05
0.1
0.15
0.2
0.25
2005 2006 2007 2008 2009 2010 2011 2012 2013
Density
of Fish Species p
er m
2 PlankVvores
Piscivorous
Corallivores
Varied diet
InverVvores
Herbivores
Corallivore / Herbivore
Corallivore / InverVvore
28
obligate coral feeders within the butterfly fish family Chaetodontidae and has displayed the
greatest change in abundance across the survey years, increasing from 0.006 in 2005 to
0.055 per m2 in 2013.
Figure 4. 14 Comparison of feeding guilds through density per m² across all sites, 2005 – 2013, disregarding
herbivores.
To explore why corallivores have had such a relatively rapid and consistent increase,
corallivore density was overlaid with mean percentage coral cover since 2004 (Figure 4.15).
Both show a continuous increase, except in 2009 where a dip in coral cover ties in with a
plateau in corallivore density. By adding trend lines to look at the linear relationships
between these two sets of data it suggests that they are highly correlated.
Figure 4. 15 Comparison of linear trend lines for coral cover and corallivore density across all sites from 2004 to present.
0
0.01
0.02
0.03
0.04
0.05
0.06
2005 2006 2007 2008 2009 2010 2011 2012 2013
Density
per m
2
Survey Phases
Corallivores
Piscivorous
Varied diet
Corallivore / Herbivore
Corallivore / InverVvore
InverVvores
PlankVvores
-‐0.01
0
0.01
0.02
0.03
0.04
0.05
0.06
0
5
10
15
20
25
30
35
40
45
2004 2005 2006 2007 2008 2009 2010 2011 2012 2013
Corallivore den
sity per m
2
Mean pe
rcen
tage Coral Cover %
Coral Corallivore
29
By plotting mean percentage coral cover against corallivore density we can test the
correlation between the two data sets. Figure 4.16 shows a highly correlated exponential
increase (R2 =0.926), supporting the idea that these two data sets are related, and that an
increase in coral cover results in an increase in corallivore density. Further study is required
into other factors affecting corallivore density to better understand how important coral cover
is to corallivore populations.
Figure 4. 16 Mean coral cover against corallivore density for all sites from 2005 to present.
4.9 Influence of Marine Protected Areas on Fish Densities 2005 – 2013
In analysing the data between the mean density of fish per m2 within marine protected areas
(MPAs) and unprotected areas there is a consistently higher density within MPAs (figure
4.17). With the exception of the Jan- Mar 2010 survey phase, MPAs have had an average
greater density of 0.047 per m2 ± 0.024 SE.
Figure 4. 17 Overall mean density per m of fish inside and outside marine protected areas, Nov-Dec 2005 to Jan-Jun 2013.
0
0.01
0.02
0.03
0.04
0.05
0.06
0 5 10 15 20 25 30 35 40
Corallivore den
sity per m
2
Mean coral cover %
0 0.05 0.1
0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5
Mean De
nsity
s of fi
sh (p
er m
2 )
Survey Phases
Overall Protected
Overall Unprotected
30
Separating the sites into granitic and carbonate reveals that this substrate has no influence
on mean density levels of fish; the protected sites on either type harboured a higher density
overall (figure 4.18; figure 4.19).Carbonate sites within MPAs have always held a higher
density of fish since 2005, with the January – June 2013 phase containing a mean density of
0.380 per m2 within MPAs compared to 0.279 per m2 in the carbonate sites outside protected
zones (fig. 4.18).
Figure 4. 18 Mean density of fish per m² on carbonate substrate sites inside and outside marine protected areas, Nov-Dec 2005 to Jan-Jun 2013.
Granitic sites have had a much less significant difference between the years, continuously
fluctuating in relevant densities. The January - June 2013 results show that mean density for
granitic unprotected sites is currently slightly higher at 0.370 per m2 compared with 0.322 per
m2within protected zones (figure 4.19).
Figure 4. 19 Mean density of fish per m on granitic substrate sites inside and outside marine protected areas, Nov-Dec
2005 to Jan-Jun 2013.
0.00
0.10
0.20
0.30
0.40
0.50
0.60
Carbonate Protected
Carbonate Unprotected
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45
GraniVc Protected
GraniVc Unprotected
31
4.10 Fish Species Diversity
Diversity refers to the species-richness, or number of separate species, within the survey
site as opposed to the relative abundance of fish. The site found to have the highest
diversity in 2013 was Baie Ternay Lighthouse with 47 species. The lowest diversity was
found at Anse Major Reef with 28 species and Corsaire with 32 (figure 4.20). In addition,
comparing sites inside Marine Protected Areas to those outside revealed that MPAs
contained a higher number of species on average than non-protected areas with 39 species
in MPAs and 38.4 in areas outside.
Figure 4. 20 Species-richness (number of fish species found) across all survey sites along NW Mahé, 2013. Green
denotes sites within Marine Protected Areas and blue denotes non-protected sites.
A comparison of species-richness between the same sites surveyed in 2005 and the results
from 2013 reveal a significant increase in the number of surveyed fish species present
across all areas (figure 4.21); with a mean increase of 9.79 species (± 1.56 SE) over all
sites. Therese North End was the only site to see a decrease in species richness. This has
been the trend for this site for the last 2 years, which is interesting as this site is not
characterised by seeing much anthropogenic activity. More research into why exactly this
site is dropping in diversity would be insightful.
0 5 10 15 20 25 30 35 40 45 50
No. of ind
ividua
l spe
cies su
rveyed
32
Figure 4. 21 A comparison of species-richness (number of fish species) between the same sites of NW Mahé in 2005 and in 2013.
4.11 Commercial Fish Sizing Results
All volunteers are assessed on their ability to estimate size of the commercial fish species
when sighted underwater. Assessment was carried out by use of on-land training, where
volunteers are asked to size objects from varying distances and instant feedback is given.
On-land testing is also given by sizing a line with artificial fish attached from a distance of no
closer than 2m. In-water assessment was carried out using a line with sections of
polyurethane piping of known length. Volunteers estimate the lengths underwater and results
and feedback are given after each dive. Along with practice methodology, assessment is
also undertaken within the fish survey practice methodology under the supervision of a staff
member. All volunteer’s estimates are checked against the staff’s recording. Only when a
volunteer displayed 100% accuracy in sizing fish to the 10cm bandwidth on both in-water
piping assessment and the practice surveys were they allowed to conduct surveys. All
volunteers from the past survey phase could accurately define the size of all commercial fish
species to within the 10cm bandwidth required.
0 5
10 15 20 25 30 35 40 45 50
No. of surveyed species p
resent
2005
2013
33
4.12 Invertebrate Densities from 10m Transects
Specific surveyed invertebrate species have increased across all sites since surveys began
in 2005 with the exception of Platyhelminthes and Black Spined Urchins, which are found at
stable densities. The most significant increases in density are seen in the Arthropoda and
Mollusca phyla. The Arthropoda phyla has increased from low level densities found in 2005
of 0.01 individuals per m2 up to the most abundant invertebrate found in 2013, the Mollusca
phyla has shown a similar increase with time until 2012; results from 2013 shows a drop in
the density of 0.67 individuals per m2. Echinodermata phyla has also been increasing
throughout the survey program but results from 2012 - 2013 shows a consecutive reduction
in the density, falling from 1.64individuals per m2 in 2011 to 1.32individuals per m2 in 2013
(figure 4.22).
Figure 4. 22 Mean density (individuals per m²) of invertebrate phyla and black spined sea urchins at carbonate reef
sites, for every survey period from 2005 to 2013
When the results are divided by substrate type the invertebrate densities show differences
between them. Granitic sites show a greater spread in the densities of the surveyed
invertebrates. The Arthropoda phyla has increased significantly from 2005 but there is a
marked increase in their abundance from 2008, results for 2013 show Arthropoda phyla to
be the dominant group on granitic sites. This has mainly been due to the significant
decrease in the Mollusca phyla in 2013 reducing by 1.1 individuals per m2 in a single year,
this large change in density over a single year is seen in the results previously. In 2010
Mollusca increased by 1.4 individuals per m2 in a single year (figure 4.23).
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60
1.80
Inverteb
rate Den
sity (ind
ividua
ls/m
2 )
Annelida
Platyhelminthes
Arthropoda
Mollusca
Echinodermata
Black Spined Sea Urchins
34
Figure 4. 23 Mean density (individuals per m²) of invertebrate phyla and black spined sea urchins at granitic reef sites,
for every survey period from 2005 to 2013.
Carbonate reef sites have shown a decrease in all survey invertebrates in 2013 however the
relative dominance of the phyla remain consistent with 2012, with highest abundance being
Echinodermata. Black Spined Urchins have continued the decrease, which started in 2010
and is now at a minima for the survey program of 0.45 individuals per m2 (figure 4.24).
Figure 4. 24 Mean density (individuals per m²) of invertebrate phyla and black spined sea urchins at carbonate reef
sites, for every survey period from 2005 to 2013.
0.0
0.5
1.0
1.5
2.0
2.5
3.0 Inverteb
rate Den
sity (ind
ividials/m
2 ) Annelida Platyhelminthes
Arthropoda Mollusca Echinodermata Black Spined Sea Urchins
0.0
0.5
1.0
1.5
2.0
2.5
Inverteb
rate Den
sity (ind
ividials/m
2 )
Annelida Platyhelminthes Arthropoda Mollusca Echinodermata Black Spined Sea Urchins
35
4.13 Invertebrate Densities from 50m Belts
In total 42 invertebrate abundance belts were completed across all the 21 sites surveyed,
covering a total area of 10,500m2. The trends in density levels found during 2013 continue
those found with all previous survey phases. Short-spine (Echinothrix sp.) at 0.30 per m2 SE
±0.04 and long-spine (Diadema sp.) at 0.11 per m2 SE ±0.03 (figure 4.25) still show the
highest abundance of all the surveyed invertebrates; significantly higher than all other
invertebrate species found.
Figure 4. 25 Mean density per m2 of all surveyed invertebrate species across north-westMahé, 2013.
When dividing the two most abundant invertebrates by substrate type some interesting
trends can be observed (figure 4.26). Short-spine sea urchins show a preference to granitic
substrate, indicated by the higher density levels at these sites; whereas long-spine sea
urchins display similar density levels over both substrates; not indicating any preference.
Through the monitoring program short spine urchins have been decreasing at a steady rate
on carbonate sites and a similar decrease is seen from 2011 on the granitic sites, after an
initial rise in 2010. Long spine urchins have been much more stable in numbers from 2009,
however 2013 results show a decrease in number at the granitic sites which hasn't been
seen previously in the monitoring program.
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
Mean de
nsity
per m
2
Invertebrate Species
36
Figure 4. 26 Mean density per m2 of all surveyed invertebrate species across north-westMahé from 2009 - 2013.
Figure 4.27shows the density levels of the major corallivorous invertebrates of Crown of
Thorns seastar (Acanthaster planci), Cushion Starfish (Culcita spp.) and Drupella
snails.Studies of the trends in the corallivorous invertebrates show significant, almost
alarming, increases in abundances for the Drupella sp. in recent years, however the density
has decreased for 2013 these species still remain in much higher abundance levels than the
other corallivorous invertebrates.
Figure 4. 27 Mean density per m2 of Cushion Seastar (Culcita spp.), Crown of Thorns (Acanthasterplanci) and the gastropods Drupella sp. from 2009 - 2013 across all sites.
0.00
0.10
0.20
0.30
0.40
0.50
0.60
2009 2010 2011 2012 2013
Mean de
nsity
(per m
2 )
Long Spine Carbonate Short Spine Carbonate Long Spine GraniVc
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
2009 2010 2011 2012 2013
Mean De
nsity
per m
2
Cushion
Crown of Thorns
Drupella
37
4.14 Sea Cucumber Densities
The total number of sea cucumbers found across all survey sites of north-west Mahé was
280 individuals for 2013 across the 21 sites surveyed. Figure 4.28 shows the total number of
sea cucumbers divided by the number of sites surveyed for each year. This graph clearly
displays after the initial rapid decrease in abundance of sea cucumbers seen in 2007 the
populations are increasing across all the survey sites.
Figure 4. 28 Mean Number of sea cucumbers recorded per site from 2006 - 2013.
Analysis of individual sea cucumber species reveals that both Pearsonothurian graeffei and
Stichopus spp. remain the most abundant sea cucumbers across all sites (figure 4.29).
Interestingly, the combination of a steep reduction in the density of Stichopus sp. and a
continued increase in Pearsonothurian graeffei numbers,has lead to Pearsonothurian
graeffei becoming the dominant sea cucumber species for 2013. High abundances of the top
3 is significant as they are of little commercial value, compared to the other surveyed sea
cucumbers which show lower abundance levels.
Figure 4. 29 Density per m2 of individual sea cucumber species across all survey sites of north-westMahé from 2008 - 2013.
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
16.0
2006 2007 2008 2009 2010 2011 2012 2013
No. Of C
ucum
bers fo
und pe
r site
surveyed
0.000
0.002
0.004
0.006
0.008
0.010
0.012
0.014
2008 2009 2010 2011 2012 2013
Density
per m
2
Holothuria atra
*Holothuria fuscopunctata
*Holothuria fuscogilva
*Holothuria nobilis
*Holothuria sp. (Pentard)
Bohadschia sp.
AcVnopyga sp.
*AcVnopyga mauuriVana
SVchopus sp.
*Thelenota ananas
Pearsonothurian graeffei
Holothuria edulis
Thelenota anax
38
5 Discussion
5.1 Coral Surveys
Overall mean coral coverage has increased significantly over the past seven years of reef
monitoring conducted by GVI across North West Mahé. Mean percentage coral coverage
has increased from 10.25% ± 1.27 SE in 2005 up to 37.64% ± 1.98 SE in 2013. Granitic
sites have reached a new maxima in percentage coral cover for the survey program in 2013
whilst cover at carbonate sites has reduced by 0.23% since 2012. However overall since
2010 the rate of coral growth seems to have slowed; coral cover only increased by 3.21%
between 2010 and 2013, around half the rate for 2008 - 2010 an 8.16% increase. Yet,
overall any increase in cover is encouraging for the continued regeneration of the reefs after
the mass coral bleaching event in 1998.
Granitic sites have maintained the higher coral coverage throughout the survey program.
Engelhardt (2004) attributes the elevated coral cover at granitic sites to higher water clarity
linked to their position. Granitic sites are found at more exposed points with high water flow,
whereas many carbonate sites are within sheltered bays receiving lower water flow rates
resulting in higher nutrient and sediment levels through run off from terrestrial sources. The
lower flow rates found in these sheltered bays means these high nutrient and sediment
levels persist which can negatively affect coral growth (Nugues & Roberts 2003; Ferrier-Page`s
et al. 2000; Ward & Harrison 2000). Overall percentage coral cover within the Marine Parks of
both Baie Ternay and Port Launay show higher coral cover. Inside the Marine Parks average
percentage coral cover was 41.06% whereas outside these protected areas was 37.24%
attesting to the importance of overall ecosystem health for resilience of the corals species.
Additional comparisons can be made between site specific data from the monitoring
conducted in 2005 directly to the results of 2013. Overall coral cover has increased
significantly between these yearsbut the rate of change is different depending on which
survey site is focused on. Highest coral cover found in 2005 was 16.67% at Therese North
End whereas for 2013 maximum was found at Baie Ternay Centre with 64.53%. The range
in coral cover (sites displaying highest and lowest coral cover) is also drastically different
between the years. 2005 displayed a range of 14.98% whereas 2013 displayed 45.91%
difference in coral cover. This indicates that the more derogated sites are lagging far behind
the sites with a higher rate in coral growth. In general there has been a three-fold increase in
percentage cover across all sites but Anse Major Reef and Willie's Bay Reef are increasing
at rates of around half the mean.
39
Continual benthic coverage is recorded for all line intersect transects, results averaged over
all sites for 2013 found 53.22% of coverage was algae compared to 38.24% for coral cover.
This shows algal dominance across all sites for 2013; however analysing the coverage of
algal species shows that 88.2% of the algae recorded was turf algae; this diminutive,
filamentous algal is associated with relatively pristine, healthy reef systems and is a major
contributor to high algal productivity (Steneck 1988; Klumpp & McKinnon 1989). While it is well
established that macro algae can outcompete and overgrow corals (Birkeland 1977; Hughes
1994; Jompa & McCook 2002a, 2002b) results from 2013 found this algal to compose just 0.1%
of total algal coverage.
Analysis of the other algae and epibenthic organisms, with the exception of Scleractinian
corals, shows low coverage of below 12.0% on both granitic and carbonate reefs. The
carbonate reefs show a larger range in the densities of these other organisms. Corallimorphs
/ Zooanthids and soft corals on carbonate sites have relative high densities, notable as they
compete rigorously with scleractinian coral for space (Lindèn et al. 2002); although densities
are still much lower than that of coral. Granitic sites show lower coverage of algae and
epibenthic organisms with the exception of coralline algae. Coralline algae coverage shows
a similar trend on both substrates. Increase in coverage from the minimum in 2010. High
coverage of coralline algae indicates consolidation of reef structure (Grimsditch et al. 2006).
This slow rise in the coverage of coralline algae could increase the consolidation of loose
rubble on the surface of the reef, which is important as loose rubble can damage adult coral
colonies, but has a more dramatic effect on the coral recruitment rates; as the abrasion can
damage and remove newly settled recruit corals (Turner et al. 2002).
Structural complexity of the reefs of the Seychelles is showing very positive recovery post
the 1998 bleaching event. Structural complexity of the reefs is important for the overall
health and diversity of the reef ecosystem, a complex reef structure allows for extensive
habitat space for other organisms such as fish and invertebrate species to flourish (Garpe et
al. 2006; Glynn 2006; Graham et al. 2006). Branching coral life forms have the effect of
increasing the physical matrix of the reef by increasing its structural complexity. Acropora
and Pocillopora species predominantly display the branching life forms (Veron 2000) these
fast growing species are hardest hit by coral bleaching events (McClanahan et al. 2004), but
also fastest to recover. Previous coral surveys from Seychelles post 1998 found very low
coverage of the coral species Acropora and Pocillopora. Whereas the massive species,
those that are more resilient to coral bleaching, such as Porites and Goniopora dominated
40
the coverage (Engelhardt et al. 2003). Branching coral cover continued to increase on both
substrates in 2013, following the trend seen throughout the monitoring program. Since 2010
the encrusting life form has made up around 30% of the corals surveyed whereas branching
corals have increased from 40% to 50% in the same time period. The continued growth of
this life form is a positive sign of reef recovery and increasing structural complexity, which
has the potential to support a greater abundance and diversity of reef organisms.
Differences in the structural complexity of the two substrate types is also evident. Carbonate
reefs currently maintain a very high percentage of branching corals; making up 61.37% of
corals found. Granitic sites have been continuously dominated by encrusting corals which
contribute little to structural complexity of the reefs, however the granitic sites have inherent
complexity from granitic boulders located across the sites; this is a common feature of all the
granitic sites that are surveyed. On granitic sites the coverage of encrusting corals has been
slowly decreasing as the branching corals increase and if these trends persist within the next
few years branching corals will dominant both granitic and carbonate reef substrate.
The diversity of coral on the surveyed reefs has increased through the monitoring program.
Initially a rapid increase in the mean diversity was seen up until 2007, then stabilised from
this point at a mean diversity of around 30 genera per site. Diversity divided by carbonate
and granitic reefs has always been similar and the results from 2013 are no exception,
finding an average of 30.5 genera on both the substrate types. It is interesting to note that
although the number of different genera found overall seems to have stabilised, the spread
of coral genera found at every site is increasing. Through analysing the number of coral
genera found at every site; in 2005 only four coral genera were found at each, however in
2012 15 coral genera were found at every single site. Indicating that although overall
diversity has remained relatively stable the corals already established on some of the reefs
are settling into new areas.
41
5.2 Fish Surveys
This section of the report contains results from surveys conducted between January to June
2013, assessing the abundance and diversity of both reef and commercial fish species. The
true value of the data set is in the contribution it makes to the larger data set over the last 8
years of surveying. This not only gives important insights into the status of coral reefs around
Mahé, but also helps increase knowledge on reefs around the world, and helps us to
understand how reefs in general can recover from bleaching events such as in 1998.
After 1998 reefs around the North-West of Mahé saw up to 90 per cent coral mortality,
resulting in a huge drop in coral cover and diversity. The main life forms that survived were
the more resilient massive and encrusting corals, such as those within the Faviidae and
Porites families. This affected many of the biotic and abiotic resources for reef fish, and
subsequently affected the composition of the reef fish community. One way of assessing
these changes is to look at the trends of the functional diversity of the community (Figure
4.13). Breaking down the data by feeding guilds can indicate phase shifts within the coral
reef ecosystem. Herbivores and piscivores show very little changes throughout survey
history, with only a few fluctuations. Without having direct reliance on the scleractinian coral
itself the dramatic decrease in coral coverage would not have had the same impacts on
resource availability for these guilds. In fact, the decrease in coral coverage had a reverse
effect on algal growth, with the algae coverage at an all-time high in the years directly
following the bleaching. The stable populations of herbivores on the reefs kept this bloom in
check, allowing the slow regrowth of coral.
It is interesting to see a gradual but steady decline in planktivores across our survey sites, as
their resources come solely from the water column and are therefore unaffected by the
phase shifts in the coral beneath them (Sluka & Miller 2001). Plankton density is related to
changes in water temperature and coastal currents. When the winds switch direction in May
and June, this results in upwelling around the North-West of Mahé bringing cold, nutrient rich
water towards the surface. This results in cycles of phyto and zooplankton blooms until the
winds switch once more in September. Analysing fish densities on a yearly basis excludes
these short term cycles, and does not explain the gradual decline. More research into factors
affecting plankton density over long timescales is required in order to explain this trend.
Studies have indicated that the most notable changes to reef fish communities following a
large scale stochastic event, such as in 1998, are most apparent in specialist species
(Graham et al. 2007). We can see this in the data set with the changes to the density of
42
corallivores. Corallivores have gone from being one of the lowest feeding guilds when
surveys began to one of the most dominant, second only to herbivores (figure 4.13). The
corallivore guild comprises of 6 species, but density increase has primarily been seen for
Chaetodon trifasciatus,Chaetodon trifascialis andChaetodon zanzibariensis. It may be that
for the obligate corallivores within the butterflyfish family these 3 are the most competitive
species.The increase in coral cover and corallivore density show similar linear trend lines
(figure 4.15), and by plotting these together we can see that they are highly correlated (figure
4.16). It makes sense that as their main food source increases so too does the population.
Not stating that coral cover is the singular variable controlling corallivore densities, but it
suggests that it is highly influential.
Since 2005 diversity in coral life forms has increased, with branching now being one of the
dominant life forms. Studies have linked complexity of the reef substrata with fish diversity,
but not necessarily fish abundance (Chabanet et al. 1996; Luckhurst & Luckhurst 1978; Talbot et
al. 1978; Roberts & Ormond 1987). This can be seen in the data set whereby mean density of
all fish surveyed does not change very much throughout survey history, it is the composition
of species that changes. Branching corals, such as Acropora spp. provide areas for refuge
for small fish and invertebrates, helping to increase diversity and create a more complex
food web. This is extremely important, as reefs with a more natural and diverse composition
of fauna are more likely to recover from stochastic events. If ecosystems are built upon a
simplified food chain, then if one species is removed this affects the entire chain. For those
ecosystems that are more complex and varied, if one species suffers and is lost from the
food web, other options for food and resources are still available and species can adapt. A
number of studies support this theory whereby an increase in coral diversity results in an
increase in micro-habitats which in turn supports a wider variety of species (Carpenter et al.
1981; Sano et al. 1984, 1987; Bell and Galzin 1984, 1988, Barbault 1992).
MPAs within Seychelles are designated zones where the removal of any species is illegal
and the anchoring of boats and level of tourism is monitored. These no-take zones
provideimportant refuge areas for targeted fish species, but also may potentially benefit fish
stocks through the theory of ‘spillover’, the net export of adult fish, from an area of high
density to adjacent non-protected areas of lower fish density (Abesamis & Russ 2005). A
number of studies show evidence that density of species targeted by fisheries increases
within MPAs (Gell & Roberts 2002, Halpern 2003, Sobel & Dahlgren 2004). The results show that
MPAs do harbour a higher mean density of fish per m2, with an average of 0.35 fish per m²
found within the MPAs compared to 0.32 per m² outside. Carbonate sites typically hold
higher density levels inside protected zones, whereas granitic sites constantly fluctuate
43
between dominance. This could be in part due to the fact that these deeper and typically
more exposed sites usually home species within the families Lutjanidae and Lethrinidae
which tend to be less territorial than those that are more closely associated with the
carbonate reefs. It is also interesting to note that sites immediately adjacent to MPAs, such
as Baie Ternay Lighthouse and Site Y also have comparatively high numbers of fish. Site Y
had the highest density of commercial fish species out of all survey sites at 0.16 individuals
per m². These sites also showed high greater species diversity (figure 4.20). This supports
the theory that MPAs help to protect and create a more natural complex ecosystem.
Despite clearly holding healthier abundance levels of fish, it is difficult to measure the
effectiveness of MPAs due to many reasons, and multiple studies have attempted to do so
(Field et al. 2006). It is also difficult to control for the selectiveness of MPAs. Most MPAs are
chosen for their higher densities and species-richness of fish and other organisms, as well
as their potential for recruitment and juvenile species’ habitat. It is reasonable, then, that in
studying the densities of fish within and outside of the protected areas that the MPA would
hold a higher number than non-protected areas as it originally did so. In analysing the data
of both fish densities and coral health since 1998, however, MPAs clearly recovered faster
than non-protected areas and have achieved higher density levels overall.
From the data we can see that MPAs are an important management tool to help protect
against over exploitation of target species and a reduction in undesirable fishing induced
impacts on non-target species and fishing-induced impacts to habitat (NRC 2001; Gerber et al.
2003; Halpern 2003). The continued protection of these areas is paramount to maintaining
healthy fish populations. The findings within this report highlight the need for thorough
management of both fish stocks and of coral reef areas to provide some insurance against
larger-scale disturbances, such as the 1998 event.
44
5.3 Invertebrate Surveys
Invertebrates have been studied as biological indicators within terrestrial and aquatic
ecosystems extensively, including coral reef habitats. Their importance lies in their
interactions with the reef habitat, and density may reflect changes in reef composition and
structure. Densities of surveyed invertebrates from the 10m belt transects have increased
since the beginning of the monitoring in 2005, however 2013 results show a reduction in all
survey invertebrates from 2012 with the exception of black spine urchins and
Platyhelminthes. Platyhelminthes show low densities due to their lifestyle; these species are
generally nocturnal and found mostly under the rock and rubble of the reef (Coleman 2000),
but are also hard to spot as most species are small and camouflaged.
Results from 2013 show a drop in density for all but two phyla, this is most noted in the
Mollusc's and Arthopod's and also this is the first reduction seen in both phylum since 2009.
Mollusca shows the greatest decrease overall which is primarily due to a reduction in the
number of oyster species Hyotissahyotis on granitic sites, which usually hold high
abundance.These bivalves attach to rocks or coral on reef faces and walls and are more
prevalent on these sites, but 2013 saw the large drop in numbers, whereas on carbonate
sites the density is has still seen a slight increase. The Arthropoda phyla has decreased in
density at carbonate sites. Again when looking at species changes within the Arthopoda
phyla the overall reduction in the mean is caused by a decrease in the numbers of crabs
seen on carbonate sites which has reduced by 0.28 individuals per m2, whereas density has
continued to rise on granitic sites. Reductions in the Annelida and Echinodermata phylum
are not as dramatic and follow trends seen since 2012. In these cases the driver's behind
the reductions is unclear and will be focused on through the monitoring program should
these decreases continue.
The survey list for invertebrates on the 50m belts focuses on commercially important
invertebrates and key species, which indicate ecosystem change. Results from 2013 show
continuation in trends seen in recent years with regards to the Echinoidea phyla with slow
reductions through the years. The most dramatic change is within the corallivorous species,
Drupella snails, where density levels have increased significantly since 2010 reaching a
maximum in 2012, results in 2013 show density has decreased but is still significantly higher
than the other corallivorous invertebrates surveyed. The most likely explanation for the high
numbers of Drupella is that it is coupled with the increase in the branching coral Acropora
spp., their preferred food source and habitat. With continued monitoring it will indicate
whether this population is increasing to damaging levels. Continued monitoring of these
invertebrate species will be critical for identifying the trends and causes for the reduction in
their numbers in recent years.
45
6 Additional Ecosystem Monitoring
6.1. Turtles
Five species of marine turtles are found in Seychelles waters: the leatherback (Dermochelys
coriacea), loggerhead (Caretta caretta), olive ridley (Lepidochelys olivacea), hawksbill
(Eretmochelys imbricata), and green (Chelonia mydas) (IUCN 1996). The leatherback,
loggerhead and olive ridley, although common to parts of the Western Indian Ocean, are not
thought to currently nest in the Seychelles and are rarely seen, especially in the Inner
Islands. However, the hawksbill and green are residents in coastal waters of the Seychelles,
nest on the beaches, and are commonly observed. All five species found in the Seychelles
face the combined threats of poaching, pollution and loss of nesting sites, and are listed by
IUCN as endangered or critically endangered. The Seychelles is considered one of the most
important sites for the critically endangered hawksbill turtle and is one of the only localities in
the world where they can be observed nesting during daylight hours.
GVI staff and volunteers are trained in turtle biology and the identification of the two species
commonly seen around north-west Mahé, C. mydas and E. Imbricata, through lectures and
Power Point presentations. Volunteers are also trained in survey methodology for water
based and land based turtle surveys.
6.1.1. Incidental Turtle Sightings
For every dive undertaken by GVI, a record of turtle observations is kept. The parameters
for each of GVI’s dives are logged, regardless of whether or not a turtle was seen, enabling
the calculation of turtle frequency per dive and thus effort-related abundance. The species,
carapace length, sex, distinguishing features and behaviour of all turtles sighted is recorded
wherever possible.
Incidental sightings of sea turtles are divided into three month periods to more accurately
view the fluctuations that occur in and outside of nesting season. From January to March out
of the 169 boats that went out a total of 59 turtles were sighted. This figure discounts any
turtle behaviour dives, as the focus of these dives is to search for turtles, therefore sightings
are not incidental. Of these sightings, 41 were identified as hawksbill turtles and 18 as green
turtles, which gave an overall sighting frequency of 36.9%. Within the April to June period
following this, 32 turtles were sighted on 126 dives; consisting of 24 hawksbills and 8 green
turtles, giving a lower overall sighting frequency of 25.40% (figure 6.1).
46
Figure 6. 1 Frequency (%) of hawksbill and green turtle sightings around north-westMahé from Oct- Dec 2005 to April-Jun 2013.
In analysing the sightings results the frequency found for the months within October to
December is comparatively higher than for those within July to September; a pattern that can
be observed for hawksbills throughout our recorded data. This increase in encounters in the
Seychelles’ coastal waters during this time can in part be explained by the immigration of
sexually mature turtles to these designated nesting areas (Witzell 1983, Houghton et al. 2003,
Ellis & Balazs 1998). This can be seen by a 100% increase in sighting frequency for adult
hawksbills in October to December. Carapace length can be used as a guide to the stage of
sexual maturity of sea turtles, therefore for every turtle sighting the curved carapace length
(CCL) is estimated. The approximate minimum carapace length of breeding-age female
green and hawksbill turtles is 105cm and 80cm respectively (Mrosovsky 1983). The mean
estimated carapace length for hawksbill turtles during the January to March and April to June
period was 56.80cm (± 2.57 SE) and 49.60cm (± 2.93 SE) respectively (figure 6.2.). This
reveals a general steady population of sexually immature sea turtles. There was only one
recorded sighting of a male during the January-March period, likely due to the influx of adult
females during this time.
0
10
20
30
40
50
60
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Freq
uency of SighL
ng (%
)
Survey Phase
Hawksbill Turtles
Green Turtles
47
Figure 6. 2 Mean carapace length of hawksbill turtles around north-west Mahé from Jan- Mar 2006 to Apr- Jun 2013
6.1.2. Beach Patrols for Nesting Turtles
Beach patrols are conducted on north-west Mahé during the Hawksbill turtle nesting season
from October to March. This land-based turtle monitoring work includes beach walks,
documentation of nesting tracks, and investigation of newly hatched clutches. Beach patrols
are carried out weekly at beaches local to the Cap Ternay research station (Anse du Riz and
Anse Major) to monitor nesting turtle activity. The surveys are conducted on foot, with the
teams searching for signs of tracks or body pits walking along the upper beach, on the main
beach, and also within the coastal vegetation.
Within the January to March period, due to bad weather, only 2 beach patrols were
conducted on both Anse du Riz and Anse Major beach, with no signs of turtle activity during
this time.
6.1.3. In-water Surveys of Turtle Behaviour
In studies concentrating on the home ranges of sea turtles it has been found that normal
daily activities of sea turtles centre around areas of high food availability and resource
quality. When sufficient resources are available, individuals develop affinities for specific
areas (Makowski et al. 2006). Preliminary results from research conducted by Von Brandis in
the Amirantes, Seychelles, established that philopatric behaviour is common among foraging
hawksbill turtles, and extensive information on individuals and their energy budgets can be
gathered using relatively non-invasive sampling protocols (Von Brandis pers. comm.). Focal
behavioural studies work on the philosophy that an individual, when followed and observed
correctly, can provide a wealth of ecological information that would otherwise be unnoticed in
0 10 20 30 40 50 60 70 80
Survey Phase
Mean carapa
ce lengtrh (cm)
48
a simple point count survey. These in water behavioural studies also help to ‘ground truth’
studies done using electronic data such as satellite tagging (Houghton et al. 2003).
Our objective is to document important interactions between hawksbill turtles and their
environment while obtaining information on feeding preferences and the number of
individuals displaying philopatric behaviour within the Baie Ternay Marine Reserve.
Volunteers use SCUBA equipment to undertake a U-shaped search pattern. Divers look for
focal animals and, upon finding an individual, follow and document all behaviours observed.
Environmental conditions can dictate at what distance accurate observations are made
without altering normal behaviour but in general a distance of no closer than 5m is sufficient.
A continuous time scale of data is used; divers stay with any individual encountered for as
long as possible even if another individual is located. In the event that another turtle is found,
the second member of the buddy pair may start to document behaviour but at no time are
buddy pairs to become separated by more than 2m. Any characteristic markings should be
documented and the use of underwater photography is highly desirable for turtle
identification and determining unknown prey items. Due to logistical constraints, it is only
possible for the study in Baie Ternay to be carried out on a weekly basis, incorporating two
45 minute dives with most volunteers participating in one dive; however it is an interesting
addition to the routine for volunteers, enhancing their skill set and appreciation for marine
ecological fieldwork.
Between January to March of 2013 a total of 47 individual buddy pairs completed the
behavioural surveys sighting 12 turtles. Of these 5 were hawksbills and 7 were green. The
mean carapace length (CCL) was 55.45 cm ± 3.78 SD. April to June showed a much higher
sighting frequency with 27 turtles being spotted on 53 individual dives. Interestingly, only 6 of
these were green turtles and 20 being hawksbills, with 1 turtle sighted but not identified to
species level. The mean CCL for this phase was 55.38cm ±3.97 SD. Both phases show
similar mean CCL values, however there is a greater range for the second phase. This is
interesting as we would expect to see a higher sighting frequency of larger turtles during the
first phase as it sits at the end of the nesting season.
Of the turtles sighted,the greatest frequency of sightings occurred within the 0-10m depth
class, with four sightings recorded outside of these depths with 3 at 11m and one at 13.8m.
The shallow reef slope of Baie Ternay Centre does bias the results towards the shallower
depth class, as the 0-10m range covers a larger area of reef and therefore a larger area of
49
foraging grounds. From the studies it was noted that algae and soft coral were all common
chosen food items.
Through the use of photo identification methods, spoken about in the following section, a
number of individual turtles have been seen returning to, or residing within, specific areas of
Baie Ternay Marine Park over a time scale of several months.
It is impossible to correctly determine the specific home range of sea turtles without the use
of remote telemetry, however one or more areas of disproportionately heavy use (i.e. core
areas) can be identified for some of the more frequently spotted turtles. Understanding the
spatial use patterns of sea turtles is fundamental to their conservation. This study reveals
that Baie Ternay remains an important habitat for both the endangered green and hawksbill
turtles; thus, further underscoring the need to develop and maintain conservation strategies
that address the impacts that threaten this region.
6.1.4. Photo Identification of Turtles
Throughout 2012 the use of photo identification methods for turtles was implemented into all
dives where volunteers or staff had an underwater camera. The post-ocular area of scales
on the left and right cheeks of both hawksbill and green turtles are unique to each individual,
allowing for comparisons to be made between identification shots taken on different dives.
Individuals can be recognised through analysis of the photographs, based on a code defined
from the localisation and the number of sides of each scale of the head profile. This method
has been taken from the Kelonia Observatory for Sea Turtles in Reunion Island (Ciccione et
al. n.d.).
The ability to recognise individuals in a population allows for reliable information to be
collected on distribution, habitat use, or life history traits. It is from the increased emphasis
on the importance of photographic identification that resident turtles have been accurately
re-identified, and their home ranges consequently estimated within Baie Ternay marine
national park. A number of individual turtles, both hawksbill and greens, have been
accurately re-identified over varying time scales within the MPA. From data collected from
these sightings it has been noted that many have distinct habitat preferences and feeding
and resting areas. Photo-identification has also been critical in identifying the reasons behind
the low trend in carapace length and any incidence of philopatric behaviour.
50
6.2. Crown of Thorns
Outbreaks of the coral predator, the Crown of Thorns starfish (Acanthaster planci), were first
reported in 1996 and were active until 1998, when the reefs suffered from the bleaching-
induced coral mortality (Engelhardt 2004). Normal density levels are less than one individual
per hectare (Pratchett 2007) and in these numbers A. planci can assist coral diversity by
feeding on the faster growing corals such as Acropora and Pocillopora, which are its
preferred prey items (Pratchett 2007) and early colonisers of degraded reefs that can out-
compete slower growing corals (Veron 2000). In high numbers however the level of
competition for food drives the starfish to eat all species of corals and reefs can become
severely degraded with coral cover reduced to as little as 1% (CRC Reef 2001). The causes
of outbreaks are still not completely understood; it may be connected to overfishing of A.
planci predators, such as the giant triton shell, which is popular with shell collectors, or to
natural fluctuations (CRC Reef2001). The most influential factor could be increased nutrient
levels in the oceans, from agricultural, domestic or industrial sources. A. planci are surveyed
as part of the invertebrate abundance and diversity belts and incidental sightings are also
documented after every dive. There were 111 separaterecordings of A. planci across all
sites during January - June 2013.
6.3. Cetacean Sightings
Cetaceans are considered to be under threat in many parts of the world and in response to
this threat, a national database of cetacean sightings, the Seychelles Marine Mammal
Observatory (SMMO), has been set up. GVI records all incidental cetacean sightings and
passes all data to MCSS for inclusion in the national database. Data recorded includes
date, time, location (including GPS coordinates where possible), environmental conditions,
number of individuals, distinguishing features, size, behaviour and species. There were only
6 separate recordings of dolphin sightings within January to June 2012. Pod sizes ranged
from 5 to 10 individuals and all were sighted from the boat.
6.4. Whale Shark Sightings
The Seychelles is famous for its seasonal fluctuations in the abundance of whale sharks
(Rhincodontypus). However despite their public profile, relatively little is known about their
behaviour or the ecological factors, which influence their migratory patterns. A whale shark
monitoring programme was started in 1996 and is now the cornerstone of an eco-tourism
operation run by MCSS. From 2001-2003, a tagging programme was initiated to study
migratory patterns as part of the Seychelles Marine Ecosystem and Management Project
(SEYMEMP); it is now clear that the sharks seen in the Seychelles are not resident, but
range throughout the Indian Ocean. The oceanographic or biological conditions that
51
determine the movements are unclear, it is possible however that the sharks follow seasonal
variations in the abundance of the plankton on which they feed. All sightings of whale
sharks are documented in as much detail as possible; including time, date, GPS point,
number, size of the individuals, sex, distinguishing features, behaviour and tag numbers if
present. Photographs are also taken whenever possible of the left and right side of the
thorax from the base of the pectoral fin to behind the gill area to be used as identification in
the global and regional database.
Within the January to June 2013 period there were no sightings of whale sharks.
6.5. Plankton Sampling
MCSS initiated a plankton monitoring programme in conjunction with the tagging and
incidental recording surveys in an attempt to correlate the frequency of whale shark sightings
with plankton levels. Plankton sampling has been run by MCSS since 2003 in conjunction
with their on-going monitoring and tagging programmes. GVI started to assist MCSS in the
collection of plankton data in July 2004, and have since carried out the survey on a weekly
basis. Five plankton tows are carried out to the North West side of Grouper Point, just
outside of Baie Ternay, between 08:00 and 11:00 hours. The tows are carried out along a
North Westerly course from Grouper Point. In order to sample over a range of depths the
net is let out 5m every 30 seconds (up to 50m). Samples are collected in the ‘cod end’ of the
net, decanted into a receptacle and preserved in formalin. After the survey and the filtering
process, they are sent to MCSS for measurement of wet weight and species classification.
Environmental conditions are also noted (sea state, cloud cover and turbidity).
Plankton tows were successfully conducted on a weekly basis from January to June when
weather conditions allowed and all samples were sent on to MCSS for analysis.
52
7. Non-‐survey Programmes
7.1 Extra Programmes
7.1.1 Internships
GVI Seychelles currently runs internship programs in conjunction with the marine research
activities. Interns typically spend 8 - 12 weeks with GVI on the marine expedition and then if
the volunteer is participating in the dive master internship a further twelve weeks at a dive
shop in either Seychelles or Thailand gaining the PADI divemaster qualification and
professional dive master experience. Additional courses run through the internships include
a short course on team leadership and/or biological survey techniques. Additional
assignments included written and formal presentations given to the group, along with
management of one day of surveying and one community event where the intern must plan
and run an effective schedule.
7.2 Community Development
7.2.1 Community Education Programmes
The GVI Seychelles community education program works in conjunction with the
International School of the Seychelles (ISS) and the Presidents Village Children's Home.
Lessons and activities are held on a weekly basis within one of the National Marine Parks on
Mahé, either Port Launay or Baie Ternay. Activities include lessons on marine biology and
conservation along with snorkelling and swimming lessons. This aspect of the expedition is
key to the overall impact of our role within the Seychelles. It also increases the extent to
which volunteers are able to contribute on an individual level, to help raise vital awareness of
marine conservation issues related directly to the Seychelles.
7.2.2 GVI Charitable Trust
As part of the GVI Charitable Trust, GVI Seychelles has partnered with the Presidents
Village Children’s Home in Port Glaud. The Presidents Village is part of The Children’s
Home Foundation, which has several children’s homes in the Seychelles. The Presidents
Village provides a home for children who are either orphaned or do not have parents able to
take care of their needs and currently houses approximately 60 children from birth to 18
years old. GVI Seychelles currently is raising funds for the Presidents Village to develop a
renewable energy system by installing solar panels to reduce the overall utilities costs,
enabling them to allocate those funds to be spent on the children, and educate the children
on the benefits of renewable energy sources. GVI volunteers attend weekly snorkel trips to
53
Port Launay Marine Park for the children at Presidents Village. Some of the children are
confident swimmers so were shown some of the fish and corals by the volunteers which they
attempted to identify back on the beach. Other children are new swimmers and the
experience is an introduction to water safety and an appreciation of the marine environment.
These snorkelling trips provide an opportunity for the children to interact with other members
of their local community and spend some time away from the Children’s home in a
structured, educational and fun activity.
7.2.3 National Scholarship Programme
As part of GVI’s local capacity program GVI runs a National Scholarship programme in each
country. The National Scholarship Programme is directly funded by GVI volunteer's
payments and aims to increase long-term capacity building within the country. National
recruits such as rangers, researchers and students are selected by the local partner
organisations and are brought into the programme as volunteers. In order for SNPA to
continue and build upon the research conducted by GVI, scholars are invited to join every
expedition. To date The NSP Programme has been used to train 12 national park rangers
from the SNPA in monitoring conducted by GVI. In the period between January and June
2013, two NSP's from the University of Seychelles Environmental Science undergraduate
course joined the expedition for a four week program as part of their work based experience.
The focus of their studies on the expedition was fish species identification and surveying.
54
8. References Barbault TR (1992) Hétérogénéité spatiale, variabilité, temporelleetpeuplements. In: Ecologie des peuplements: structure, dynamiqueet évolution. Masson, pp 141-163 Bell JD, Galzin R (1984) Influence of live coral cover on a coral reef fish communities. Mar EcolProgSer15 : 265-274 Birkeland C (1977) The importance of rates of biomass accumulation in early successional stages of benthic communities. Proc 3rd Int Coral Reef Symp 1:15–21 Carpenter KE, Miclat RI, Albaladejo VD, Corpuz VT (1981) The influence of substrate structure on the local abundance and diversity of Philippine reef Þshes. Proc 4th Int Coral Reef Symp2 : 497-502 Chabanet, P., Ralambondrainy, H., Amanieu, M., Faure, G. &Galzin, R. (1998) Relationships between coral reef substrata and fish.Coral Reefs. 16. 93-102. Coleman, N. (2000) Marine Life of the Maldives, Atoll Editions, Apollo Bay, Australia Colvocoresses J., Acosta A., (2007), A large scale field comparison of strip transect and stationary point count methods for conducting length-based underwater visual surveys of reef fish populations. Fisheries Research85, 130-141 Ciccione, S., Jean, C., Ballorain, K. &Bourjea, J. (n.d.), Photo-identification of marine turtles: an alternative method to mark-recapture studies, Kelonial’Observatoire des Tortues Marines, Region Reunion. CRC Reef, (2001), Crown-of-thorns starfish on the Great Barrier Reef: Current state of knowledge: April 2001. Coral Reef Research Centre James Cook University, Townsville Ellis, D. M. & Balazs, G. H. (1998) Use of a generic mapping tools program to plot Argos tracking data for sea turtles, in S. P. Epperly and J. Braun (comp.) Proceedings of the 17th Annual Symposium on Sea Turtle Biology and Conservation, NOAA Tech. Memo, NMFS-SEFSC-415, pp. 166–168 Engelhardt U.,( 2001), Interim Report No. 1 (December 2001): Report on scientific field studies and training activities conducted in June / July 2001. Seychelles Marine Ecosystem Management Project.Reefcare International Pty Ltd, Townsville Engelhardt U.M., Russell & WendlingB. (2003), Coral Communities around the Seychelles Islands 1998–2002, p.212 – p.231 Engelhardt U. (2004)The status of scleractinian coral and reef-associated fish communities 6 years after the 1998 mass coral bleaching event. Seychelles Marine Ecosystem Management Project.Global Environment Facility/Government of Seychelles/World Wildlife Fund, Victoria. Ferrier-Page`s, C., Gattuso,J.P., Dallot, S. &Jaubert, J. (2000) Effect of nutrient enrichment on growth and photosynthesis of the zooxanthellate coral Stylophorapistillata. Coral Reefs 19 :pp.103 – 113 Garpe, K.C., Yahya, S.A.S., Lindahl, U. &Ohman M.C. (2006) Longterm effects of the 1998 coral bleaching event on reef fish assemblages. Marine Ecology Progress Series 315:237–247. Gell, F. R., and C. M. Roberts.(2003). Benefits beyond boundaries: the fishery effects of marine reserves. Trends in Ecology and Evolution 18:448–455. Glynn, P.W. (2006) Fish utilization of simulated coral reef frameworks versus eroded rubble substrates off Panama, eastern Pacific. Proceedings of the 10th International Coral Reef Symposium 1:250–256. Graham, N.A.J., Wilson, S.K., Jennings, S., Polunin, N.V.C., Bijoux, J.P., & Robinson, J. (2006) Dynamic fragility of oceanic coral reef ecosystems, PNAS, 103, no. 22 Graham N. A. J., Wilson S. K., Jennings S., Polunin N. V. C., Robinson J., Bijoux J. P., Daw T. M., (2007), Lag Effects in the Impacts of Mass Coral Bleaching on Coral Reef Fish, Fisheries, and Ecosystems. Conservation Biology 21(Issue 5), 1291-1300 Grimsditch, G.D. &Salm, R.V. (2006).Coral Reef Resilience and Resistance to Bleaching.IUCN, Gland, Switzerland. 52pp. Halpern, B. S. (2003). The impact of marine reserves: Do reserves work and does size matter? Ecological Applications 13:S117–S137. Hill J., Wilkinson C., (2004), Methods for Ecological Monitoring of Coral Reefs: Version 1. A Resource for Managers.Australian Institute of Marine Science, Townsville. Houghton, J.D.R., Callow, M.J. & Hays, G.C. (2003) Habitat utilization by juvenile hawksbill turtles (Eretmochelys imbricata, Linnaeus, 1766) around a shallow water coral reef, Journal of Natural History, 37, pp. 1269–1280 Hughes, T.P., (1994), Catastrophes, phase shifts and large scale degradation of a coral reef, Science 256, pp. 1547-1551
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IUCN (1996), A Marine Turtle Conservation Strategy and Action Plan for the Western Indian Ocean. International Union for Conservation of Nature and Natural Resources. Jennings S., Boulle D. P., Polunin N. V. C., (1995), Habitat correlates of the distribution and biomass of Seychelles reef fishes. Environmental Biology of Fishes 46, 15-25 Jompa J, McCook (2002a) Effects of competition and herbivory on interactions between a hard coral and a brown alga. J Exp Mar BiolEcol 271:25–39 Jompa J, McCook (2002b) The effects of nutrients and herbivory on competition between a hard coral (Poritescylindrica) and a brown alga (Lobophora variegata). Limnol Oceanogr 47:527–538 Klumpp DW, McKinnon AD (1989) Temporal and spatial patterns in the primary production of a coral reef epilithic algal community. J Exp Mar BiolEcol 131:1–22 Kulbicki M., (1998), How the acquired behavior of commercial reef fishes may influence the results obtained from visual censuses. Journal of Experimental Marine Biology and Ecology 222, 11-30 Leujak W., Ormond R.F.G.,(2007), Comparative accuracy and efficiency of six coral community survey methods. Journal of Experimental Marine Biology and Ecology351, 168-187. Lindèn, O., Souter, D., Wilhelmsson, D. &Obura, D. (2002), Coral Reef Degradation in the Indian Ocean, CORDIO, Kalmar, Makowski, C., Seminoff, J.A. & Salmon, M. (2006). Home range and habitat use of juvenile Atlantic green turtles (Cheloniamydas L.) on shallow reef habitats in Palm Beach, Florida, USA. Marine Biology. 128. 1167-1179. McClanahan, T.R., Baird, A.H., Marshall &Toscano, M.A. (2004) Comparing bleaching and mortality responses of hard corals between southern Kenya and the Great Barrier Reef, Australia. Marine Pollution Bulletin 48: 327 – 335. Micheli, F. & Halpern, S. (2005) Low functional redundancy in coastal marine assemblages.Ecology Letters. 8. 391-400. Mrosovsky, N., (1983). Conserving Sea Turtles. The British Herpetological Society, London, p. 4 Nugues, M. & Roberts, C. (2003) Partial mortality in massive reef corals as an indicator of sediment stress on coral reefs, Marine Pollution Bulletin,46, 314– 323 Pratchett M.S., (2007), Feeding preferences of Acanthasterplanci (Echinodermata: Asteroidea) under controlled conditions of food availability.Pacific Science 61 (Issue 1), 113-120 Samoilys M., Gribble N., (1997), Manual for Assessing Fish Stocks on Pacific Coral Reefs.Queensland Training Series.Department of Primary Industries, Brisbane. Sano M, Shimizu M, Nose Y (1984) Changes in structure of coral reef fish communities by destruction of hermatypic corals: observational and experimental views. Pac Sci 38 (1) : 51-79 Sluka, R. D. & Miller, M. W. (2001) Herbivorous Fish Assemblages and Herbivory Pressure on Laamu Atoll, Republic of Maldives. Coral Reefs, 20. Pp. 255-262 Sobel, J. A., and C. P. Dahlgren. (2004). Marine reserves. A guide to science, design and use. Island Press, Washington D.C., USA. Spalding M. D., Jarvis G. E., (2002), The impact of the 1998 coral mortality on reef fish communities in the Seychelles. Marine Pollution Bulletin 44, 309-321 Steneck RS (1988) Herbivory on coral reefs: a synthesis. Proc 6th Int Coral Reef Symp 1:37–49 Turner, J., Klaus, R. &Engelhardt, U. (2002)The reefs of the granitic islands of the Seychelles, CORDIO Veron, J.E.N., (2000) Corals of the World, Australian Institute of Marine Science, Townsville, Australia, Vol1–3 Ward, S. & Harrison, P. (2000) Changes in gametogenesis and fecundity of acroporid corals that were exposed to elevated nitrogen and phosphorus during the ENCORE experiment. J Exp Mar BiolEcol246 : 179 – 221 Witzell, W. (1983) Synopsis of biological data on the hawksbill turtle, Eretmochelysimbricata (Linnaeus, 1766), FAO Fish, Synop., pp. 137
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9. Appendices
Appendix A.Details of sites surveyed by GVI Seychelles – Mahé, year round. Sites in
bold-type text are located within Marine Protected Areas.
Site
No Site Name GPS
Survey
Status Granitic/Carbonate
1 Conception North Point S 04°39.583, E 055°21.654 Core Granitic
2 Conception Central East Face S 04°39.891, E 055° 22.258 Core Carbonate
4 Port Launay West Rocks S 04º39.416, E 055º23.382 Core Granitic
5 Port Launay South Reef S 04º39.158, E 055º23.695’ Core Carbonate
7 BaieTernay Lighthouse S 04°38.373, E 055°21.993 Core Granitic
8 BaieTernay Reef North East S 04°38.013, E 055°22.405 Core Granitic
9 BaieTernay Reef Centre S 04°38.321, E 055°22.504 Core Carbonate
10 BaieTernay Reef North West S 04°38.382, E 055°22.133 Core Carbonate
11 Ray’s Point S 04°37.347, E 055°23.145 Core Granitic
12 A Willie’s Bay Reef S 04°37.650, E 055°22.889 Core Carbonate
12 B Willie’s Bay Point S 04°37.589, E 055°22.776 Core Granitic
13 A Anse Major Reef S 04°37.546, E 055°23.121 Core Carbonate
13 B Anse Major Point S 04°37.509, E 055°23.010 Core Granitic
14 Whale Rock S 04°37.184, E 055°23.424 Core Granitic
15 Auberge Reef S 04°37.024, E 055°24.243 Core Carbonate
16 Corsaire Reef S 04°37.016, E 055°24.447 Core Carbonate
17 White Villa Reef S 04º36.935, E 055º24.749 Core Carbonate
18 L’ilot North Face S 04°38.652, E 055°25.932 Core Granitic
19 Site Y S 04°37.771, E 055°22.660 Core Granitic
21 Therese North End S 04°40.101, E 055°23.737 Core Granitic
22 Therese North East S 04°40.099, E 055°23.891 Core Carbonate
23 Therese South S 04°40.764, E 055°24.310 Core Granitic
24 Site X S 04°37.059, E 055°23.783 Core Granitic
N/A Secret Beach Reef N/A Core Carbonate
57
Appendix B.Scleractinian coral genera surveyed by GVI Seychelles - Mahé.
Acroporidae
Acropora
Fungiidae
Fungia
Astreopora Herpolitha
Montipora Diaseris
Pocilloporidae
Pocillopora Cycloseris
Stylophora Podabacia
Seriatopora Halomitra
Poritidae
Porites Polyphyllia
Goniopora
Faviidae
Favia
Alveopora Favites
Dendrophylliidae Turbinaria Montastrea
Siderastreidae
Siderastrea Plesiastrea
Pseudosiderastrea Goniastrea
Coscinaraea Echinopora
Psammocora Diploastrea
Mussidae
Lobophyllia Leptasrea
Symphyllia Cyphastrea
Acanthastrea Platygyra
Blastomussa Leptoria
Oculinidae Galaxea Oulophyllia
Euphyllidae Physogyra Astrocoeniidae Stylocoeniella
Pectinidae
Pectinia
Agaricidae
Pavona
Mycedium Leptoseris
Echinophyllia Gardineroseris
Merulinidae Merulina Coeloseris
Hydnophora Pachyseris
58
Appendix C.Fish families, genera and species surveyed by GVI Seychelles - Mahé.
Family Scientific name Common name Feeding guild
Relevance
(Engelhardt
2004)
Butterflyfish
(Chaetodontidae)
Chaetodonvagabundus Vagabond C/I Coral recovery
Chaetodonauriga Threadfin C/I Coral recovery
Chaetodontrifascialis Chevroned C Coral recovery
Chaetodonmelannotus Black-backed C/I Coral recovery
Chaetodonmertensii Merten's C/I Coral recovery
Chaetodontriangulum Triangular C Coral recovery
Chaetodontrifasciatus Indian Redfin C Coral recovery
Chaetodoninterruptus Indian Ocean Teardrop C/I Coral recovery
Chaetodonbennetti Bennett's C Coral recovery
Chaetodonlunula Raccoon C/I Coral recovery
Chaetodonkleinii Klein's C/I Coral recovery
Chaetodoncitrinellus Speckled C/I Coral recovery
Chaetodonguttatisimus Spotted C/I Coral recovery
Chaetodonlineolatus Lined C/I Coral recovery
Chaetodonfalcula Saddleback C/I Coral recovery
Chaetodonmeyersi Meyer's C Coral recovery
Chaetodonxanthocephal
us Yellow-headed C/I Coral recovery
Chaetodonzanzibariensis Zanzibar C Coral recovery
Forcipiger sp. Longnose sp. C/I Coral recovery
Angelfish
(Pomacanthidae)
Apolemichthystrimaculat
us Three-spot V Visual appeal
Pomacanthus imperator Emperor V Visual appeal
Pomacanthussemicircula
tus Semicircle V Visual appeal
Pygoplitesdiacanthus Regal V Visual appeal
Surgeonfish
(Acanthuridae)
Acanthurus sp. Surgeonfish H Algae vs. coral
Ctenochaetus sp. Bristletooths H Algae vs. coral
Naso sp. Unicornfish Pl Algae vs. coral
Zancluscornutus Moorish idol V Visual appeal
Rabbitfish (Siganidae)
Siganuspuelloides Blackeye H Algae vs. coral
Siganuscorallinus Coral H Algae vs. coral
Siganusstellatus Honeycomb H Algae vs. coral
Siganusargenteus Forktail H Algae vs. coral
59
Siganussutor African Whitespotted H Algae vs. coral
Snappers (Lutjanidae)
Lutjanusgibbus Paddletail Pi Fishing pressure
Lutjanussebae Red emperor Pi Fishing pressure
Lutjanusfulviflamma Longspot Pi Fishing pressure
Lutjanuskasmira Blue-lined Pi Fishing pressure
Lutjanusbengalensis Bengal Pi Fishing pressure
Lutjanusmonostigma Onespot Pi Fishing pressure
Lutjanusvitta Brownstripe Pi Fishing pressure
Lutjanusfulvus Flametail Pi Fishing pressure
Lutjanusargentimaculatu
s Mangrove jack Pi Fishing pressure
Lutjanusbohar Red Pi Fishing pressure
Lutjanusrusselli Russell's Pi Fishing pressure
Macolorniger Black Pi Fishing pressure
Aprionvirescens Green jobfish Pi Fishing pressure
Triggerfish
(Balistidae)
Balistoidesviridescens Titan I Sea urchins & COTs
Sufflamenchrysopterus Flagtail I Sea urchins & COTs
Balistidae Other triggerfish I Sea urchins & COTs
Emperors
(Lethrinidae)
Monotaxis sp. Redfin/Bigeye bream I Sea urchins & COTs
Gymnocraniusgrandoculi
s
Blue-lined large-eye
bream I Sea urchins & COTs
Lethrinusolivaceous Longnosed I Sea urchins & COTs
Lethrinusnebulosus Blue-scaled I Sea urchins & COTs
Lethrinusrubrioperculatus Redear I Sea urchins & COTs
Lethrinusxanthochilus Yellowlip I Sea urchins & COTs
Lethrinusharak Thumbprint I Sea urchins & COTs
Lethrinuslentjan Pinkear I Sea urchins & COTs
Lethrinusobsoletus Orange-striped I Sea urchins & COTs
Lethrinuserythracanthus Yellowfin I Sea urchins & COTs
Lethrinusmahsena Mahsena I Sea urchins & COTs
Lethrinusvariegatus Variegated I Sea urchins & COTs
Groupers
(Serranidae)
Anyperodonleucogrammi
cus Slender Pi Fishing pressure
Cephalopholisargus Peacock Pi Fishing pressure
Cephalopholisurodeta Flagtail Pi Fishing pressure
Cephalopholisminiata Coral Hind Pi Fishing pressure
Cephalopholissonnerati Tomato Pi Fishing pressure
Epinephelusmerra Honeycomb Pi Fishing pressure
60
Epinephelusspilotoceps Foursaddle Pi Fishing pressure
Epinepheluspolyphekadi
on Camouflage Pi Fishing pressure
Epinepheluscaeruleopun
ctatus Whitespotted Pi Fishing pressure
Epinephelusfuscoguttatu
s Brown-marbled Pi Fishing pressure
Epinephelustukula Potato Pi Fishing pressure
Epinephelusfasciatus Blacktip Pi Fishing pressure
Aethalopercarogaa Redmouth Pi Fishing pressure
Variolalouti Yellow-edged Lyretail Pi Fishing pressure
Plectropomuslaevis Saddleback Pi Fishing pressure
Plectropomuspunctatus African Coral Cod Pi Fishing pressure
Sweetlips
(Haemulidae)
Plectorhinchusorientalis Oriental I Sea urchins & COTs
Plectorhinchuspicus Spotted I Sea urchins & COTs
Plectorhinchusgibbosus Gibbus I Sea urchins & COTs
Parrotfish
(Scaridae)
Bolbometoponmuricatum Bumphead parrotfish C/H Coral damage
Scaridae Other parrotfish H Algae vs. coral
Wrasse (Labridae)
Cheilinustrilobatus Tripletail I Sea urchins & COTs
Cheilinusfasciatus Redbreasted I Sea urchins & COTs
Oxycheilinusdigrammus Cheeklinedsplendour I Sea urchins & COTs
Cheilinusundulatus Humphead I Sea urchins & COTs
Tetraodontidae Puffers I Sea urchins & COTs
Diodontidae Porcupinefish I Sea urchins & COTs
Holocentridae
Soldierfish Pl Upwelling areas
Squirrelfish Pl Upwelling areas
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Appendix D. Fish feeding guilds analysed by GVI Seychelles – Mahé.
Code Feeding guild Description (adapted from Obura and Grimsditch, 2009) Key species
Pl Planktivores Resident on reef surfaces, but feed in the water column. Their abundance is related to quality of reef habitat for
refuge, and water column conditions.
Soldierfish, Squirrelfish, Unicornfish
Pi Piscivores
High level predators. Exert top-down control on lower trophic levels. Important fisheries species but very
vulnerable to overfishing thus good indicators of the fishing pressure on a reef.
Groupers, Snappers
C Corallivores Relative abundance is an indicator of coral community health
Butterflyfish (Chevroned,
Triangular, Bennetts, Indian Redfin,
Meyers, Longnose sp.)
V Varied diet Feed on coral competitors such as soft corals and
sponges. Relative abundances may be an indicator of abundance of these prey items and of a phase shift.
Angelfish, Moorish Idol
I Invertivores*
Second-level predators with highly mixed diets including small fish, invertebrates and dead animals. Important
fisheries species thus abundances are a good indicator of fishing pressure.
Sweetlips, Emperors, Pufferfish,
Porcupinefish, Wrasse (Tripletail,
Redbreasted, CheeklinedSplendor,
Humphead), Triggerfish (Titan,
Flagtail, Other)
H Herbivores
Exert the primary control on coral-algal dynamics. Parrotfish, Surgeonfish, Bristletooth, Rabbitfish
May indicate phase shift from coral to algal dominance in response to mass coral mortality or pressures such as
eutrophication.
C/H Corallivore/Herbivore Relative abundance is a secondary indicator of coral community health Bumphead parrotfish
C/I Corallivore/Invertivore Relative abundance can be a secondary indicator of coral community health
Butterflyfish (Vagabond, Threadfin,
Blackbacked, Mertens, Indian
Ocean Teardrop, Racoon, Kleins,
Speckled, Spotted, Lined, Saddleback,
Yellow headed, Zanzibar)
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Appendix E.Fish species lists divided into commercial and reef species analysed by GVI
Seychelles – Mahé.
Commercial Fish Species Reef Fish Species Siganidae (Rabbitfish) Chaetodontidae (Butterflyfish) Lutjanidae (Snappers) Pomacanthidae (Angelfish) Lethrinidae (Emperors) Acanthuridae (Surgeonfish) Serranidae (Groupers) Balistidae (Triggerfish) Haemulidae (Sweetlips) Labridae (Wrasse) Scaridae (Parrotfish) Tetradontidae (Pufferfish) Diodontidae (Porcupinefish) Holocentridae (Soldierfish& Squirrelfish)
Zancluscornutus (Moorish Idol) Bolbometoponmuricatum(Bumphead Parrotfish)
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Appendix F.List of invertebratespecies surveyed on 50m belt transects by GVI Seychelles
– Mahé.
Mollusca (Gastropoda) Drupella spp. Drupella
Mollusca (Bivalvia) Tridacnidae Giant Clam
Sea Stars (Asteroidea)
Culcita spp. Cushion Sea Star
Acanthasterplanci Crown of Thorns Sea Star
Other Sea Stars
Sea Urchins (Echinoidea)
Diadema spp. Long Spine Urchin
Echinometra spp. Mathae’s Urchin
Echinothrix spp. Short Spine Urchin
Pencil Urchin
Toxopneustespileolus Flower Urchin
Cake Urchin
Sea Cucumbers (Holothuroidea)
Holothuriaartra Lollyfish
Holothuriafuscopunctata Elephant Trunk
Holothuriafuscogilva White teatfish
Holothurianobilis Black teatfish
Holothuria sp.(undescribed) Pentard
Bohadschia spp. Bohadschia
Actinopyga spp. Actinopyga
Actinopygamauritiana Yellow Surfish
Stichopus spp. Stichopus
Thelenotaananas Prickly Redfish
Pearsonothuriangraeffei Flowerfish
Thelenotaanax Royal
Holothuriaedulis Edible Sea Cucumber
(Cephalopoda) Octopus spp. Common Reef Octopus
Lobsters (Palinura) Panulirus spp. Spiny Lobster
Parribacus spp./Scyllarides spp. Slipper Lobster
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Appendix G.Invertebrates surveyed on 10m LIT transects by GVI Seychelles – Mahé.
Annelida (Polychaeta)
Sabellidae Feather Duster worms
Serpulidae Christmas Tree worms
Terebellidae Spaghetti worms
(Platyhelminthes) Polycladida Flatworms
Arthropoda (Crustacea)
Caridea Shrimps
Stomatopoda Mantis shrimps
- Crabs
Mollusca (Gastropoda)
Muricidae Murex
Drupella sp. Drupella
Strombidae Conch
Cypraeidae Cowrie
Ranellidae Triton
Conidae Cone
Trochidae Top
Cassidae Helmet
- Other shells
Nudibranchia Nudibranchs
Mollusca (Bivalvia) Ostreidae Oysters
Tridacnidae Giant Clam
Mollusca (Cephalopoda) Sepoidea Cuttlefish
Teuthoidea Squid
Sea Stars (Asteroidea)
Culcita sp. Cushion Sea Star
Acanthasterplanci Crown of Thorns Sea Star
Other Sea Stars
Ophiuroidea Brittle Stars
Crinoidea Feather Stars
Sea Urchins (Echinoidea)
Diadema sp. Long Spine Urchin
Echinometra sp. Mathae’s Urchin
Echinothrix sp. Short Spine Urchin
Pencil Urchin
Toxopneustes sp. Flower Urchin
Cake Urchin
Other Urchins