draft application to the australian government department ... · species is the blue swimmer crab...

DRAFT APPLICATION TO THE AUSTRALIAN GOVERNMENT DEPARTMENT OF

ENVIRONMENT AND HERITAGE ON THE

NORTHERN DEVELOPMENTAL BLUE SWIMMER CRAB FISHERY

AGAINST THE

Guidelines for the Ecologically Sustainable Management of Fisheries

For Consideration Under Parts 13 and 13A of the Environment

Protection and Biodiversity Conservation Act 1999

NOVEMBER 2005

COMPILED BY

DEPARTMENT OF FISHERIES, WESTERN AUSTRALIA LOCKED BAG 39, CLOISTERS SQUARE WA 6850

Department of Fisheries, Western Australia i

TABLE OF CONTENTS

EXECUTIVE SUMMARY iii

ABBREVIATIONS iv

1. BACKGROUND 1

1.1 Introduction to the fishery 1

1.2 Target species 2

1.3 By-product 2

1.4 Non retained species 2

1.5 Operating description 3

1.6 Catch statistics 4

1.7 Life history 6

2. MANAGEMENT ARRANGEMENTS 9

2.1 Context of current management regime 9

2.2 Description of current management regime 9

2.3 Availability of documented management arrangements 11

2.4 Consultative process for developing management regime 11

2.5 Expertise and community involvement in management of the fishery 12

2.6 The management regime 12

2.7 Controls 14

2.8 Enforcement of management arrangements 14

2.9 Review and performance reporting 16

2.10 Assessment of any adverse impacts of the fishery on the marine ecosystem 17

3. METHODOLOGY 18

3.1 Overview 18

3.2 Workshop 18

3.3 Issue and risk identification and categorisation 19

4. ESD ASSESSMENT 21

PRINCIPLE 1 21

4.1 Objective 1 21

4.1.1 Information requirements 22

4.1.2-5 Assessment 23

4.1.6-9 Management responses 27

Department of Fisheries, Western Australia ii

4.2 Objective 2 29

PRINCIPAL 2 29

4.3 Objective 1 29



4.4 Objective 2 35




4.5 Objective 3 37


4.5.2 Assessment 38


5. REFERENCES 42

6. APPENDICES 43

Appendix A 44

Appendix B 47

Appendix C 54

Department of Fisheries, Western Australia iii

EXECUTIVE SUMMARY

The collection of blue swimmer crabs from the Northern Developmental Blue Swimmer Crab

Fishery (NDBSCF) is assessed against the Commonwealth Guidelines for the Ecologically

Sustainable Management of Fisheries as required under Parts 13 and 13A of the Environment

Protection and Biodiversity Conservation Act 1999.

The NDBSCF is an experimental fishery that has been in operation since 2001. The target

species is the blue swimmer crab (Portunus pelagicus) though the fishery is also permitted to

take coral crabs (Charybdis cruciata) and sand crabs (Ovalipes australiensis). The method of

fishing is highly selective and few other species are caught as bycatch. The method of fishing

also limits the possibility of interactions with protected species and minimises habitat

disturbance.

Two commercial fishers are authorised to operate in the NDBSCF. Management is by the

Department of Fisheries Western Australia through the Fish Resources Management Act 1994

and Exemption conditions. Precautionary strategies for management of the fishery include

limited entry, species restriction, equipment restrictions, spatial restrictions and limitations

based on biological attributes.

The management regime for the NDBSCF is assessed and it is proposed that the collection of

blue swimmer crabs from this Fishery meets the Guidelines for the Ecologically Sustainable

Management of Fisheries. Detailed justification for this conclusion is documented within this

report.

Department of Fisheries, Western Australia iv

ABBREVIATIONS CAES Catch and Effort Statistics CALM Department of Conservation and Land Management CPUE Catch per unit effort CW Carapace width DEH Department of the Environment and Heritage DFWA Department of Fisheries Western Australia EPA WA Environmental Protection Authority EPBC Environmental Protection and Biodiversity Conservation Act, 1999 ESD Ecologically Sustainable Development FBL Fishing Boat Licence FRDC Fisheries Research and Development Corporation FRMA Fish Resources Management Act, 1994 FRMR Fish Resources Management Regulations, 1995 NDBSCF Northern Developmental Blue Swimmer Crab Fishery SBECF Shark Bay Experimental Crab Fishery WA Western Australia

Department of Fisheries, Western Australia 1

1 BACKGROUND

1.1 Introduction to the fishery

The Northern Developmental Blue Swimmer Crab Fishery (NDBSCF) is an

experimental fishery that has been in operation since 2001. The fishery occupies the

waters between the shore and the 200 m isobath between 115°E latitude and 120°E

latitude, approximately Onslow to Port Hedland on the north-west Western Australian

(WA) coast in the Pilbara region (Fig 1). The area is remote but certain locations,

such as Nickol Bay, are popular with recreational users, resulting in occasional

conflict between recreational and commercial fishers. To minimise potential conflict,

the area is spatially zoned, excluding commercial fishers from fishing within defined

inshore boundaries. There are currently only two commercial blue swimmer crab

fishers operating in the region. The authorisation to operate is issued by way of

Exemption (see Section 2.2).

Figure 1. Location of the NDBSCF.


1.2 Target species The target species of the fishery is the blue swimmer crab (Portunus pelagicus). This

is an Indo-West Pacific species of crab which is found along the WA coast from

Albany on the south coast, north along the whole coastline to the Northern Territory.

Commercially fished stocks are found in the area between Bunbury and Mandurah, the

Peel/Harvey Estuary, Comet Bay (near Mandurah), Warnbro Sound, Cockburn Sound,

the Swan/Canning Estuary, Shark Bay, Exmouth Gulf and Nickol Bay.

In general, blue swimmer crabs are resilient to overfishing due to their short life span,

rapid growth and high fecundity. Size at sexual maturity for blue swimmer crabs is

less than 100mm carapace width (CW) (Melville-Smith et al., 2001).

Differential size limits, in place throughout the State, have been set as a resource

sharing initiative to provide a buffer between the recreational and commercial sectors

and as a mechanism to protect broodstock. In the NDBSCF, recreational minimum

size limits for blue swimmer crabs are set at the precautionary 127mm CW while

commercial minimum legal size limits are set at 135mm CW.

1.3 By-product The NDBSCF is permitted to take coral crabs (Charybdis cruciata). Coral crabs are

generally found in marine coastal waters on a range of bottom types including mud,

sand, rock and seagrasses in depths of up to 60m (Jones and Morgan, 2002). Sand

crabs (Ovalipes australiensis) may also be taken as a by-product. Sand crabs are

distributed across southern Australia. They are common on surf beaches, sandy bays,

and inlets and occur offshore to depths of 100m (Jones and Morgan, 2002). Coral and

sand crabs are not primary targets of the blue swimmer crab fishery and, although they

can be taken as by-product, only small catches of coral crabs and no sand crabs have

been recorded in the NDBSCF.

1.4 Non retained species Few species compromise the bycatch with little bycatch overall (Section 4.3). The

selective method of fishing used in the NDBSCF (Section 1.5) limits both the

possibility of bycatch and interactions with protected species while also minimising

habitat disturbance. There are no programs to quantify bycatch.


1.5 Operating description The NDBSCF uses purpose-designed crab traps (Figs 2 & 3). Generally the traps

consist of two halves, or rings, of up to 1.16m in diameter. The bottom half is a

weighted ring designed to keep the traps on the ocean floor while the upper half is a

buoyant ring constructed of plastic tubing. The buoyant ring, while not having enough

buoyancy to lift the trap off the ocean floor, stretches the mesh upwards to a maximum

height of 0.45m, forming an hourglass shape with a sloping surface towards the

middle of the trap. The two halves are covered in mesh (50 to 90mm) and connected

with cable ties to complete the trap, leaving elongated gaps around the middle, suitable

for the entry of crabs. There is a hole in the top of the trap (i.e. in the middle of the

buoyant ring) that is closed with a pull string while the trap is in the water and is

released on the boat so that the catch can be easily released from the trap. Innovations

in trap design have basically eliminated the catch of juvenile crabs (< 80mm CW) and

greatly reduced the catch of undersized adults of < ~120mm CW. In addition, tag and

recapture data indicate that returned undersize crabs have a high rate of survival

(Melville-Smith et al., 2001). The Research Division of the Department of Fisheries

must approve all trap designs prior to use within the fishery.

Figures 2 & 3. Operators in the NDBSCF using purpose designed crab traps.


1.6 Catch statistics Exemptions for the NDBSCF were first granted in 2001. In 2001, in its first year of

operation, the fishery took 9.9 tonnes (t) over 126 fishing days. Since then

commercial landings of blue swimmer crab in the NDBSCF have risen (64.2t over 366

fishing days in 2003) (Fig 4). In 2004, the total collection by the crab fishery was

49.1t over 160 fishing days.

Fishing effort, measured by the number of pot lifts has significantly increased in the

first three years of the fishery, rising from 19,200 trap lifts in 2001 to 68,500 in 2003.

The number of trap lifts declined in 2004 to 30,700 due to inclement weather

conditions.

Catch per unit effort (CPUE) increased in the NDBSCF from 0.5kg/trap lift in 2001 to

0.9kg/trap lift in 2003 and to 1.8kg/trap lift in 2004 (Fig 4). While total annual catch is

an indicator of stock abundance, CPUE is considered to be the most effective method

of measuring variation in stock abundance and breeding stock levels over the years.

Sustainability of catch levels is also based on the limited extent of the fishery versus a

wide distribution of the species and therefore comprises minimal risk to stock.

As the NDBSCF is still in the exploratory phase, CPUE and total catch are likely to

fluctuate and possibly rise as fishing effort in the area increases and as the level of

local knowledge of fish stocks by the two operators improves.

The increase in CPUE seen in the NDBSCF between 2001 and 2004 (Fig 4) most

likely reflects a refinement of area the sourcing of stock, this is likely to be associated

with the fishers’ increasing knowledge of local stock distribution.

Monthly catch data from the NDBSCF have indicated that catch rates are highest

between May and August with less fishing undertaken in summer due to unfavourable

weather conditions (high daily air temperatures).


0

10

20

30

40

50

60

70

2001 2002 2003 20040

0.5

1

1.5

2

Total catch (tonnes)

CPUE (kg/trap lift)Cat

ch (t

)

CP

UE

(Kg/

trap

lift)

Figure 4. Catch (t) and CPUE for the NDBSCF from 2001-2004. The NDBSCF presently accounts for less than 6 percent of the annual State wide

commercial blue swimmer crab catch (2004)(Fig 5).

012345678

2001 2002 2003 2004

Pro

porti

on (%

)

Figure 5. Proportion (%) of State wide commercial catch caught in NDBSCF from

2001 – 2004

A survey of recreational crabbing in the region estimated a blue swimmer crab catch

of 20 t for the 1999-2000 calendar year, most of which was caught from Nickol Bay

by boat based fishers using scoop nets or diving equipment (Williamson et al., 2005).

Recreational crabbing continues to be of high popularity in the region, however no

additional surveys have been undertaken to date. The needs of the community and the

impact of recreational crabbing have been factored into the commercial management


strategy for the NDBSCF. This has occurred through implementing the differential

size limits, restricting areas in the fishery for recreational crabbing only and by

consulting with the Regional Recreational Fishing Advisory Committee (RRFAC) on

management issues.

1.7 Life history of target species

The time for a complete reproductive cycle among blue swimmer crabs fluctuates

according to annual temperature variations. Spawning takes place all year round in

tropical and subtropical waters, while reproduction in temperate regions is restricted to

the warmer months (Campbell and Fielder, 1986; Ingles and Braum, 1989).

In temperate regions mating occurs in summer, following spawning during the late

summer moult of the female and using sperm from the previous year's mating.

Breeding pairs are formed and mature males, which moult some weeks before

females, each carries a female clasped beneath him for 4-10 days before she moults.

Mating occurs immediately after the female has moulted and when the shell is still

soft. Males can mate with a number of females during the season. Females mate only

once a year but receive enough sperm to fertilise millions of eggs.

Rhythmic egg production based on annual climatic/environmental cues determines the

timing of egg production and spawning. In temperate areas, after mating, the sperm

are retained by the female in spermatheca over the winter (Smith, 1982) until the

temperatures rise again (November to January) and ovule maturation is completed.

Van Engel (1958) found that sperm in the spermathecum of female Callinectes

sapidus could remain viable for at least 12 months.

When the female is ready to deposit her eggs she settles into the sand with her

abdomen extended. The eggs are extruded and attached to hairs on the female’s

abdomen. Some sperm from the sperm capsule are released and fertilisation takes

place externally. The female incubates the eggs under the abdominal flap. They are

bright orange when first spawned and change progressively to dark grey as they

develop and use up the yolk. Small grey remnants of the egg mass may remain for a

short period after the developing eggs have been released into the water (Potter et al.,


1983). Female crabs spawn up to two million eggs per batch, larger crabs producing

more eggs than smaller crabs. The speed of development depends on water

temperature. At 25oC it takes 8 days for the eggs to become fully developed and ready

for release and at 20oC it takes 18 days (Smith, 1982).

In tropical regions, such as the NDBSCF, ovigerous females can be found year round

with a peak in spawning evident in the spring months.

Twenty-four hours before spawning, there is a marked change in activity. The female

remains on the substrate even during daylight hours and continually moves around.

The eggs are released sometime between midnight and dawn, and the female remains

inactive for some hours after spawning has been completed. During this time, she

cleans the remnants of the egg capsules from the pleopodal setae and within four hours

of spawning, all traces of the old egg cases have been removed.

The eggs and larvae of blue swimmer crabs are planktonic. The eggs hatch after about

15 days at 24oC, with the larval phase lasting between 26 to 45 days. The released

larvae spend up to six weeks in coastal waters as far as 80 km out to sea, being mixed

and distributed by the prevailing currents before settling inshore and immigrating into

estuaries in the spring and summer. This transport is facilitated by changes in the

diurnal behaviour of larvae (Meagher, 1971). Meagher (1971) suggests that the

transition in distribution from an offshore, semi planktonic habitat to the onshore,

benthic habitat occurs in juveniles somewhere between 0.4 cm and 1.0 cm carapace

width.

Rapid growth occurs in the estuaries and protected bays over summer. Juveniles and

adults migrate out into the ocean during winter to avoid the freshwater flow (Potter et

al., 1983) and many then migrate back into the estuaries before the summer.

Maturity occurs at about one year of age (Smith, 1982) but size at maturity can vary

with latitude or location and within individuals at any location. In a Western

Australian study the carapace width of the smallest crab found to have reached sexual

maturity i.e. undergone its pubertal moult, ranged from 61 mm in both Peel-Harvey

Estuary and Shark Bay to 90 mm in Leschenault Estuary. The average size at which


females reached sexual maturity in Shark Bay was 92mm CW (Potter et al., 2001).

There has been no specific research on sexual maturity of female crabs in the

NDBSCF, but the geographical characteristics of the region, crab distribution and

water temperature are similar to Shark Bay and size at sexual maturity is expected to

be comparable. In view of this, a conservative estimation of female size at sexual

maturity is 100mm CW.

Large gaps exist in the knowledge and quantification of natural and fishing mortality

in blue swimmer crabs in Australia. High mortality rates are observed in larval crabs

and it has been estimated there is greater than 99% mortality from hatching to the

fourth zoeal stage in South Australia (Bryars, 1997). Research indicates that most

crabs have died, either via natural mortality or fishing by the time they reach 20

months old (Potter et al. 2001).


2. MANAGEMENT 2.1 Context of current management regime

Fisheries management of the NDBSCF is currently administered by the Department

of Fisheries WA (DFWA) under the Fish Resources Management Act 1994 (the

FRMA). The FRMA sets out the objectives for the sustainable management of living

marine resources (as defined as “fish”) and provides the framework for developing

and implementing management arrangements. Objectives of the FRMA are to

conserve, develop and share the fish resources of the State for the benefit of present

and future generations. The specific objects are of the FRMA are:

(a) to conserve fish and to protect their environment;

(b) to ensure that the exploitation of fish resources is carried out in a sustainable

manner;

(c) to enable the management of fishing, aquaculture and associated industries,

aquatic eco-tourism and other tourism reliant on fishing;

(d) to foster the development of commercial and recreational fishing and

aquaculture including the establishment and management of aquaculture

facilities for community or commercial purposes;

(e) to achieve the optimum economic, social and other benefits from the use of fish

resources;

(f) to enable the allocation of fish resources between users of those resources;

(g) to provide for the control of foreign interests in fishing, aquaculture and

associated industries;

(h) to enable the management of fish habitat protection areas and the Abrolhos

Islands reserve.

2.2 Description of current management regime The Fish Traps Prohibition Notice 1994 prohibits the use of fish traps in all WA

waters. Fishers in the NDBSCF operate under the authority of an Exemption issued

under Section 7 of the FRMA. These Exemptions have a number of conditions

attached to them that act as the management arrangements for this fishery. The

management arrangements are predominately input based and include:


• Species restrictions. (The fishery targets blue swimmer crab. Coral crab and sand

crab may also be taken as by-product. However, as a condition of the Exemption

held by the operator, all other bycatch must be immediately returned to the water);

• A highly precautionary minimum size limit of 135mm CW has been set. (This

measure protects brood stocks and, in addition, facilitates equitable resource

sharing with recreational fishing, where there is a minimum size limit of 127mm

CW);

• All berried females must be returned to the water within 5 minutes of the crab trap

being pulled.

• The return of berried females and undersize crabs minimises the potential for

recruitment overfishing as the minimum size is well above the estimated size at

sexual maturity (< 100mm CW);

• The number of Exemptions granting commercial access to this fishery is presently

limited to two (these were granted through the DFWA Developing New Fisheries

Policy. The NDBSCF is currently closed to new exemptions and the policy is to be

reviewed and revised before the NDBSCF is reopened. It is extremely unlikely

that more crab operators would be approved for the same areas and new applicants

would be required to demonstrate sustainable practices. While there are no current

plans for more exemptions, this does not prevent applications when the

Developing New Fisheries Policy is reopened);

• The Exemptions authorise a total of 600 commercial traps and two licensed boats

to operate in the fishery;

• Trap design must be approved by DFWA. (Traps are purpose designed to enable

the escape of non target species and juvenile and undersized crabs - to

approximately 120mm); and

• Strict spatial restrictions designate the commercial fishing zone (Fig 6).

(A complete list of Exemption conditions is attached as Appendix A, detailed

maps of commercial fishing zone, including the restricted areas, are listed under

Appendix B, Figs 10-16).


Figure 6. The NDBSCF. (Multiple lines indicate slightly differing fishing boundaries

for each Exemption holder. Exemption holder one is permitted to fish within the 115°6’60 E to 120° E, Exemption holder two is permitted to fish within the zones 115° E to 116°45’ E and 117° E to 120° E. The NDBSCF contains exclusion zones where commercial fishing is prohibited (Appendix B, Figs 6-11 for details). In addition, the Exemption holders may not fish within 400 metres of any tidal creek or river mouth between 115o06.5’ east longitude and 120o east longitude (Appendix A).

2.3 Availability of documented management arrangements Exemptions issued under the FRMA are publicly available documents. Information

and copies of the exemptions can be obtained from The Register, DFWA on 08 9482

7369. The Fish Resources Management Act 1994 and subsidiary legislation can be

viewed at <www.slp.wa.gov.au>.

2.4 Consultative process for developing management regime The NDBSCF was established under the DFWA’s Developing New Fisheries policy

which involves consultation with a variety of stakeholders including WA Fishing

Industry Council, Recfishwest, RRFAC, local environmental bodies, local council,

local indigenous bodies and other interest groups.


The DFWA also undertakes consultation with community stakeholders,

representatives of the recreational sector, the WA Fishing Industry Council and other

interested parties prior to amending or introducing new policy/legislation. While no

formal consultative arrangements are currently in place for the NDBSCF, the

management process continues to occur in line with DFWA’s Developing New

Fisheries policy. In the case of the NDBSCF, there has been consultation within

DFWA, and with CALM, Conservation Council of WA and the NDBSCF operators.

DFWA also sought feedback from Recfishwest, the West Australian Fishing Industry

Council and the WA Department of Environment.

2.5 Expertise and community involvement in management of the fishery Management of the NDBSCF is the responsibility of the DFWA. DFWA Research

Division provides technical and research expertise, Commercial Program oversees the

strategic management and policy aspects whilst the Regional Services Branch delivers

enforcement of the specified management arrangements.

The RRFAC provides the government with advice on regional recreational fishing

issues. Feedback on management components relating to the NDBSCF has been

sought from the local RRFAC (Karratha), particularly in relation to any proposed

management changes.

2.6 Objectives of the management regime The DFWA has adopted a risk adverse approach and applied a precautionary principle

to the ongoing management of the NDBSCF while it recognises the potential

contribution of the fishery developers it does not guarantee future access to initial

participants of the fishery. The objective of the management regime is sustainable

development of the fishery. Broad strategies of the management regime are listed

below.

Maintaining fish biomass and recruitment by

• Limiting the number of participants in the fishery (currently two exemptions).


• Restricting fishing methods and gear to be used in blue swimmer crab fishing

(trap design and number).

• Monitoring the catch of the blue swimmer crab fishery through statutory monthly

returns and logbook data.

Managing environmental interactions by

• Minimising the environmental impact of blue swimmer crab fishing methods by

specifying non-mechanical fishing methods.

• Minimising bycatch of non-target species by specifying trap design.

Reducing incidental fishing mortality by

• Minimising bycatch of non-target species by specifying trap design.

• Returning bycatch species to water within time limits.

Ensuring access to blue swimmer crab resources by non-commercial and non-

extractive users by

• Maintaining equitable access to blue swimmer crab stocks for recreational users

and minimising adverse interaction between commercial fishers and other users of

the marine environment, including non-extractive users through spatial controls

on commercial operators and size limit separation between commercial and

recreational users.

Enforcement and monitoring by:

• Maintaining an enforcement presence to prevent any breach of Exemption by the

licence holder.

• Monitoring the capture of blue swimmer crabs annually to restrict or adjust

management controls where necessary.

Providing Socio-economic return to the community by

• Providing employment and business opportunities.


2.7 Controls As previously stated, management of the NDBSCF is controlled by way of Exemption

(Appendix A). Exemption holders are required to abide by the conditions placed on

the Exemptions, which in the case of the NDBSCF include trap number and design,

spatial and biological restrictions.

Exemptions are typically granted for a period of one to five years, depending on

circumstances. They are specific to an authorised person/company and as such are

non transferable between operators. Limiting the number of Exemption holders is of

particular strategic importance and is intended to avert any possibility of overfishing

or habitat degradation.

Each Exemption has a specified expiry date following which the management

arrangements are reviewed. Expired Exemptions are not automatically re-granted,

instead a new application must be submitted and assessed according to current policy

requirements such as sustainability of fishing methods.

The review process for altering a current Exemption consists of either fishermen or

interest groups approaching DFWA or DFWA contacting the fishermen to review

arrangements. This process is well understood by stakeholders and the system is

sufficiently flexible such that the management process can respond to external stimuli.

2.8 Enforcement of management arrangements The activities of Exemption holders in the NDBSCF need to be consistent with the

management framework and legislation such that the expected outcomes and

objectives of the fishery will be achieved. Enforcement activity is currently

undertaken by DFWA Fisheries and Marine Officers stationed at Karratha. Exemption

holders must adhere to the specified management arrangements; non-compliance may

result in prosecution and cancellation of the Exemption.

The NDBSCF is not currently managed as a discrete compliance project. This means

time and budget available to deliver compliance monitoring, enforcement and

community awareness activities to the fishery are included in the "Commercial Other

Fishery Compliance North".


The Karratha District Office currently services the fishery by delivering a range of at-

sea and on-land inspections, with the majority of checks being carried out on-land at

point of landing (in port) and processing inspections (at the processing establishment).

The processing establishment based inspections have occurred at Point Samson.

These inspections have focussed on the operator's compliance with minimum legal

size and totally protected fish requirements (berried crabs), checking that no bycatch is

being retained and/or consigned, that the vessels and fishers hold current DFWA

authorisations, that the operator and vessel have been nominated according to the

Exemption and that the gear being used complies with relevant requirements.

Finally, this fishery operates in very close proximity to the Karratha township and

generates a degree of community interest given that there has not previously been a

commercial crab fishery in the area. To manage the enquiries and concerns of the

community, the staff of the Karratha District Office have a range of community

awareness services, including providing advice to recreational fishers and the public,

relating to the permitted area of operation for the fishery, the rules governing its

operation and the status of the fishery.

To date a number of incidents of non-compliance have been detected including

offences relating to fishing outside the permitted area of operation (prosecuted and

convicted) and failure to hold a commercial fishing licence (dealt with by

infringement notices). Compliance monitoring, enforcement and community

awareness activities for this fishery will continue to be provided by the Karratha

District and Regional Offices.

2.9 Review and Performance Reporting It is important that the outcomes of the fisheries management processes administered

by the DFWA for the NDBSCF are available for review by external parties. It is also

important that the community is sufficiently informed on the status of the Fishery,

given that it is utilising a community resource. However, due to the small number of

commercial fishers operating from the region (fewer than five), catch information for

the NDBSCF has previously been prohibited from publication under the


confidentiality provisions of section 250 of the FRMA. Given the requirement for

specific catch information to be included in the ecologically sustainable development

(ESD) assessment, written permission has been granted from the operating exemption

holders to make these data publicly available.

Henceforth, review and reporting arrangements for this fishery will consist of:

• Annual Reports: There is an annual review of the performance for the major

aspects of the fisheries through the completion of the “State of the Fisheries”

report. A summary of this application and updated annual catch data will be

presented within the DFWA’s Annual Report and/ or the State of the Fisheries;

and

• ESD: Following completion of this application the DFWA will publish it as part

of the ESD Report Series which will be available from the DFWA’s website.

Further indicators and performance measures, based on fisheries dependent data, will

be determined through the management planning process and in conjunction with any

ongoing development of the fishery.

2.10 Assessment of any adverse impacts of the fishery on marine ecosystem Blue swimmer crabs are an important member of shallow benthic ecosystems. They

are opportunistic, bottom-feeding carnivores and scavengers and are most active in

foraging and feeding at sunset (Smith and Sumpton, 1987). Their diet primarily

consists of a variety of sessile and slow moving invertebrates, including bivalve

molluscs, crustaceans, polychaete worms and brittle stars (Edgar, 1990).

The smooth stingray, southern fiddler and gummy shark are known predators of adult

crabs in South Australia. Predators of blue swimmer crabs in WA have not been

widely identified, however crabs are a known food source for loggerhead turtles

(Caretta caretta) (Dr R Prince 2005, CALM, Perth office, pers. comm., 12 August).

This turtle species is primarily carnivorous and, in addition to various crabs, also feeds

on other shellfish, sea urchins, jellyfish, benthic gastropods and bivalve molluscs

(DEH 2005, last revised 29 August 2005, viewed 6 September 2005

<www.deh.gov.au/coasts/species/turtles/loggerheads.html>; Australasian Regional

Association of Zoological Parks and Aquaria 2005, viewed 22 August 2005


<www.arazpa.org.au/Education_FactSheets_Loggerhead.htm>; Marine Bio 2005,

viewed 6 September 2005 < www.marinebio.org/species.asp?id=163>).

A significant population of loggerhead turtles, including breeding females, resides

near Shark Bay (another blue swimmer crab fishery approximately 500 km south of

Onslow). When not breeding these turtles range out to sea and along the coast. The

abundance and distribution of this particular population is only partially understood.

Loggerhead turtles are reported in Nickol Bay (central to the NDBSCF) on a very low

frequency (F Stanley 2005, CALM, Karratha office, pers. comm., 25 August).

Due to its size, developmental status and fishing method employed, significant adverse

impacts of this fishery on the marine ecosystem are considered unlikely. For further

detail on potential ecosystem impacts see Section 4.5.

3 METHOLOLOGY

3.1 Overview

This application is based upon the National ESD Reporting Framework. A major

reference for this assessment was the DEH approved Shark Bay Experimental Crab

Fishery (SBECF) ESD. There were several steps involved in completing the ESD

assessment for the NDBSCF. These were review of the SBECF ESD, consultation,

risk issue identification, reporting and appraisal.

3.2 Workshop The requirement for a formal ESD workshop was considered. Considerations that

were factored in included the output of a previous ESD workshop for the Shark Bay

Experimental Crab Fishery (SBECF), similarities between SBECF and the

NDBSCF and the number of on hand fisheries experts available for informal

consultation. It was determined that a formal risk assessment workshop for the

NDBSCF was unnecessary. This decision was reached through consultation with

DFWA experts from the Fish Habitat Protection Program, the Recreational Fishing

Program and the Commercial Fishing Program. The basis for the decision was the

extensive documentation developed during the SBECF ESD risk assessment

workshop, much of which was deemed applicable to NDBSCF. Similarities

between the two fisheries include that they:

• Target the same species;

• Permit the same byproduct species;

• Are associated with similar non-retained species;

• Occur in warm sub tropical (SBECF) and tropical (NDBSCF) waters;

• Employ identical fishing methods; and

• Have limited protected species interaction.

In addition, the NDBSCF is the smaller of the two fisheries with figures from 2003

and 2004 indicating that the NDBSF accounted for less than 8% and 6%

respectively, of the state-wide blue swimmer crab catch (SBECF accounted for

greater than 50%). Also factored in was a general objection from external

stakeholders towards repeatedly participating in the ESD process, especially for

what is considered a minor fishery in comparison to others.


Instead, consultation with Exemption holders, and internal and external

stakeholders occurred via independent liaison and feedback. This took place

throughout the ERA framework, documentation, report drafting and review periods.

3.3 Risk and issue identification and categorisation The risk issues that needed to be addressed for this fishery were determined through

an internal consultation process. Due to the similarities between the NDBSCF and

the SBECF, risk issues raised and information generated during the ESD

application for SBECF were used as a starting point for the development of the

application for the NDBSCF. These were reviewed and removed or adapted as

deemed appropriate through consultation with experts. The agreed issues are

diagrammatically represented in component trees in the relevant sections (Figs 7-9).

An Ecological Risk Assessment (ERA) process was adopted to evaluate the risk

associated with each issue. Through this process the ‘likelihood’ and ‘consequence’

of each identified risk actually occurring was assessed and a final Risk rating for

each issue was determined (Table 1).

Table 1. ERA Risk table

Consequence (C)

Likelihood (L) Negligible Minor Moderate Severe Major Catastrophic Remote Rare Unlikely Possible Occasional Likely

For each identified risk issue, reporting and a management response appropriate to

the Risk rating were detailed (Table 2).


Table 2. ERA Risk ratings and required response. RISK Rating

Rank Likely Management Response Reporting

Negligible (N)

0 Nil. Short justification.

Low (L)

1 None specific. Full justification.

Moderate (M)

2 Specific management needed. Full performance report.

High (H)

3 Possible increases to management

activities needed. Full performance report.

Extreme (E)

4 Likely additional management activities needed.

Full performance report.

Justifications for assigning low priority or low risk were also recorded.


4. ESD ASSESSMENT

PRINCIPAL 1

A fishery must be conducted in a manner that does not lead to over-

fishing, or for those stocks that are over-fished, the fishery must be

conducted such that there is a high degree of probability the stock(s) will

recover.

4.1 Objective 1 The fishery shall be conducted at catch levels that maintain ecologically

viable stock levels at an agreed point or range, with acceptable levels of

probability.

Blue swimmer crabs

Primary Species

Coral crabs Sand crabs

By-Product Species

Retained Species

Figure 7. Retained species in the NDBSCF.

This fishery is managed conservatively by way of Exemption and input

controls. Biology and distribution of the catch species have been factored into

management planning and decisions. The risk of the fishery to blue swimmer

crab (P. pelagicus) stocks is moderate and the risk to the two potential by-

product species coral crabs (C. cruciata) and sand crabs (O. australiensis) is

negligible. All three species are early maturing, have high fecundity and short

lifecycles, such biological traits are associated with a relative resistance to

overfishing (Adams 1980). An informal survey conducted by DFWA Research

Division in 2002 found low levels of coral crab bycatch; coral crabs have been

reported at low catch levels through the log book system confirming this. No

sand crabs have been recorded as by-product.


Information requirements

4.1.1 There is a reliable information collection system in place appropriate to the

scale of the fishery. The level of data collection should be based upon an

appropriate mix of fishery independent and dependent research and

monitoring.

Data are mostly collected through fishery dependent means. Some data have

also been obtained through the current and past fishery independent research

projects. The fishery dependent data collection systems (CAES) and purpose

designed logbooks are currently in place and are used to monitor the total

catch, effort and catch rates for the fishery. Supplying timely and correct

information for capture through these systems is a condition of Exemption and

is compulsory in order to maintain access to the NDBSC resource. The catch

data reported by fishers are considered reliable. The penalties for submitting

incomplete or inaccurate data are a significant deterrent to overfishing or under

declaring catch.

The DFWA recognises the need for more fishery independent data collection

systems. One project currently underway is examining the stock/recruitment

relationship of blue swimmer crabs (FRDC project 01/068) though this work is

not focused on NDBSCF but rather on the larger and longer established

Cockburn Sound crab fishery.

A summary of current data collection, research and monitoring activities is

tabled below.


Table 3. Research and monitoring activities for blue swimmer crab

Monitoring Activities

Information Collected Robustness

CAES returns Provided on a monthly basis. Includes catch and effort data.

Medium

Purpose designed logbooks

Catch and effort data. Specific details: • Licence number, vessel name and

date; • Any non-fishing periods; • Names of collectors and collection

methods used; • Names of species collected; • Number of traps, fishing location,

trap depth and soak time; • Number of baskets of crabs and

weight of retained catch; • Bycatch; and

General remarks ie., weather, gear failure.

Medium-High

FRDC Project (1998/121)

Basic biology of crabs along WA coast including catchability. Commercial catch monitoring. Completed in 2000/01.

High

FRDC Project (2001/068)

Development of stock allocation and assessment techniques in the state’s blue swimmer crab fisheries.

Medium

Climatic data

Rainfall data; Wind data; and Swell Height conditions.

High

Assessment

4.1.2 There is a robust assessment of the dynamics and status of the species/fishery

and periodic review of the process and the data collected. Assessment should

include a process to identify any reduction in biological diversity and/or

reproductive capacity. Review should take place at regular intervals but at

least every three years.

There is one target species, blue swimmer crabs (P. pelagicus), for this fishery.

This crab species displays rapid growth, is highly fecund, and has a relatively

short life cycle, reaching the current legal minimum size within 18 months.


The minimum commercial size limit of 135mm CW is well above size at

sexual maturity (<100mm CW) and so provides a very high precautionary level

of protection to the brood stock. Also, all berried females must be returned to

the water. The stock-recruitment relationship for the species is currently

unknown, however the life history traits of blue swimmer crabs in combination

with the precautionary and relatively low level of fishing suggest that

recruitment dynamics are unaffected.

Acceptable catch ranges are yet to be determined for this fishery. There is

currently insufficient time series data for the commercial fishery to allow catch

ranges to be set, and as a developmental fishery some increase in catch rates is

still expected. Sufficient information should be available within the next five

years for acceptable catch ranges to be developed. In the meanwhile, catch

data are reviewed on an annual basis.

4.1.3 The distribution and spatial structure of the stock(s) has been established and

factored into management responses.

The blue swimmer crab, P. pelagicus, is found in nearshore marine and

estuarine waters throughout the Indo-West Pacific (Kailola et al., 1993). The

species lives in a wide range of inshore and continental shelf areas, including

sandy, muddy, algal and seagrass habitats, from the intertidal zone to at least

50m depth (Williams, 1982; Edgar, 1990).

Within Australia, P. pelagicus has been recorded in all states except Tasmania

(Stephenson and Campbell, 1959). In WA, the blue swimmer crab is found

from Albany on the south coast, north along the whole coastline to the

Northern Territory. Genetic analysis has shown that blue swimmer crab

populations on the west coast comprise distinct northern (sub tropical /

tropical) and southern (temperate) groups (Chaplin, 2000), so management of

the NDBSCF has been based on the Shark Bay model.


4.1.4 There are reliable estimates of all removals, including commercial (landings

and discards), recreational and aboriginal from the fished stock. These

estimates have been factored into stock assessments and target species catch

levels.

Monitoring programs for the NDBSCF, as outlined below, cover the catch by

the commercial fishers and any illegal fishing activities, which are obtained on

a monthly and yearly basis, respectively.

Table 4. Monitoring programs for the NDBSCF

Sector Catch Data Collected Frequency Commercial Catch and effort data Monthly Recreational Surveys Occasional Indigenous N/A N/A Illegal Estimated from

compliance data Annually

A specific 12 month survey of the recreational take was conducted during

1999-2000 (Williamson et al., 2005). Based on this survey the recreational

catch component (20 t), is currently estimated to be equivalent to up to 50

percent of the NDBSCF commercial catch. This is consistent with the high

popularity of the area with recreational crab fishers. There have been no

subsequent surveys to date. However, the take of recreational fishers was

factored in the development of the commercial NDBSCF by only allowing the

commercial fishery to develop in areas where there was not likely to be

conflict and limiting the number of crab traps used for commercial fishing

purposes.

There is no information on indigenous collection of blue swimmer crab in the

area, however the target crustaceans of the indigenous sector are generally mud

crab (Scylla spp) (B Fraser 2005, DFWA, senior management officer, pers.

comm. 10 August).


4.1.5 There is a sound estimate of the potential productivity of the fished stock/s and

the proportion that could be harvested.

Whilst the NDBSCF is a relatively new fishery, blue swimmer crabs have been

harvested in WA waters for more than a decade. The life history traits of the

blue swimmer crab, such as rapid growth, high fecundity and a relatively short

life cycle means the species is relatively robust to, and is able to recover

quickly from, overfishing (Adams, 1980; Melville-Smith et al., 2001). These

natural characteristics contribute to long-term security in recruitment to the

fishery.

In addition catch and effort data and general research have led to the

introduction of a conservative minimum size for blue swimmer crab as well as

management arrangements which ensure that recruitment overfishing does not

occur. For instance, the legal minimum size for the NDBSCF is 135mm CW,

which is well above the size at sexual maturity (<100mm CW) and as such is a

robust means of protecting the broodstock. Furthermore, WA research (FRDC

98/121) investigating the recruitment dynamics of blue swimmer crab stocks in

Cockburn Sound found that high levels of fishing had a minimal effect on the

fecundity of mature crabs. The researchers proposed that a reduction in legal

minimum size would still protect brood stocks and was therefore plausible

(Melville-Smith et al., 2001). No changes to the minimum legal size were

implemented.

Other research has suggested that WA blue swimmer crab stocks are comprised

of two genetically distinct groups. The two groups are differentiated by

latitude into northern torpical and southern temperate stocks. This research

also indicates that gene flow occurs for up to 300km and thereby links

localised crab populations.


Management responses

4.1.6 There are reference points (target and/or limit) that trigger management

actions including a biological bottom line and/or a catch or effort upper limit

beyond which the stock should not be taken.

As stated above, crab stocks in the NDBSCF are monitored using the annual

catch, effort and catch per unit effort values. Acceptable catch ranges are yet to

be determined as there is currently insufficient time series data for the

commercial fishery to allow ranges to be set, and as a developmental fishery

some increase in catch rates is still expected. Sufficient information should be

available within the next five years for acceptable catch ranges to be

developed.

As the fishery is still in the exploratory phase, catch rate is expected to

fluctuate, showing a general increase as the fishers’ knowledge of local stocks

improves. In the meanwhile, catch data are reviewed on an annual basis and

any significant increase or decrease in catch or catch rate, outside previous

catch levels in the fishery, will trigger FDWA to look more closely at

exploitation rates when the data are reviewed. If the change cannot explained

by environmental variations or industry dynamics and behaviour, then

strategies which offer further protection to the breeding stock will be

considered. The options in this regard include either a reduction in trap

numbers and/or the introduction of seasonal closures. These can be

implemented within a season or prior to the beginning of the next season.

4.1.7 There are management strategies in place capable of controlling the level of

take.

Management strategies controlling the fishery include a limit on the number of

commercial fishing operators (two authorised by Exemption), the type of

fishing gear employed and defined zones areas where commercial crab

trapping can take place (Appendix A). The management provisions are

considered robust and enforceable and enable immediate reductions in fishing

effort if necessary.


4.1.8 Fishing is conducted in a manner that does not threaten stocks of by-product

species.

The NDBSCF is managed under the FRMA by way of Exemption. Whilst the

fishery is focussed on the blue swimmer crab, coral crab and sand crab may

also be taken as by-product. To date there have been no recorded catches of

sand crabs in the NDBSCF and only small quantities of coral crabs. Due to

their broad distribution, short life cycle and high fecundity, specific and

ongoing monitoring of by-product (other than the monthly returns submitted by

fishers) is deemed unnecessary.

As a condition of the Exemptions all bycatch other than sand and coral crabs

must be immediately returned to the water. This condition ensures high level

of survival.

4.1.9 The management response, considering uncertainties in the assessment and

precautionary management actions, has a high chance of achieving the

objective.

The NDBSCF is currently managed through input controls (Appendix A), and

take is monitored monthly and assessed annually.

The ability to develop or alter management strategies to further protect

spawning stock is provided for within the FRMA and the Fish Resources

Management Regulations 1995 (the FRMR). Strategies could be implemented

either within a season or prior to the next year.


4.2 Objective 2 Where the fished stock(s) are below a defined reference point, the fishery

will be managed to promote recovery to ecologically viable stock levels

within nominated timeframes.

Spawning stock is currently protected through management provisions. As

detailed in Section 4.1.6, there are several strategies available to the DFWA

which offer further protection to the spawning stock, including a reduction in

trap numbers, introduction of a seasonal closure or complete closure of the

fishery. Such actions could be implemented at short notice.

PRINCIPLE 2

Fishing operations should be managed to minimise their impact on the

structure, productivity, function and biological diversity of the ecosystem.

4.3 Objective 1. The fishery is conducted in a manner that does not threaten bycatch

species.

Protected Sp

Other crabs

Finfish

Octopus

Starfish

Other

Capture

Dolphins

Dugongs

Sea Birds

Turtles

Whales

Direct interactionbut no capture

Non RetainedSpecies

Figure 8. Non retained species associated with the NDBSCF.


A number of species were identified in this fishery (Fig 8). While it can be

expected that there will be occasional interactions between these species and

the fishermen, the very low number of fishermen, the small scale of their

operations and relatively passive trap nature of their fishing operations

suggests that any injuries, mortalities or similar adverse impacts will be

extremely rare and none have so far been recorded. As such all of the

identified species were ranked as having a negligible risk from the NDBSCF

(Table 5).


4.3.1 Reliable information, appropriate to the scale of the fishery, is collected on the

composition and abundance of bycatch.

Information on the composition and abundance of bycatch has been obtained

through liaison with the fishers and compliance monitoring in the NDBSCF

and in other WA fisheries using similar fishing methods (i.e. SBECF). DFWA

has performed at-sea monitoring of catch and bycatch in the NDBSCF whilst

undertaking compliance and targeted research activities.

Assessment

4.3.2 There is a risk analysis of the bycatch with respect to its vulnerability to

fishing.

Bycatch associated with the NDBSCF consists of retained and non-retained

species. A risk assessment for the identified non-retained/bycatch species has

been completed (Appendix C). In this assessment species directly interacting

with the fishery but not captured during fishing were also considered. The risk

of the fishery to each of the catch categories ie., retained, non-retained and

interacting species was rated negligible, a summary of the assessment is tabled

below (Table 5).


Table 5. Summary of risk assessment outcomes for bycatch/retained and non-retained species related to the NDBSCF. SPECIES RISK SUMMARY JUSTIFICATION Retained Species Blue swimmer crab – Portunus pelagicus

N Target species.

Coral crab – Charybdis cruciata

N Permitted. Low recorded catch.

Sand crab – Ovalipes australiensis

N Permitted. No recorded catch.

Non Retained Species

Crabs – various spp

N Caught in low number. Must be returned to water.

Fin Fish (various spp) including: Box Fish – family Ostraciidae Butterfish – Pentapods spp Leather Jackets – family Monacanthidae NW Blowfish – Lagocephalus spp

Emperor – Lethrinus spp

N Traps minimise capture (section 1.5). Infrequently caught in low numbers. Must be returned to water.

Octopus – various spp

N Traps minimise capture. Frequently caught in shallow waters due to abundance. Must be returned to water.

Starfish – various spp

N Occasionally attach to trap. Insignificant catch level. Must be returned to water.

Invertebrates – Marine gastropods

N Occasionally attach to trap. Insignificant catch level. Must be returned to water.


TABLE 5. Continued.

SPECIES RISK SUMMARY JUSTIFICATION Interaction but not captured (Protected spp) Dolphins Bottlenose – Tursiops truncates Common – Delphinus delphis

N No reports of dolphins becoming entangled within the fishing gear of the NDBSCF. (D Coughran 2005, CALM pers. comm., 30 August). Neither CALM nor DFWA are aware of any problems directly associated with the fishery.

Dugongs – Dugong dugon

N Protected under Special Protected Fauna under WA Wildlife Conservation Act 1950. No reports of dugongs becoming entangled within the fishing gear of the NDBSCF. (D Coughran 2005, CALM pers. comm., 30 August). Although there is the potential and while some animals present with scars, there is no particular issue with boats running over dugongs and there are no reports or known cases of dugongs being injured or run over by boats from the NDBSCF fishery (D Coughran 2005, CALM pers. comm., 7 September). Neither CALM nor DFWA are aware of any problems directly associated with the fishery.

Manta Rays – Manta biostris

N There is the potential that these animals could entangle. Manta rays are unable to swim backwards hence there is a possibility that they could swim into crab trap rope which then wraps around their horns. There has never been a reporting of entanglement of manta rays in the location of the NDBSC and there is no known problem (D Coughran 2005, CALM pers. comm., 07 September).

Seabirds various

N All seabirds are protected species. A number of seabirds are associated with crab fishing. Birds are usually seen following, circling or settling near boats seeking discarded provisions or catch. Pied cormorants (Phalacrocorax varius) have been identified taking catch from soaking traps in other fisheries. On odd occasions these birds have also been found drowned after getting their necks stuck in the exit holes of the traps. This problem has not been reported in the NDBCSF. Numbers of pied cormorant and fishing traps are both relatively few in the area and the issue is unlikely to have a greater than negligible impact (Dr N Dunlop. 2005, Conservation Council of WA, pers. comm., 09 September)


TABLE 5. Continued.

SPECIES RISK SUMMARY JUSTIFICATION Interaction but not captured (Protected spp) Turtles Flatback – Natator depressus Green – Chelonia mydas Hawkesbill – Eretmochylys imbricata Leatherback – Dermochelys coriacea Loggerhead – Caretta caretta

N

Protected under Special Protected Fauna under WA Wildlife Conservation Act 1950. Classified vulnerable under EPBC Act. Loggerhead classified as endangered under EPBC Act. A significant breeding population of Loggerhead turtles is known to reside in Shark Bay. (Crabs are one of many known food sources.) Unusual for this species to be seen in the area of NDBSCF (F Stanley 2005, CALM pers. comm., 25 August). Interaction with boats and equipment is considered unlikely. However, in the circumstance that interaction does occur the main risk is entanglement in ropes and lines rather than caught in traps. Less than one entanglement per year is recorded Statewide. No reports of whales becoming entangled within the fishing gear of the NDBSCF (D Coughran 2005, CALM pers. comm., 30 August). Neither CALM nor DFWA are aware of any problems directly associated with the fishery. All forms of turtle mortality need to be minimised.

Whales Hump back – Magaptera novaengliae Southern Right Whale –Eubalaena australis

N Protected under Special Protected Fauna under WA Wildlife Conservation Act 1950. Regularly observed migrating along coastline. Interactions recorded in fisher logbook. Fishers are required to report all interactions to DFWA and CALM. No reports of whales becoming entangled within the fishing gear of the NDBSCF (D Coughran 2005, CALM pers. comm., 30 August). Neither CALM nor DFWA are aware of any problems directly associated with the fishery.


4.3.3 Measures are in place to avoid capture and mortality of bycatch species unless

it is determined that the level of catch is sustainable (except in relation to

endangered, threatened or protected species). Steps must be taken to develop

suitable technology if none is available.

Not Applicable.

4.3.4 An indicator group of bycatch species is monitored.

4.3.5 There are decision rules that trigger additional management measures when

there are significant perturbations in the indicator species numbers.



objective.

The risks associated with bycatch species will be reassessed at the first major

review of this fishery. This will occur within five years, as a requirement of

the DFWA ESD policy.

There are no figures for the proportion of total catch that bycatch on average

comprises. Due to the method of fishing the proportion of bycatch is extremely

low. This has been verified at sea by DFWA researchers and compliance staff.

Most recently (September 2005) a DFWA Fisheries and Marine Officer

accompanied one of the operators in the NDBSCF for a day while the fisher

undertook routine activities. Two hundred seventy crab traps were retrieved.

Bycatch consisted of:

• nine fish – all were small and juvenile (under 10cm approximately).

Species included leatherjacket, puffer fish and cod;

• Marine gastropods;

• several hermit crabs;

• 15 starfish.


All bycatch specimens were in a healthy state. They were discarded

immediately and nothing was translocated. The bycatch on this occasion was

estimated at less than 0.7% of the landed crab catch.

Given the relatively low interactions of the fishery with non-retained species

and the highly selective method of fishing (i.e. purpose designed traps) used in

the fishery it is likely that the level of interaction will continue to be only

minimal with only acceptable levels of impact occurring.

4.4 Objective 2. The fishery is conducted in a manner that avoids mortality of, or injuries

to, endangered, threatened or protected species and avoids or minimises

impacts on threatened ecological communities.


4.4.1 Reliable information is collected on the interaction with endangered,

threatened or protected species and threatened ecological species.

The information provided in this submission regarding the interaction of this

fishery with endangered, threatened and/or protected species is from fishers

within this fishery and unpublished data from CALM (D Coughran; Dr R

Prince; F Stanley, 2005, CALM, pers. comm.).

Assessment

4.4.2 There is an assessment of the impact of the fishery on endangered, threatened

or protected species.

A risk assessment for each of the identified non-retained/bycatch

species/groups (including those with direct interaction but no capture) was

completed for the SBECF. This assessment was informally reviewed for the

purposes of evaluating the impact of the NDBSCF on endangered, threatened

or protected species. Input from experts was sought. The assessment

concluded that the NDBSCF did not capture any endangered, threatened or

protected species (Table 5.).


For the direct interaction but no capture category the assessment concluded that

the fishery was of negligible risk to endangered, threatened or protected species

including whales and dolphins and turtles (Table 5).

4.4.3 There is an assessment of the impact of the fishery on threatened ecological

communities.

There are no threatened ecological communities associated with this fishery.

Management

4.4.4 There are measures in place to avoid capture and/or mortality of endangered,

threatened or protected species.

Currently there are no measures in place because to date there have been no

reported captures, entanglements or interactions between the fishery and any

protected species (endangered, threatened or vulnerable). However, fishers are

required to report all interactions to DFWA and CALM. Should any

interactions occur, management arrangements would be reviewed and

measures implemented as required.

4.4.5 There are measures in place to avoid impact on threatened ecological

communities.

Not applicable.



objective.

There have been no reported interactions (including captures) of protected

species with this fishery; therefore it is unlikely that this fishery is having any


unacceptable impacts on these species. As specified in Section 4.4.4 the

management provisions for the NDBSCF require fishers to record interactions

in logbooks and report all interactions to DFWA and CALM.

4.5 Objective 3.

The fishery is conducted, in a manner that minimises the impact of fishing

operations on the ecosystem generally.

Bait Collection(not specifically by this fishery)

Ghost Fishing

Sand Seagrass

Benthic Biota

FishingTrophic levels

Removal of/damageto organisms

Bait

Stock enhancement(not for this fishery)

Translocation

Discarding/Provisioning

Addition/movementof biological material

Impacts on biologicalCommunity

Fuel Usage/Exhaust

Greenhouse GasEmissions

Air Quality

Debris

Oil discharge

Water Quality

Substrate Quality

Other

General Environment

Figure 9. General environment issues related to NDBSCF.

Six general ecosystem and environment issues have been identified in

association with the fishery (Fig 9) all of which were given a negligible risk

rating (Table 6).



4.5.1 Information appropriate for the analysis in 4.5.2 is collated and/or collected

covering the fisheries impact on the ecosystem and environment generally.

Appropriate levels of information (in regards to the scale of the fishery) were

obtained for most of the issues identified and the level of risk was sensibly

determined. Input was sought from the DFWA, CALM, Conservation Council

of WA and the NDBSCF operators. DFWA also sought feedback from

Recfishwest, the West Australian Fishing Industry Council and the WA

Department of Environment.

The collated information includes data collected directly relating to the fishery

– in terms of catch and effort and field observations made by DFWA staff. In

addition, current and future research (as discussed in Section 2.2.4) relating to

this fishery and other similar fisheries (ie. fisheries using purpose designed

traps) has and will continue to provide the DFWA with relevant information to

allow for the development of appropriate management responses.

Assessment

4.5.2 Information is collected and a risk analysis, appropriate to the scale of the

fishery and its potential impacts, is conducted into the susceptibility of each of

the following ecosystem components to the fishery.

An informal, internal risk assessment was completed on each of the identified

issues relevant to the fishery (Appendix C). The identified issues, risk rating

outcomes, and justifications comprising the assessment are summarised in

Table 6. All of the identified potential ecosystem issues were rated to be of a

negligible risk level.


Table 6. Summary of risk assessment outcomes for environmental issues related to the NDBSCF (see Appendix C for full details).

ISSUE RISK SUMMARY JUSTIFICATION Impact from addition/movement of biological material:

Discarding/Provisioning N Traps are usually left soaking for 24 hours between hauls and therefore little bait is left when the pots are brought to the surface. The amount of bait provisioned to non target species is considered minor and of negligible impact, this is particularly due to the small scale nature of the NDBSCF which occurs over a large area.

Impact from removal of/damage to organisms:

Ghost fishing N The gear used in this fishery generates minimal non-retained species and the purpose design of the traps (mesh sizes of 2 inch and 4 inch) is such that they do not ‘ghost fish’ if lost. Anecdotal evidence and observations by Fisheries staff clearly show that blue swimmer crabs (and other large animals) are rarely seen in any type of trap without bait. This indicates that animals are able to escape from the trap if given enough time.

Impact to benthic biota – Sand

N Sand and associated biota are not brought to the surface in commercial blue swimmer crab traps. The mesh used on traps is large enough to allow the escape of any sand dwelling macrobenthos. However, some macrobenthos may be directly impacted when traps are placed on the benthos. Fishing with traps results in limited habitat disturbance, with only minor dragging of traps on the bottom during retrieval.

Impact to benthic biota – Seagrass

N In SBECF, seagrasses are occasionally directly impacted when brought to the surface with traps. This is a minor problem in SBECF, where there are extensive beds of large seagrasses. In NDBSCF seagrasses are of genera with a small size, and the problem is lesser.


Table 6. Continued.

ISSUE RISK SUMMARY JUSTIFICATION Impact from addition/movement of biological material:

Impacts of fishing Trophic Level

N The commercial take of crabs occurs in a very small geographic area compared to the distribution of the species along the north coast of WA. It thus represents a relatively small portion of the biomass of crabs in these areas, which is effectively renewed annually. Secondary food chain effects are likely to be minimal in these fisheries. There are no animals known to feed exclusively on blue swimmer crabs.

Other Impacts – Water Quality

Debris N There is a general code of practice among crab fishers to return packaging and garbage back to the shore. Waste disposal bins are located at all points where commercial boats tie up. Fishers are aware of the related public perceptions and sensitivities. There is a small potential for lost lines of traps, discarded bait boxes and nylon bands and other debris to impact on water quality.

Management responses

4.5.3 Management actions are in place to ensure significant damage to ecosystems

does not arise from the impacts described in 4.5.1

The most important management methods required to ensure minimal impact

on the broader ecosystem include maintaining significant stock/biomass levels

of the target species.

In most cases this serves to achieve both of the objectives of firstly, having a

sustainable fishery and secondly, minimising the potential for any trophic

interactions. Other management measures such as limited entry, minimum


sizes, biological restrictions, and gear restrictions further minimise the

potential for ecosystem impacts.

4.5.4 There are decision rules that trigger further management responses when

monitoring detects impacts on selected ecosystem indicators beyond a

predetermined level, or where action is indicated by application of the

precautionary approach.

No ‘non-retained species’ or ‘general environment’ issues identified received a

risk rating greater than ‘negligible’. Hence none of the issues were deemed to

be of sufficient risk to require specific target levels to be set. As discussed in

4.5.2 above, the most important management methods required to ensure that

there is minimal impact on the broader ecosystem include maintaining

significant stock/biomass levels of the target species.

As previously stated (Section 4.1.6) the fishery is still in the developmental

phase. Catch data are reviewed on an annual basis and any significant increase

or decrease in catch or catch rate beyond previous levels will trigger DFWA to

look more closely at exploitation rates. If major changes in annual landings or

CPUE were to be recorded within a season, then investigations would be

undertaken to identify the cause of these changes. DFWA can take action, if

required, within a season or prior to the next year depending on need.

Strategies that are available to DFWA, which would offer further protection to

the spawning stock, include a reduction in trap numbers, or introduction of a

seasonal closure.


4. REFERENCES Adams, P. B. 1980. Life history patterns and their consequences for fisheries management. Fishery Bulletin 78, (1): 1-12

Bryars, S. R. 1997. Larval dispersal of the blue swimmer crab Portunus pelagicus Linnaeus (Crustacea: Decapoda: Portunidae) in South Australia. Flinders University, Australia. Unpublished PhD thesis, 256 pp.

Campbell, G. R. and Fielder, D. R. 1986. Size at sexual maturity and occurrence of ovigerous females in three species of commercially exploited portunid crabs in south-east Queensland. Proceedings of the Royal Society of Queensland 97: 79-87.

Chaplin, J., 2000. ‘Genetic (microsatellite) determination of the stock structure of the blue swimmer crab in Australia’ FRDC project report 98/118.

Edgar, G.J., 1990. Predator-prey interactions in seagrass beds. The influence of macrofaunal abundance and size-structure on the diet and growth of the western rock lobster Panulirus cygnus George. Journal of Experimental Marine Biology and Ecology 139: 1-22.

Ingles, J. A., and Braum, E. 1989. Reproduction and larval ecology of the blue swimming crab Portunus pelagicus in Ragay Gulf, Philippines. Int. Revue. ges. Hydrobiol. 74: 471-490.

Jones, D. and Morgan, G. 2002. A field guide to crustaceans in Australian waters. Western Australian Museum. Perth. 224pp.

Kailola, P. J., Williams, M. J., Stewart, P. C., Reichelt, R. E., McNee, A. and Grieve, C. (1993). Australian Fisheries Resources. Bureau of Resource Sciences, Department of Primary Industries and Energy, and the Fisheries Research and Development Corporation, Canberra, Australia.

Meagher, T. D. 1971. Ecology of the crab Portunus pelagicus (Crustacea: Portunidae) in south-western Australia. University of Western Australia. Unpublished PhD thesis, 232 pp.

Melville-Smith, R., Bellchambers, L. M. and Kangas, M. 2001. The collection of fisheries data for the management of the blue swimmer crab fishery in central and lower coasts of Australia. FRDC Final Report 98/121.

Potter, I. C, Chrystal, P. J. and Loneragan, N. R. 1983. The biology of the blue manna crab Portunus pelagicus in an Australian estuary. Marine Biology 78: 75-85.

Potter, I. C, de Lestang, S. and Melville-Smith, R. 2001. The collection of biological data required for management of the blue swimmer crab fishery in the central and lower west coasts of Australia. FRDC Final Report 97/137.

Smith, H. 1982. Blue crabs in South Australia – their status, potential and biology. SAFIC, 6(5): 6-9.

Smith, G. S. and Sumpton, W. D. 1987. Sand crabs a valuable fishery in southeast Queensland. Queensland Fisherman, 5: 13-15.

Stephenson, W. and Campbell, B 1959. The Australian portunids (Crustacea: Portinudae). III. The genus Portunus. Australian Journal of Marine and Freshwater Research, 10: 84-124.

Van Engel, W. A. 1958. The blue crab and its fishery in Chesapeake Bay. Part I. Reproduction, early development, growth and migration. Commercial Fishing Review 20: 6-17.

Williams, M. J. 1982. Natural food and feeding in the commercial sand crab Portunus pelagicus Linnaeus, 1766 (Crustacea: Decapoda: Portunidae) in Morton Bay, Queensland. Journal of Experimental Marine Biology and Ecology, 59: 165-176.

Williamson, P. C., Sumner, N. R., Malseed, B. E. 2005. A 12-month survey of recreational fishing in the Pilbara region of Western Australia during 1999-2000. Fisheries Research Report. Department of Fisheries, Western Australia.


6. APPENDICES

Appendix A – Exemption Conditions of fishing in NDBSCF

Appendix B – Maps of the NDBSCF

Appendix C – ERA Ecological Risk Assessment


APPENDIX A - Conditions of fishing in NDBSCF

(Extract from a Section 7 Exemption instrument)

Schedule 1 Activities

To take blue swimmer, sand and coral crabs with a maximum of xxx crab traps of a design approved by the Research Division of the Department of Fisheries, within WA waters below the high water mark and to the 200 m isobath between 115o5’60 east longitude (Onslow) and 120o east longitude, except within the areas specified in Schedule 3.

Schedule 2 Conditions

1. This authorisation is non-transferable.

2. The activities specified in Schedule 1 may only be undertaken on the Licensed Fishing Boat LFB xxxx.

3. All berried female and undersize blue swimmer crabs, berried female and undersized coral crabs, mud crabs and all fish other than crabs taken by the crab traps referred to in Schedule 1, must be returned whole to the water and within 5 minutes of being landed aboard the authorised boat(s).

4. The details (name, address, CFL number) of any natural person operating the authorised boats on behalf of the Exemption holder must be provided to the Department of Fisheries Karratha District Office no less than one business day prior to that person fishing in the fishery on behalf of the Exemption holder.

5. No more than four persons shall fish from each authorised boat at any one time.

6. Crab traps referred to in Schedule 1 may not be pulled more than once in any 24 hour period (commencing at midnight).

7. Crab traps referred to in Schedule 1 must be either -

• attached to a rope with a surface float branded or stamped in legible characters with the LFB number of the relevant authorised boat, or

• attached to another crab trap used under the authority of this instrument, by a rope with a minimum length of 20 metres. A surface float branded or stamped in legible characters with the LFB number of the relevant authorised boat must be located at each end of the line of crab traps.

9. The exemption holder must-

• Ensure that all catch taken under the authority of this Exemption is included on Statutory Catch and Effort Returns submitted to the Department of Fisheries in accordance with Regulation 64 of the Fish Resources Management Regulations 1995.

• Record accurate and detailed daily crab catch data into provided research

logbooks, in the form prescribed by the Research Division. The research logbook must be returned to the Research Division by the 15th day of each month.


• Ensure that a written report is provided to the Executive Director by 15 January in

each year for which this Exemption is in effect in relation to fishing activities conducted under the Exemption during the period 1 January to 31 December of the previous year - including details of:

a) the quantity of crabs taken, the number of days spent fishing for crabs, the

type and quantity of gear used and the areas fished for crabs during each month of operation;

b) any bycatch of fish; c) the markets to which crabs was sold; d) progress towards achieving business plan objectives; and e) goals and targets for the following 12 months.

10. The payment of $1670.00 by way of donation to the Fisheries Research and

Development Fund, to be made by 1 March in each year for which this exemption is in effect.

11. The minimum legal size for blue swimmer crabs and coral crabs shall be 135 mm

by measuring from tip to tip of the posterior carapace spikes. 12. This Exemption will be subject to review if, in the opinion of the Executive

Director, the operation is likely to lead to conflict with any other relevant users of the marine environment, within the period for which it is in effect.

Schedule 3 1 The Exemption holder or any natural person fishing on his behalf, may not fish for blue

swimmer, sand crabs or coral crabs under authority of this exemption within 400 metres of any tidal creek or river mouth between 115o06.5’ east longitude (Onslow) and 120o east longitude.

2 The Exemption holder or any natural person fishing on his behalf, may not fish for

blue swimmer, sand crabs or coral crabs under authority of this exemption in the following areas:

a) within five (5) nautical miles of the base of the Beadon Groyne, Onslow, given as the intersection of longitude 115° 07.9’E and the high water mark on the mainland. b) Within the waters bounded by a line starting at the eastern extremity of Sloping point, then to the eastern extremity of Legendre Island, then along the high water mark of the north western shore of the island to it’s western extremity, then to the western extremity of Whittaker Island, then to the northeastern extremity of Enderby Island, then generally along the high water mark of the western shore to the western extremity, then to the eastern extremity of Eaglehawk Island, then along a line drawn through the southern most point of West Intercourse island to intersect the high water mark on the mainland, then along the high water mark to the commencement point. c) All waters bounded by a line commencing at the intersection of the high water mark on the north west coast of the mainland and 117° 13.20’ east longitude;


thence north along the meridian to the intersection of 20° 39.50’ south latitude (eastern side of Jarman Island); thence northerly along the geodesic to the intersection of 20° 37.60’ south latitude and 117° 13.00’ east longitude; thence north north west along the geodesic to the intersection of 20° 36.30’ south latitude and 117° 12.40’ east longitude; thence north west by west along the geodesic to the intersection of 20° 35.55’ south latitude and 117° 11.00’ east longitude (Cape Lambert); thence westerly along the geodesic to the intersection of 20° 35.60’ south latitude and 117° 10.35’ east longitude; thence west by south along the geodesic to the intersection of 20° 37.00’ south latitude and 117° 05.35’ east longitude (eastern end of Dixon Island); thence north by east along the geodesic to the intersection of 20° 34.90’ south latitude and 117° 05.90’ east longitude; thence west south west along the geodesic to the intersection of 20° 39.00’ south latitude and 116° 55.00’ east longitude; thence west by north along the geodesic to the intersection of the high water mark on the coastline and 20° 37.50’ south latitude; thence generally southerly, easterly, northerly and southerly along the high water mark to the commencement point.

d) within waters bounded by a line drawn from the intersection of longitude 118° 20.4”E and the mainland, then to the intersection of latitude 20° 15’S and longitude 118° 35’E, then to the intersection of longitude 118° 46’E and the mainland and then generally west along the high water mark to the commencement point.

Schedule 4 Period and Purpose

1. Period.

This instrument is valid from the date of signing until 11 July 2006.

2. Purpose. To -

(i) explore and/or develop the crab fishery and fishing technology of that activity under the provision of Section 7(3)(c) of the Fish Resources Management Act 1994. (ii) gather baseline data about inshore crab stocks between Onslow and 120o east longitude under a controlled management regime.


APPENDIX B – Maps of the NDBSCF (Figures 10-16)

EXEMPTION ONE (NDBSCF) External Boundaries


EXEMPTION TWO (NDBSCF) External Boundaries


EXEMPTION ONE and TWO (NDBSCF) Restricted Area – Schedule 3, 2a Commercial Fishing Not Permitted


EXEMPTION ONE and TWO (NDBSCF) Restricted Area – Schedule 3, 2b Commercial Fishing Not Permitted


EXEMPTION ONE (NDBSCF) Restricted Area – Schedule 3, 2c Commercial Fishing Not Permitted


EXEMPTION TWO (NDBSCF) Restricted Area – Schedule 3, 2c Commercial Fishing Not Permitted


EXEMPTION ONE and TWO (NDBSCF) Restricted area – Schedule 3, 2d Commercial Fishing Not Permitted


APPENDIX C – Ecological Risk Assessment (ERA) An assessment of the performance for each of the issues of sufficient risk to require specific management actions was completed using a standard set of report headings where operational objectives, indicators and performance measures, management responses etc were specified. An overview assessment of the fishery was completed including an action plan for activities that will need to be undertaken to enable acceptable levels of performance to continue or, where necessary, improve the performance of the fishery. This assessment was based upon the combined judgement of the participants at the workshop, who collectively had considerable expertise in the areas examined. RETAINED SPECIES

PRIMARY SPECIES

Blue Swimmer Crabs Rationale for Inclusion:

The blue swimmer crab is the major target species of the NDBSCF and therefore the potential impact of the fishery on their stocks needs to be assessed. ERA Risk Rating: Impact on breeding stock Likelihood: Remote, Consequence: Negligible Risk Rating: Negligible Blue swimmer crabs (Portunus pelagicus) inhabit coastal waters throughout WA. Commercially fished stocks are found in the area between Bunbury and Mandurah, the Peel/Harvey Estuary, Comet Bay (near Mandurah), Warnbro Sound, Cockburn Sound, the Swan/Canning Estuary, Shark Bay, Exmouth Gulf and Nickol Bay. Blue swimmer crabs are found in a wide range of inshore and continental shelf areas, from the intertidal zone to at least 50 m depth. This species has a rapid growth, is highly fecund, and has a relatively short life cycle, reaching the current legal minimum size within 18 months. The stock-recruit relationship for blue swimmer crabs is currently unknown, however their life history traits in combination with the relatively low level of fishing, indicates that the recruitment dynamics are unlikely to be affected. Under current management arrangements the potential for recruitment overfishing is minimised and the major risk would be for growth overfishing (ie the older age class). The minimum commercial size limit of 135mm CW, and recreational size limit of 127mm CW, is well above size at sexual maturity (<100mm CW) and so provides a very high precautionary level of protection to the brood stock. Also, all berried females must be returned to the water.


Operational Objective

To maintain, by way of an appropriate legal minimum size, the spawning stock of blue swimmer crabs at or above a level that minimises the risk of recruitment over fishing. Justification: Meeting this objective will ensure that there is sufficient breeding stock to continue recruitment at levels that will replenish what is taken by fishing, predation and other environmental factors. Indicator

Both annual catch levels and CPUE are used as indices of abundance for this fishery. Performance Measure

Acceptable catch ranges are yet to be determined for the NDBSCF as there is currently insufficient time series data for the commercial fishery to allow ranges to be set, and as a developmental fishery some increase in catch rates is still expected. Sufficient information should be available within the next 5 years for acceptable catch ranges to be developed. As the fishery is still in the developmental phase, catch data are reviewed on an annual basis and any significant, increase or decrease in catch or catch rate will trigger the DFWA to look more closely at exploitation rates. If major changes in annual landings or CPUE were to be recorded within a season, then investigations would be undertaken to identify the cause of these changes. Justification: The commercial minimum legal size for blue swimmer crabs of 135 mm CW in NDBSCF is well above the size at sexual maturity (100mm) and as such is expected to be a robust means of protecting the brood stock. Adequate protection of the breeding stock could still be achieved by lowering the legal minimum size (Melville-Smith et al., 2001). Berried females must be returned to the water and discarded undersize crabs are believed, from tag recapture data (Melville-Smith et al., 2001), to have a high rate of survival. In general, blue swimmer crabs are resilient to overfishing due to their short life span, rapid growth and high fecundity. Data Requirement for Indicator (and Availability)

Data Required Availability Commercial catch and effort data Catch and effort data are being collected by

both CAES and purpose designed logbooks. Stock /recruitment relationship Stock allocation and assessment techniques

being developed under the current FRDC grant (01/68).


Evaluation

Landings: The total commercial catch in the NDBSCF has increased from 9.9 t in 2001, the year of its establishment, to 64 t in 2003. In 2004 NDBSCF recorded a 24% decrease in catch, landing a total of 49.1 t. Fishing effort: Fishing effort is measured by the number of trap lifts. In 2001 dedicated trap fishermen in the NDBSC made 19200 trap lifts this increased to 68500 in 2003. In 2004, the NDBSCF recorded a 55% decrease in fishing effort, a total of 30660 trap lifts were made. Catch rate (CPUE): Trap catch rates in NDBSCF in 2004 were 1.8 kg/trap lift, up 360% from 0.5kg/trap lift in 2001 and up 180% from 1kg/trap lift in 2003. Robustness

Medium Whilst both catch and catch rate are used as indicators, CPUE is considered to be a more reliable index of abundance, than catch levels, as the NDBSCF is still in the developmental phase where increases in fishing effort can lead to increases in catch and CPUE. The catch data reported by fishers are considered reliable. Fisheries Management Response

Current: The NDBSF is managed under the FRMA by way of exemptions and conditions on FBLs, using input controls including:

• Species restrictions. The fishery is focussed on the blue swimmer crab. Coral and sand crabs may also be taken as by-product. However as a condition of the Exemptions held by the operators all other bycatch must be immediately returned to the water.

• A precautionary minimum size limit of 135mm CW.

• All berried females must be returned to the water within 5 minutes of the crab pot being pulled.

• The number of Exemptions granted for access to this fishery is limited to two.

• Pot design must be approved by FDWA researchers. Pots are designed to enable the escape of none target species and juvenile and undersized crabs (to approximately 120mm).

• A total of 600 traps are currently authorised to operate in the fishery.


It is likely that poor recruitment and decreased catch rates would be more attributable to environmental factors rather than commercial fishing effort. This may become more apparent at the conclusion of the current research projects underway. A predictive catch model, similar to the west coast rock lobster fishery, is not an expected outcome, at least in the short to medium term. Natural characteristics of blue swimmer crabs such as the high fecundity, size at sexual maturity and short life span will continue to provide long-term security in recruitment to the fishery. The long-term sustainability of blue swimmer crab stocks is not considered to be at risk. Actions if performance limit is exceeded: As the fishery is still in the developmental phase acceptable catch ranges are yet to be determined, however catch data are reviewed on an annual basis and any significant, increase or decrease in catch or catch rate will trigger FDWA to look more closely at exploitation rates. If the change is not explained by environmental variations or a peculiarity of industry dynamics and behaviour, then strategies that offer further protection to the breeding stock will be considered. The options in this regard include a reduction in trap numbers or the introduction of seasonal closures. These can be implemented within a season or prior to the beginning of the next season. Comments and Actions

None. External Drivers

The factor most likely to affect harvestable biomass is decreased recruitment to the fishery due to environmental conditions.

BY-PRODUCTS

Coral Crabs Rationale for Inclusion:

Under the exemptions for the NDBSCF coral crabs may be landed as by-product. Coral crabs (Charybdis cruciata) are generally found in marine coastal waters on a range of bottom types including mud, sand, rock and seagrasses in depths of up to 60m (Jones and Morgan, 2002). While they are not the primary targets of the blue swimmer crab fishery their abundance at certain times of the year, especially in the northern regions of the fishery, means they are landed as bycatch. Coral crabs are frequently marketed but only in small quantities. Reported catches from NDBSCF are low


ERA Risk Rating: Impact on breeding stock Likelihood: Occasional, Consequence: Negligible Risk Rating: Negligible Only small catches of coral crabs have been reported. Given the vast area of coast over which this species occurs, along with their short life cycle and high fecundity (Sarada, 1998), the fishery is likely to be having only a Negligible impact. Sand Crabs Rationale for Inclusion:

Under the exemptions for the NDBSCF sand crabs may be landed as by-product, however to date there have been no recorded catches of sand crabs in NDBSCF. Sand crabs distributed across southern Australia. They are common on surf beaches and in sandy bays and inlets they also occur off shore to depths of 100 m (Jones and Morgan, 2002). ERA Risk Rating: Impact on breeding stock Likelihood: Possible, Consequence: Negligible Risk Rating: Negligible Their life history and wide distribution coupled with nil recorded catches warrants a Negligible risk rating for sand crabs. NON-RETAINED SPECIES Captured in Traps

Finfish Rationale for Inclusion:

Low numbers of finfish are infrequently captured in crab pots. Species captured include Northwest blowfish (Lagocephalus spp), NW snapper (Lethrinus spp), Butterfish (pentapod spp), leather jackets and boxfish. ERA Risk Rating: Impact on breeding stock Likelihood: Possible, Consequence: Negligible Risk Rating: Negligible Traps are purpose designed to minimise the capture of non-target species and are a very inefficient way to capture fish. The majority of fish that enter the pots are able to escape through the entrance gaps in the side of the pot. If they have not already escaped while the pots were soaking they can also escape as the pot is hauled to the surface. Moreover, crab fishers are not permitted to retain any fish species caught in


pots. The low number of fish caught and returned by crab fishers is considered to pose a negligible risk to the breeding stocks of these species. Octopus Rationale for Inclusion:

Anecdotal evidence from fishers indicates that in shallow waters octopuses are regularly caught in low numbers. However, fishers are not permitted to retain any octopus landed in crab pots. ERA Risk Rating: Impact on breeding stock Likelihood: Unlikely, Consequence: Negligible Risk Rating: Negligible Crab pots are a very inefficient way to catch octopus, pots are purpose designed to minimise the capture of non-target species. The majority of octopus that enter the pots are able to escape through the entrance gaps in the side of the pot as the pot is hauled to the surface if they have not already escaped while the pot was soaking. The low number of octopus caught and returned by crab fishers (most of these should survive) is considered to pose a Negligible risk to the breeding stock of octopus. Other Crabs Rationale for Inclusion:

Various other species of shallow water crabs are infrequently caught in small numbers by commercial blue swimmer crab fishers. It is prohibited to retain any species of crab, other than blue swimmer, coral and sand crabs. All other crab species captured must be returned to the water unharmed. ERA Risk Rating: Impact on breeding stock Likelihood: Possible, Consequence: Negligible Risk Rating: Negligible Quantities of other species of crabs caught are insignificant and all specimens are returned to the water immediately. These are all expected to survive; therefore it is considered that their capture would have a negligible impact on the breeding stocks of those species.


Starfish Rationale for Inclusion:

Various species of starfish are infrequently caught in small numbers by commercial blue swimmer crab fishers. It is prohibited to retain any species starfish, all specimens captured must be returned to the water unharmed. ERA Risk Rating: Impact on breeding stock Likelihood: Possible, Consequence: Negligible Risk Rating: Negligible Quantities of starfish caught are insignificant and all specimens are returned to the water immediately. Therefore it is considered that their capture would have a negligible impact on the breeding stocks of those species. Direct Interaction but not Captured in Traps

Dugongs Rationale for Inclusion:

Dugongs are relatively common in the inshore protected waters of the Pilbara where they feed on seagrass sandflats, they are also known to occasionally venture further offshore to deeper waters. There are no reports of dugongs becoming entangled within the fishing gear of the NDBSCF (D Coughran 2005, CALM pers. comm., 30 August). Also, while animals sometimes present with scars, there are no reports or known cases of dugongs being injured or run over by boats from the NDBSCF fishery (D Coughran 2005, CALM pers. comm., 7 September). ERA Risk Rating: Impact on breeding stock Likelihood: Possible, Consequence: Negligible Risk Rating: Negligible Reports from the whole of the WA did not record a single incidence where crab trap fishing gear interfered with dugongs (D. Coughran 2005, Department of Conservation and Land Management, Perth Office, pers. comm., 7 September). The lack of any dugong interactions with crab boats and fishing gear justifies the negligible risk rating for this item.


Manta Rays Rationale for Inclusion:

Manta rays are pelagic, unable to swim backwards and, with distinctive long cephalic lobes, there is the possibility that these species could become entangled in the ropes associated with crap traps. ERA Risk Rating: Impact on breeding stock Likelihood: Possible, Consequence: Negligible Risk Rating: Negligible Reports from the whole of the WA did not record a single incidence where crab trap fishing gear interfered with manta rays (D. Coughran 2005, Department of Conservation and Land Management, Perth Office, pers. comm., 07 September). Therefore it is considered that interactions, whilst possible are likely to have a negligible impact on the breeding stocks of these species. Seabirds Rationale for Inclusion:

Various seabirds are regularly seen following or lingering near fishing boats. All seabirds are protected species; direct interactions with crab boats are usually based on the birds seeking bait and by catch discards. The only bird – related issue of potential significance that has been identified is the possible capture of pied cormorants (Phalacrocorax varius). These birds will dive fish and have been known to poach from lobster and crab traps. It is possible that in doing so the birds can get their necks lodged in the exit holes of the traps. ERA Risk Rating: Impact on breeding stock Likelihood: Possible, Consequence: Negligible Risk Rating: Negligible Incidences of cormorants becoming trapped in gear are unknown in the NDBSCF but have been reported in other trap based fisheries. The numbers of pied cormorants in the NDBSCF is low and the fishers (and number of traps) are relatively few, therefore the chance of entrapment is low (Dr N Dunlop, 2005 Conservation council WA, pers comm., 09 September). While possible, this is likely to be of negligible risk to pied cormorant breeding stocks.


Turtles Rationale for Inclusion:

Five types of sea turtles are found on the west coast, these are the Flatback (Natator depressus), the Green (Chelonia mydas), the Hawkesbill (Eretmochylys imbricata), the Leatherback (Dermochelys coriacea) and the Loggerhead (Caretta caretta). A number of these species are listed as "vulnerable" in the Commonwealth EPBC Act and "Special Protected Fauna" under WA Legislation, and the loggerhead turtle (Caretta caretta) also a protected species under the provisions of the WA Wildlife Conservation Act 1950. All forms of mortality need to be minimized for the turtles. The main risk of interactions between fishing operations and turtles in the NDBSCF would be from boat strikes and entanglement in ropes and lines, not from being caught in traps. The occasional (<1 per year) entanglement of turtles in pot lines (R. Prince, Department of Conservation and Land Management, Perth Office, pers. comm.) indicates a low risk associated with using crab fishing gear. There is a very low chance of these vessels or their equipment encountering turtle species. ERA Risk Rating: Impact on breeding stock Likelihood: Unlikely, Consequence: Negligible Risk Rating: Negligible Both species are long ranging foragers with large residence areas found offshore throughout the south coast to south Australia. The Leatherback turtle breeds in very specific regions in the tropics (SE Asia, Indonesian archipelago, Malaysia Peninsula) consequently these animals make migratory journeys of thousands of kilometres. The loggerhead turtle is commonly found, and breeds on sandy beaches in a defined area between Shark Bay and Exmouth. Distribution of the Shark Bay population is not well known but when not breeding these turtles range out to sea. Crabs form part of the diet of the Loggerhead (Caretta caretta) (Dr R Prince, Department of Conservation and Land Management (CALM), Perth office, pers. comm.) but they are one of many food sources (www.deh.gov.au/coasts/species/turtles/loggerheads.html.) Loggerhead turtles are reported in Nickol Bay (central to the NDBSCF) on a very low frequency (F. Stanley, CALM, Karratha office, pers. comm.). The main risk of interactions between fishing operations and turtles in the NDBSCF are from boat strikes and entanglement in ropes and lines, not from being caught in pots. There have been no reports of boat strikes or entanglements of turtles in the NDBSCF therefore it is considered that this fishery has a negligible impact on the breeding stock of turtles.


Whales and Dolphins Rationale for Inclusion:

Two species of whales are regularly observed migrating along the coast of Western Australia, the Humpback whale (Megaptera novaengliae) and the Southern Right Whale (Eubalaena australis). There are no reports of whales becoming entangled within the fishing gear of the NDBSCF (D. Coughran 2005, pers. comm., August 30). Two species of dolphins, the Bottlenose dolphin (Tursiops truncatus) and the Common dolphin (Delphinus delphis) have been reported following crab boats in other similar fisheries, possibly feeding on discarded bait. In addition, reports from the whole of the WA did not record a single incidence where crab trap fishing gear interfered with dolphins (D. Coughran, Department of Conservation and Land Management, Perth Office, pers. comm.). ERA Risk Rating: Impact on breeding stock Likelihood: Rare, Consequence: Negligible Risk Rating: Negligible Anecdotal evidence from blue swimmer crab fishers suggests that there have been no interactions with whales or dolphins in this fishery. From this limited data it appears that the risk of incidence are negligible. The lack of any whale interactions attributable to crab fishing gear justifies the negligible risk rating for this item. GENERAL ENVIRONMENT REMOVAL OF/DAMAGE TO ORGANISMS

Impacts From Ghost Fishing Rationale for Inclusion:

The pots used for capturing the blue swimmer crabs may be lost during fishing operations. It is necessary to assess the possibility of any lost pots continuing to fish. ERA Risk Rating: Impact on breeding stock Likelihood: Possible, Consequence: Negligible Risk Rating: Negligible The gear used in this fishery generates minimal non-retained species and the design of the traps is such that they do not ‘ghost fish’ if lost. The number of commercial pots lost throughout the fishery each season is unknown but is likely to be low. Anecdotal evidence and observations by DFWA staff clearly shows that blue swimmer crabs (and other large animals) are rarely seen in any type of pot without bait, showing that


animals are able to escape from the trap if given enough time. The fact that there is no retention of animals in pots that are not baited, justifies the negligible risk rating. Impacts to Benthic Biota – Sand Rationale for Inclusion:

Sand and associated biota are not brought to the surface in commercial blue swimmer crab pots. The mesh used on traps is sufficiently large to allow the escape of any sand dwelling macrobenthos. However, some macrobenthos may be directly impacted upon when pots are placed on the benthos. ERA Risk Rating: Likelihood: Low, Consequence: Negligible Risk Rating: Negligible Fishing with traps results in limited habitat disturbance, with only minor dragging of traps on the bottom during trap retrieval. This suggests that the impact on these habitats would be negligible. Impacts to Benthic Biota – Seagrass Rationale for Inclusion:

Occasionally pots are set in seagrass areas. The impact on these habitats from this activity needs to be assessed. ERA Risk Rating: Likelihood: Possible, Consequence: Negligible Risk Rating: Negligible Fishing with traps results in limited habitat disturbance, with only minor dragging of traps on the bottom during trap retrieval. The occasional presence of only small amounts of seagrass in the pots after hauling suggests that the impact on this habitat type is most likely to be negligible. Impacts to Fishing Trophic Level Rationale for Inclusion:

All fisheries need to assess the possibility that they may impact on community structure by the removal of significant quantities of one or more species. This could affect lower trophic levels (in this case the prey of blue swimmer crabs) and higher trophic levels (in this case other animals preying on blue swimmer crabs).


ERA Risk Rating: Likelihood: Unlikely, Consequence: Negligible Risk Rating: Negligible The risk rating has in this instance been accorded as negligible rating. Blue swimmer crabs are scavengers and are therefore not likely to be involved in interactions that structure these communities. Secondary food chain effects are likely to be minimal as there is an abundance of size classes under the legal size limit of 135mm CW, which is effectively renewed annually, hence the commercial take of crabs represents a relatively small portion of the biomass of crabs in the area. Addition/movement of biological material

Discarding/Provisioning Rationale for Inclusion:

There are some non-retained species in this fishery which when discarded might be considered to provide a food source to other species either following the vessel (e.g. sharks, dolphins seabirds) or on the bottom (e.g. sharks, finfish and invertebrates). ERA Risk Rating: Likelihood: Unlikely, Consequence: Negligible Risk Rating: Negligible As has already been noted, the amount of finfish and invertebrates that are discarded by this fishery is small. Traps are normally left soaking for several days between hauls and little bait remains when the traps are brought to the surface. It is considered that the small quantities of discarded catch and bait would have an insignificant impact on marine foodwebs; thereby justifying the negligible risk rating that was accorded this item. OTHER IMPACTS – WATER QUALITY

Debris Rationale for Inclusion:

There is the potential for lost pots, discarded bait boxes and bands and other flotsam to impact on water quality. ERA Risk Rating: Likelihood: Remote, Consequence: Negligible Risk Rating: Negligible There is a general code of practice among crab fishers to return packaging and garbage back to the wharf. Waste disposal bins are located at all points where commercial boats tie up. Fishers are aware of the related public perceptions and sensitivities.

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