Salini et al., 2007: 

"Project Objectives

1. Establishment of long-term collection of catch composition data from target shark fisheries in northern Australia (NT Joint Authority Shark Fishery, NT Coastal Net Fishery, Queensland Joint Authority Shark Fishery, Queensland N9 Shark Fishery, WA Joint Authority Shark Fishery, WA North Coast Shark Fishery, Queensland East Coast Net Fishery), in order to improve stock assessments.
2. To determine the appropriate management scale for the target species of northern Australian shark fisheries, by examining the degree to which stocks are shared across northern Australia and with Indonesia.
3. To evaluate the effect of gill net fishing on northern chondrichthyans, by determining bycatch composition (Queensland N3 Net Fishery, Queensland East Coast Gill Net Fishery, NT Barramundi Fishery, WA Kimberley Gillnet and Barramundi Fishery).
4. To derive estimates of biological parameters to assess the status of sawfish populations; age structure, reproduction and growth.
5. To re-evaluate the risk assessment of northern chondrichthyans (undertaken in the EA project), based on the new information collected above. This risk assessment will be compatible with the one undertaken in application FRDC 2002/033 (PI Terry Walker) in line with the NPOA-Shark priority for a national approach to risk assessment for chondrichthyans.

The importance of the shark fishery has been enhanced by the high public profile of sharks, the sensitivities and value of the shark fin trade and the explosion in illegal foreign shark fishing across northern Australia (also driven by high fin values). The Illegal, Unreported, Unregulated (IUU) shark issue has largely developed within the course of this project and for this reason resource managers need the latest information on the species composition and catch rates for, target shark fisheries, fisheries that take shark as bycatch (mackerel fisheries, barramundi gill net fishers, trawl fisheries) and illegal (foreign) shark fishing. The consequence of the high value of shark fins means that the effort directed towards shark by Australian and IUU fishers, has increased significantly in recent years. Australia has a responsibility to manage the north Australian shark fishery, and other fisheries that take sharks, in an ecologically sustainable way. This responsibility is driven by several factors, including legal obligations that are linked to the National Plan of Action (NPOA) for the Conservation and Management of Sharks (administered by Department of Agriculture, Forestry and Fisheries, DAFF), the general public and conservation groups.

Since sharks tend to be slower growing and have a lower productivity (reproductive potential) than fin fish, there is concern for their ability to withstand increasing fishing pressure. In order to provide information useful to shark fishery managers, this project set out to:

1. provide data to enable these fisheries to improve stock assessments
2. ensure management is at the appropriate scale for stocks
3. address some of the EPBC Act guidelines and
4. align with the National Plan of Action for the Conservation and Management of Sharks.

The establishment of shark fishery observers in WA, NT and Queensland was successful in terms of
the target shark fisheries in each jurisdiction. In the barramundi fisheries (shark bycatch fisheries), there was limited success in gaining observer time with fishers. Future effort to monitor shark bycatch fisheries such as the barramundi fishery, may require cooperative log-book changes to improve the recording of shark bycatch. This outcome was to be included as part of a future FRDC project (unsuccessful proposal) to help Qld and NT jurisdictions introduce the improved log books.

Establishing shark fishery observers was undertaken slightly differently in each jurisdiction. WA Fisheries were able to incorporate an existing shark researcher (Justin Chidlow) for the duration of the observing schedule, as was the case in Queensland Fisheries where the project phase 1 observer continued in that role (Stirling Peverell). Keeping an observer in the NT shark fishery was more challenging with three observers filling the role. The biological data collected by observers was less than expected and remains a limiting factor in the risk assessment calculations for the less abundant species.

Understanding the management scale based on genetic stock structure of the major target species, C. sorrah and C. tilstoni, was achieved using mtDNA and nuclear DNA (microsatellites) procedures. These revealed that Australian  and Indonesian caught C. sorrah (spot-tail shark) were separate from each other, although both species showed no genetic separation across northern Australia and the east coast. This reflects their bentho-pelagic feeding behaviour and high mobility, although C. tilstoni are not recorded from Indonesia waters and are restricted to northern Australia. This implies that uniform management of this species across jurisdictions is needed for sustainable exploitation.

An understanding of the status of sawfish in north Australian waters was enhanced by records from WA, NT and Queensland, although records were less than anticipated. However, small advances in our understanding of their distribution/habitat were made from location of capture data. The main problem in determining trends in sawfish abundance and obtaining biological data was the rarity of sawfish capture (or reporting) in commercial operations. The difficulty in obtaining independent bycatch records from inshore gill netters such as barramundi fishers was reflected in the lack of sawfish information from these fisheries. Increased biological information was obtained for all four species although life cycle parameters for age and growth were compromised by a lack of large specimens and a lack of validation of ageing data. Their high vulnerability to gill nets and trawling makes further research on their biology and habitat use of paramount importance, if shark fisheries are to mitigate against the threat to sawfish. More data on the habitat utilisation and long term movement patterns are required to mitigate the effects of fishing. Fishery awareness of project research helped stimulate proactive measures to avoid sawfish interactions and to elect to release live sawfish as a ‘Code of Practice’ measure.

Data on fishery specific species composition as well as new data on the biology of some species were used to update the risk assessment. The original risk assessment methodology was modified to better suit available data and take into account the range of methods (gear) used to capture elasmobranchs. Comparisons between the risk assessment methodology used by Terry Walker (FRDC project 2002/033) and those developed in this project were made to determine the best approach for northern Australian elasmobranchs. The risk was evaluated on a per fishery basis and a cumulative Risk Assessment over all fisheries. This revealed up to 14 high risk species, with susceptibility to gill nets and low productivity the major factors contributing to their ‘high risk’ status. These included sawfishes (Pristis clavata, P. microdon, P. zijsron), giant shovelnose ray (Rhinobatos typus), shark ray (Rhina ancylostoma), speartooth sharks (Glyphis sp. A, Glyphis sp. C), the great hammerhead (Sphyrna mokarran), the lemon shark (Negaprion acutidens), Pig eye (Carcharhinus amboinensis) and three whaler species (C. brevipinna, C. leucas, C. limbatus).

Susceptibility of shark species in the:

East Coast Net fishery (ECN)
Approximately 25 species were least likely to be sustainable in the ECN fishery (Figure 6.5-7). Of these, 14 species had susceptibility and recovery ranks above 2.33 and were the least sustainable species in this fishery. These species include C. amboinensis, C. brevipinna, C. leucas, C. limbatus, C. tilstoni, Glyphis sp. A, Negaprion acutidens, Pristis zijsron, P. microdon, S. mokarran. Eleven species had a susceptibility rank above 2.33 and a recovery rank between 1.66 and 2.33 and were also least likely to be sustainable. These species include Carcharhinus amblyrhynchoides, C. cautus, C. melanopterus, C. fitzroyensis, Eusphyra blochii and Rhynchobatus australiae. 

The following individual fisheries are briefly discussed due to their importance in terms of the size of the fishery, or interactions with threatened and protected species.

ECN
Anoxypristis cuspidata has a high susceptibility rank in this fishery and should also be closely monitored due to the fact that population of all species of sawfish have declined along the east coast of Australia in the past 20 years. Species such as C. amblyrhynchoides, C. cautus, E. blochii and R. australiae that have a high susceptibility rank and mid-range recovery ranking are likely to be at high risk from the ECN fishery due to high amount of fishing effort in this fishery (13 000 days when elasmobranchs was recorded in the catch in 2003) combined with the diversity of habitat and depth fished."

 

 

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Citation and/or URL

Salini, J., McCauley, R., Blaber, S., Buckworth, R., Chidlow, J., Gribble, N., Ovenden, J., Peverell, S., Pillans, R., Stevens, J., Stobutzki, I., Tarca, C. and Walker, T. 2007, Northern Australian sharks and rays: the sustainability of target and bycatch species (phase 2). Report to the Fisheries Research and Development Corporation (project no. 2002/064), Canberra, p. 166.

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Spatial Coverage

Whole GBR (+ Northern Australia) 

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Temporal Coverage

Whole project 2002 - 2005

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Update Frequency

Not applicable 

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Other Information

None