Effects of Trawling Subprogram: maximising yield and reducing discards in the South East Trawl Fishery through gear development and evaluation
Discarding is unproductive and time consuming for fishers who have to sort through the catch and when commercial fish are discarded it is also seen as a waste of a potentially valuable resource. Furthermore, whilst the effects of discarding have yet to be established at an ecosystem level, the practice attracts negative publicity for the Industry and is considered by some to be contrary to the principles of ecologically sustainable development. For these reasons, it is necessary to consider ways of reducing the level of discarding in the SEF.
An understanding of gear selectivity is essential for the effective management of any fishery. Control of gear selectivity is a pre-requisite to regulating fishing mortalities associated with total catches (retained and discarded components). Like the majority of the world's fisheries, selectivities of trawls in the SEF are regulated by means of legally defined minimum mesh sizes (currently 90 mm). There is a great potential however, to use the recent advancements in trawl technology such as different shapes and sizes of mesh panels and codends, exclusion devices and modified trawl rigging to help modify SEF trawls and improve their selectivity towards targeted species and reduce the catch of small fish that are usually discarded. Thus, an extensive range of "tools" has been developed to improve trawl gear selectivity and overcome many of the perceived problems associated with trawling. This knowledge can be applied in the SEF with the appropriate design modifications to meet the specific gear / species configurations that occur in this fishery.
There would be many benefits for SEF fishers if gear selectivity or fishing practices could be modified to maximise the yield of their catch whilst reducing the catch of unwanted fish. The problem is to develop practical solutions to the various selectivity-related problems in the SEF which will be willingly be adopted by the fishers.
It is important to note that in any fishery, the development and adoption of gear modifications to achieve certain goals, such as bycatch reduction, is a long and often tedious process. The current project is only a small step in this process. It will not, and is not expected to, solve all of the SETF bycatch problems. The results of the project will form one of the foundations upon which the SETF can exist under the principles of ecologically sustainable development.
Final report
There is increasing worldwide concern about the ecological impacts of trawling. Reports of high levels of bycatch of fish and other species, habitat degradation, bad practices, stock depletion and perceptions of wastage and negative ecological impacts continue to fuel these concerns.
Australia’s Commonwealth Trawl Sector (CTS) — previously known as the South East Trawl Fishery, or SETF — is a complex multi-species sector of the Southern and Eastern Scalefish and Shark Fishery (SESSF) operating across the shelf and upper slope waters in south eastern Australia. The SESSF caught approximately 22,000 t of fish during 2007 with a gross production valued at around $96 million during the 2006–07 financial year (Morison 2008). More than 100 species of finfish and invertebrates are routinely taken in the SESSF, supplying most of the fresh fish for markets in NSW, Victoria, Tasmania and South Australia, and some product for the export market. Onboard monitoring programs have revealed that varying, but significant levels of the catch (up to 50% by weight) are caught and discarded in the fishery. Although some commercial species are discarded, many of the discards are comprised of small fish species with little or no commercial value. Like other trawl fisheries, there is increasing concern about the ecological impacts of this bycatch in the CTS. As a consequence, the Australian Fisheries Management Authority and fishery stakeholders have implemented a Bycatch Action Plan, which aims to reduce bycatch in the fishery and ensure ecological sustainability. An important component of this Plan is a project designed to modify the trawl gear to increase the proportion of small unwanted fish that escape. This report presents the results of that research and discusses the importance of disseminating this information to key industry stakeholders and the wider community.
