With the continuing recovery in the size of Australian-based fur seal populations post-sealing, a corresponding increase in seal interactions with domestic fishing vessels is occurring and will continue. There is an urgent need to develop effective seal bycatch prevention procedures to prevent fishing operations from being severely curtailed, or closed down, under the Environment Protection and Biodiversity Conservation Act 1999.

Following the 1999 winter blue grenadier season, incidental seal mortalities emerged as a major issue that threatened the continuation of this fishery; at least that part of the fishery harvested by factory trawlers. These trawlers had successfully developed the fishery, increasing the total grenadier catch from about 3000 t in 1996 to over 9000 t in 1999. The processed value of the factory trawler catch is now around $20 million per year (ASIC 2003) at first sale. The seal deaths in 1999 resulted in significant pressure from some environmental groups to prevent factory trawlers access to this fishery in 2000. This action would have caused significant loss of income in this sector and possibly jeopardised the future participation of factory trawlers in the fishery. There is a strong need for such vessels to demonstrate that seal bycatch can be reduced by adopting appropriate fishing procedures and gears.

It is also likely that pressures will be brought to bear on the ‘wet boats’ fishing for blue grenadier and possibly the rest of the SEF trawl fleet to take measures to reduce incidental seal captures. The study by Knuckey et al. (2002) indicated seal bycatch to occur virtually across the whole multi-species trawl fishery. Some of the results of the development and testing of SEDs and other mitigation measures by the factory trawlers in the targeted ‘single-species’ fishery under this project may be transferable to other vessel operators in the wider multi-species fishery, helping them to avoid many potential operational problems and costs. Increasing the effectiveness of SEDs in both reducing seal mortalities and minimising fish losses would be an important step in helping to gain wider industry acceptance of the potential use of these devices.

Time and again, good research results have been wasted because there has been poor industry support, lack of industry consultation and a low level of effective extension of the results to grass-roots industry. Through Project 98/204, we have developed outstanding bycatch reduction results in the SETF with full industry support, high levels of consultation and an extensive extension process. Whilst all of the newsletters and videos have achieved a high level of Industry awareness of the bycatch reduction project, it is now time to promote and encourage industry uptake of the modfied codend designs. This will require hands-on work with the fishers on a one-on-one basis and further analysis of fish behaviour to reduce discards in trawl gear to a greater extent. This proposal seeks funds to support this phase of the project and continue the outstanding success of 98/204 in reducing the bycatch in SEF trawlers.

As evidence of the effective extension of the results of the current FRDC project 98/204, operators within the Great Australian Bight trawl fishery have shown keen interest in deploying modified gear to reduce bycatch in their fishery. As such, they have expressed their enthusiasm in participating in a project of this nature and wish to be included as participants within this proposal.The project budget and methods have been revised to reflect this.

Blue and spotted warehou are important species in the South East Fishery. The 2000 actual TACs for blue and spotted warehou were 1907 and 4829 tonnes, respectively. The species, however, exhibit conflicting trends. The blue warehou TAC has been reduced in recent years while that for spotted has been increased. The total blue warehou catch in 1999 was the lowest since 1986 and recent assessments indicate that the "stock" is in decline. The 2001 TAC for blue warehou has been halved to 750 t. For spotted warehou, it was concluded, at a recent stock assessment workshop, that while recruitment is variable trends in standardised CPUE indicate a relatively stable resource.

There have been no studies on the stock structure of these species in Australian waters and for management purposes both species are considered one stock. In this application, the term stock is used to refer to a management unit, that is fishing one unit does not effect another. This may or may not have a genetic significance.

Both species exhibit complex spatial variability, particularly east and west of Bass Strait. The importance of this to assessment is increasingly been realised. The most recent assessment of blue warehou is considerably more uncertain because model fits to the data are very poor, assuming a single population across the fishery, and consequently areas east and west of Bass Strait were modelled separately. However, fits of models themselves are not an adequate base for determining stock structure and there are a number of hypotheses (eg. separate east and west stocks; one stock but the recruitment rates to the east and west differ among years; migrations between east and west) that appear to be consistent with the existing information. Similarly future assessments of spotted warehou will be limited without this information. Clearly, the lack of information on stock structure and spatial dynamics will adversely effect the efficacy and acceptance of stock assessments of both species.

This proposal aims to address this issue by assessing a suite of tools to determine which can provide the most information on stock structure; genetics, morphometrics, otolith morphology and otolith microchemistry. The latter may also provide valuable insights in migratory dynamics. All these techniques can be expensive and sometimes provide ambiguous results. Consequently, the proposal is to undertake a pilot study assessing these approaches to ascertain the most useful method prior to any full study being undertaken. However, although it is a pilot study, it is hoped that the preliminary results will assist BWAG weight the hypotheses used in the modelling and hence reduce uncertainty in the assessment.