Stock assessment of the Heard Island and McDonald Islands (HIMI) toothfish fishery currently uses an integrated population model. This model relies on estimates of parameters that predict the productivity of the population e.g. growth rates, mortality rates, recruitment rates and spawning stock biomass. Advice on sustainable catch limits for toothfish use decision rules developed by CCAMLR, which seek to ensure that there is sufficient escapement of spawning biomass to ensure the productivity of the stock is not reduced by fishing. Hence stock assessments are very sensitive to estimates of size at maturity, as this determines the proportion of the population that is mature and contributing to the spawning stock. Currently, the size and age at which toothfish mature at HIMI is unknown. The estimate used in the model is derived from spawning fish sampled in the French EEZ around Kerguelen Island. There are clear linkages between the French and Australian stocks, however the differing fishing history and environment in the French EEZ means using the French data for HIMI toothfish may create bias in the assessment. With demersal long lining commencing in 2003 and fishing of deeper slope waters in recent years, spawning toothfish have been captured by demersal longlines for the first time in 2009 and again in July 2010, and hence an opportunity now exists to collect data on spawning activity in the Australian EEZ for the first time.
The urgency of this project is high, due to the need for understanding of the spawning dynamics to assist in forthcoming discussions with France, scheduled for mid 2011, as to how complementary harvest strategies can be developed for toothfish across the region. Establishing the existence and extent of a spawning stock in the Australian EEZ will be important in ensuring Australia gets fair and equitable access to this resource.

1) The ecosystem effects of fishing need to be understood in order to work towards an EBM model for the Spencer Gulf. The South Australian government’s Marine Manager’s Forum has identified Spencer Gulf as the first area in SA for the development of a marine management plan. Better information on impacts of fishing will reduce the reliance of managers on the precautionary principle in developing management plans.
2) The important results from FRDC project 98/225: Prawn fishery by-catch and discards: fates and consequences for a marine ecosystem, are an understanding of the major components of the food chain in the trawled areas of the Gulf and the identification of the major scavenger groups on discarded by-catch. There is a need to obtain data on population impacts in order to develop trophic dynamic models.
3) A prerequisite for energy-flow models is population data outlining life history parameters, growth, migration and immigration and standing stock of, in principle, all the major species.
4) Previous research by this investigator shows that the quantitatively important scavengers on discarded by-catch in the Spencer Gulf prawn fishery are Degens leatherjackets, sealice (non-parasitic highly aggressive isopods and amphiopods), blue crabs, large stingrays and Port Jackson sharks. The effects of discarded by-catch on the population structure of these species need to be understood with the aim of developing an ecosystem model.
5) The impact of fishing on marine ecosystems (target and by-catch) on sharks, skates and rays is a world-wide problem (Stevens et al. 2000). 50% of the global catch is taken as by-catch. The catch of non-target species can have an impact at the population and ecosystem levels, particularly the removal of top predators. Elasmobranchs are at the top of the food chain in the Spencer Gulf and are important by-catch in the prawn fishery. The ecosystem level effects of fishing on the populations of these species are unknown. Discarded by-catch is susceptible to mortality. This mortality, including sub-lethal effects and post discard mortality, needs to be measured in order to predict ecosystem effects.
6) To adopt the principle of ecological sustainability in the prawn fishery, change negative public perceptions of environmental impacts, and improve fishing practices.
7) To enhance the research capacity in environmental research with emphasis on biological resource utilisation.
(Stevens, J.D., Bonfil, R., Dulvy, N.K. & P.A. Walker 2000. The effects of fishing on sharks, rays, and chimaeras (chondrichthyans), and the implications for marine ecosystems. ICES J. Mar. Sci. 57: 476-494.)

In 2005, the Ministerial Directive to AFMA included the requirement to develop harvest strategies for all Commonwealth fisheries. To determine target reference points for albacore in the ETBF consistent with the Harvest Strategy Policy, data are required on several biological parameters such as size/age-at-maturity, growth rates, fecundity and mortality (Campbell et al., 2007). Furthermore, to estimate spawner-per-recruit reference points which are used as proxies for MSY-based reference points, the agreed harvest strategy for the ETBF specifically requires estimates of size-at-maturity and mortality. However, the harvest strategy currently uses life-history parameters taken from SPC’s regional stock assessment, which in turn are either uncertain or assumed (Hoyle, 2008). For example, growth parameters are based on less reliable length-frequency and vertebrae ring counts, and the maturity schedule is based on a study of North Pacific albacore from the 1950s. There are no reliable estimates of fecundity or spawning frequency for any albacore stock. Thus, the WCPFC-SC has identified the need to improve our understanding of life-history parameters and stock assessment for albacore as a high priority.

In 2008, the stock assessment model for South Pacific albacore was revised and "the cumulative effect of these changes was to reduce the biomass estimates and raise the fishing mortality estimates compared to previous assessments" (Hoyle et al., 2008). Although there is still significant uncertainty in the model, the assessment provided a more pessimistic view of stock size and MSY (1/3 of the volume) compared to the 2006 assessments. Such a significant change highlights the requirement for accurate assessments of albacore and the ensuing need for revised biological data.

In 2008, the ETMAC called for research to determine biological characters of albacore as a priority project (project-7). The current proposal addresses this need and will maximize the value of complimentary studies being undertaken at SPC.