National and international fisheries management policies require that the exploitation of fisheries resources should be conducted in a manner consistent with the principles of ecologically sustainable development, in particular the need to consider the impact of fishing activities on non-target species and the long term sustainability of the marine environment. AFMA’s Ecological Risk Management (ERM) framework details a process for assessing and progressively addressing the impacts that fisheries’ activities have on marine ecosystems based on the ecological risk assessment for the effect of fishing (ERAEF). The ERAEF, which assesses species-by-species impacts of fishing on all species encountering a particular fishing activity, is perhaps the most comprehensive assessment method supporting ecosystem-based fisheries management currently available. This method has been applied to the majority of Commonwealth fisheries, however, these assessments only take account of risk to individual species from individual Commonwealth fisheries or sub-fisheries. It is the cumulative impact from all fisheries/sub-fisheries on each individual species that determines the species’ overall sustainability. However, the cumulative risk to a species across all Commonwealth and state-managed fisheries in which it is captured cannot currently be quantified at level 2 in ERAEF, the productivity-susceptibility assessment (PSA), nor at level 3 sustainability assessment for fishing effect (SAFE) for most fisheries. A recent study shows potentially very high levels of overlap for many species across several Commonwealth fisheries, and some state-based fishery assessments have also highlighted the importance of extending the ERAEF toolbox to include a cumulative risk assessment tool. There is an urgent need to develop methods and conduct ecological risk assessments on the cumulative impact of all species encountered by multiple fisheries.

Stock assessments are an essential part of sustainable fisheries practices that not only safeguard the environment, but the industry as well. Natural resources sustainability is the most important of four programs outlined in FRDC’s new research and development plan for 2000 and beyond. Research on stock assessment methods is one of ten strategies outlined in the sustainability program. Our project, that aims to validate an innovative and economical addition to stock assessment methods, is a practical way to achieve one of FRDC’s strategic goals.

Stock assessment is hugely important, but is also very expensive and has a critical need for improved accuracy and precision. The Research and Environment Committee of NORMAC estimates that stock assessment of the northern prawn fishery costs over $700,000 per year. The refinements proposed to stock assessment methodology as a result of this project may significantly reduce these costs, perhaps down to $100 -200,000 per year for both species of Gulf tiger prawns.

This new methodology also has the potential to increase the accuracy and precision of stock assessment estimates. As it stands, stock assessment methodology is widely recognised to have serious limitations. Catch and effort data is used as a surrogate for biomass but is known to be biased due to the aggregation behaviour of both the fishing fleet and target species. The common assumption of a relationship between spawning stock size and subsequent recruitment is dogma that has never been rigorously tested. The great strength of this project is that genetic estimates of spawning stock size will be made that are completely independent of equivalent conventional estimates.

This project addresses an issue which has been debated for some time in the Tasmanian abalone fishery and is discussed at most industry and management meetings. It is an issue that affects the size of the harvest, the price of product and the productivity of the stock. Thus there is a need to resolve this management debate and there is also a need to explore these ideas for higher production.

The project will be of greatest value for the regions of the state where growth information is limited as production is low (to put this in context, this component of the Tasmanian fishery accounts for around 1600 t of production, which is more than total production in any other state). Management issues in these locations are often hard to resolve because of lack of biological information. This project may allow management to proceed with a second-tier level of data derived from shell condition, which is far more readily obtained than tag-recapture data.

The project also addresses the need for information on density dependent growth in abalone - put simply, can production be increased by "thinning out" the stock. This is a fundamental question that is of interest for abalone stocks around Tasmania and also interstate.