Knowledge of the stock structure and migration patterns is fundamental to ensuring effective stock assessment and management of a fishery. While this knowledge is scanty for many Commonwealth fisheries, swordfish structure and movements are particularly poorly known. The stock harvested by the ETBF is locally depleted, suggesting population structure, but there are no direct data on movement or distribution available. Parameterizing a model of movement for swordfish would clarify the stock structure and provide a mechanism for incorporating their movements into spatial management or assessment models.

The recent Ministerial Directive to AFMA has highlighted the lack of knowledge regarding swordfish. Key initiatives in the directive are 1) develop harvest strategies for its fisheries to ensure sustainable management; 2) recover overfished stocks; and 3) end overfishing on stocks. Furthermore, the directive urges AFMA to move to spatial management. Critical to the design of harvest strategies, determination of stock status, and development of spatial management measures is a sound knowledge of the connectivity between stocks fished locally and in other parts of the Pacific basin. In order to ensure equity in limitations due to management arrangements, Australia will need to pursue policies that ensure other nations protect shared stocks within the context of the Western Central Pacific Fisheries Commission - requiring clear evidence of the amount of movement between locally and regionally harvested stocks and empirically validated assessment models.

The March 2005 AFMA/ComFRAB Research Gap Analysis and Priority Setting Workshop, held jointly by AFMA and ComFRAB underlined the needs outlined above for swordfish in the ETBF specifically – identifying both spatial management measures to rectify the localized depletion and provision of science and policy advice into the WCPFC. The ETBF research priorities and FRDC’s strategic challenges both identify these same issues, as discussed in the Background section.

The biomass of tropical red snapper in northern Australian waters has been estimated at 24,000t. A conservative management trigger point has set annual harvest levels at 2,400t. Current catches are well below this level. The majority of red snapper is caught by trawl, but there is also a potential to target them in trap and dropline fisheries.

Tough fish from these fisheries are identified on occasion at the point of cooking. Currently it is not possible to identify this syndrome at the point of capture or wholesale. There is an urgent need to identify the cause of TFS to minimise impact of the syndrome on the value of the resource and enable appropriate handling methods to be implemented where applicable.

TFS is causing a huge loss of revenue from the reef fish fishery due to strong negative reaction from the end-supply chain sectors with this phenomenon reducing the overall value of this, and other species in the fishery. The magnitude of such losses was made apparent recently when one of Australia’s largest retailers cancelled a very large supply contract from a major fishery operator. Another major stakeholder in the fishery has had export orders rescinded.

Industry believes that if TFS in red snapper could be managed the current price of around $4.50/kg could be increased up to $8.00/kg, in line with other tropical snappers. This would lead to an estimated additional $3.0 M/year revenue from this species under current catch levels. If the value of this species increased, there is potential to significantly increase sustainable catch levels and subsequent return to the community.

Prawn fisheries throughout Australia are intensively fished and some have shown signs of overfishing. In some cases, the current stocks of prawns are now lower than those which would produce maximum yields. Prawn stocks can vary greatly from year to year because of environmental fluctuations and this leads to highly variable catches. Fishery managers must therefore adopt conservative harvest strategies to prevent fishers reducing stocks to dangerous levels in years when recruitment is low. However, the harvesting and processing sector tend to be on average, over-capitalised, in order to cope with years of high recruitment. Enhancement of prawn stocks through releasing juvenile prawns has the potential to reduce fluctuations in stocks. It provides a possible way of adjusting the catching and processing capacity to more stable levels of prawn stocks, which would reduce the need for over-capitalisation.

The enhancement of Australian penaeid prawn fisheries has the potential to be a useful management tool to increase fishery yields, rebuild over-exploited stocks, and reduce fluctuations in catch due to variable recruitment. It also has the ability to improve the management of fisheries by collecting more precise information about the biological characteristics of the stock (e.g. survival and growth, production in nursery grounds, migration pathways and factors affecting fluctuation in populations). For stock enhancement to be successful, the biology and ecology of the target animal must be thoroughly understood (including the production of the postlarvae/juveniles, environmental requirements, carrying capacity, and all factors that contribute to mortality), and methods must be available to monitor and assess the success of the releases. Much ecological information for stock enhancement is now available for many commercially important species of penaeid prawn in Australia, and novel approaches to tagging prawns (e.g. stable isotopes, rare alleles and reporter genes), release strategies, and assessment of carrying capacity are being developed.

Most of the preliminary assessments of the costs and benefits of prawn stock enhancement in Australia have not assessed a particular fishery or region in detail – they have to some extent developed generic models. For our knowledge on how to enhance prawn stocks in Australia to progress further, it is essential to develop, apply and refine bioeconomic models to a specific region and fishery. For the reasons outlined above (see background), the Exmouth Gulf Prawn Fishery is an ideal location to focus on applying the concepts and the simple model that have been developed from different studies around Australia. The much more intensive study outlined in this proposal will also help to evaluate enhancement projects for other prawn fisheries around Australia.

The beneficiaries of stock enhancement would be expected to contribute to the costs of research and monitoring, and ultimately pay for the enhancement. Therefore, stock enhancement must be cost-effective and a cost-benefit analysis using a bioeconomic model, is an essential part of any enhancement project. Bioeconomic models need to be developed in the early stage of the feasibility study. If the outcomes are favourable for enhancing tiger prawns in Exmouth Gulf, it will be used to optimise the design and management of the trial enhancement program proposed for Stage 2 of the full project.