Tropical reef fish species are popular targets by both the commercial and recreational fishing sectors and are increasingly becoming the focus in developing indigenous fisheries. They are highly prone to overexploitation because of their vulnerable biology, aggregative nature and susceptibility to barotrauma related injuries upon release. In the Northern Territory (NT), these issues have resulted in the substantial declines of key reef species around population centres and managers have been unable to apply appropriate arrangements due to a lack of knowledge on the stock structure, unknown levels of recreational harvest and contested resource ownership and access rights. It is clear that the knowledge gap on stock structure needs to be filled to move towards the spatial management needed to ensure the sustainability of the reef fish resources as well as their optimal allocation amongst sectors.
However, the exploitation of reef fish in remote areas of the NT is increasing due to an expanding recreational fleet, new mining and gas developments placing increased population in these areas and aspirations by the indigenous sector to develop fisheries on these species. While gaining information on stock structure of key reef fish species will greatly aid the sustainable development of fisheries in this area there is still the requirement to ensure regular collection of biological data to monitor these stocks. The most efficient method of obtaining this information is to train indigenous rangers/community members by developing an appropriately certified course. By underpinning the course with the stock structure component of this project, students will also receive skills to assist with co-management and developing sustainable indigenous fisheries.
This project addresses the number one NTFRAB research priority on reef fish biology as well as NT and cross-jurisdictional priorities on indigenous development.

The 1999-2003 Northern Territory Strategic R&D Plan in considering catch rates, current levels of exploitation and management requirements, ranked NT Coastal Line Fishery research as one of highest priority. The most recent revision of this plan further clarifies these concerns and clearly identifies that "Harvesting of fish and other aquatic resources can only be sustainable if the long-term rate of harvest does not exceed the long-term rate of replacement to the stock(s). Increasing catches and target fishing evident for black jewfish and high exploitation of spawning aggregations may render the stocks unsustainable. In view of the above, re-commencement of research on coastal fisheries is considered a high priority for the next 5 years" (NT Strategic Plan for R&D 2002-06). Worldwide experience in managing aggregating species indicates that they are extremely vulnerable to overfishing.

The Coastal Line Fishery (CLF) logbook data and anecdotal information from fishers provides evidence of target fishing on black jewfish aggregations in NT waters. Significant changes in the CLF catch composition have occurred over a short period and the increase in total catch can be directly attributed to the increased catch of black jewfish. Over the period 1990-2001 the percent contribution of black jewfish to the total catch has increased from 11% to 77%. Once a multi-species fishery the CLF is now primarily a black jewfish fishery with a reef fish bycatch. In 1999 the CLF black jewfish catch reached 58 tonnes increasing 93% in just twelve months to 101 tonnes in 2000. Catch per unit effort (CPUE) for the same period increased just 27%. Black jewfish catch continues to increase, reaching 136 tonnes in 2002 and 167 tonnes in 2003, while CPUE has remained stable.

Of great concern is that these changes in black jewfish catch have occurred while considerable latent effort exists in this fishery. In 2002 only 27 of the 58 (46%) CLF licences issued, actively fished and of these just seven were responsible for 80% of the total catch. Increasing returns to a small group of fishers has created much interest in this fishery with new vessels and fishers from other fisheries preparing to fish for jewfish. The potential for increased effort in this fishery is high.

The 1995 the NT recreational harvest of Black Jewfish was estimated at 232 tonnes (FISHCOUNT) approximately six times the 1995 commercial catch (32 tonnes). The 2000 National Recreational and Indigenous Fishing Survey indicates that the NT recreational catch of black jewfish has reduced by approximately 25% to around 140 tonnes in 2000 (Henry and Lyle 2003).

Anecdotal reports from both commercial and recreational fishers suggesting a decline in the average size of black jewfish in the NT. Re-commencement of on-board monitoring of the commercial fishery is a key component of this project as such data is considered critical in assessing the impact of fishing on these aggregations.

Analysis of commercial catch and effort data suggests that the commercial fleet is moving from one aggregation to another, as aggregations are depleted and the same pattern of a more localised nature is highly likely for the recreational fishery.

The Aquatic Resource Management Section of the NT Fisheries Group has an urgent need for information on the make up of black jewfish aggregations in the NT. Information such as: Why do the aggregations occur? Why do they occur at particular sites? What is the extent and timing of movements between aggregations? Where do the fish go when not in aggregations? This project will address these questions directly. It will also provide leads for broader and more complex questions such as: what proportion of the stock is vulnerable in aggregations; to what extent does protection of one site affect fish at other sites; how mobile might sites be etc.

The current paucity of information is a critical impediment to the ability of the Fisheries Group to provide adequate protection of the Northern Territory’s black jewfish stocks and associated fisheries.