Threadfins form an important component of barramundi fisheries and are likely to play a significant ecological role in northern inshore habitats. Despite their importance and the expansion of coastal fisheries, the status of the threadfin resource in most parts is unknown whereas in WA they are considered fully or over-exploited (Pember et al, 2005). This uncertainty arises from the limited understanding of threadfin biology, stock structure and a lack of available data on resource exploitation (Welch et al. 2002). The inshore net fisheries across northern Australia are currently managed separately and under vastly different management regimes. However, without knowledge of threadfin stock structure the appropriate spatial scales of management is not known. In August 2003, the Northern Australian Fisheries Management Forum (NAFM) signalled its intention to move from single jurisdiction-based fishery assessment and management towards a more integrated approach that reflected the management needs of species across their northern Australian range. Elucidation of threadfin stock structure is vital for their management at an appropriate ecosystem scale. Attending to these critical issues for threadfins will also provide a framework for addressing management of other inshore species that are fished in adjacent State and Territory waters. Consequently, this project addresses research priorities outlined by QFIRAC, the NT FRAB, Fisheries WA and Sunfish.

Industry has also expressed major concerns for the sustainability of the threadfin fisheries. These concerns are based on fishers’ personal experience’s, whereby large concentrations of king threadfins usually associated with inshore fishing grounds, especially in the south-east Gulf of Carpentaria, are now being encountered much less frequently, and their movement on and off the grounds is much more erratic than previous years (G. Ward, pers. comm.).

Freshwater allocations to sustain fisheries

The 1994 COAG Water Reform Agreement and various state legislation (e.g. Water Act 2000 in Queensland) requires managers to allocate water to maintain downstream ecosystem health. One aspect of ecosystem health is estuarine and coastal fisheries production. Information on the role of freshwater in maintaining the productivity of commercial and recreational fisheries is needed to ensure that estuaries and their stakeholders are duly represented in the water allocation processes. Natural resource managers (fisheries and water) need to be made aware of the fishing industry’s vulnerability to the impacts of non-fishing activities, such as water regulation. This issue has been identified as a challenge for the fishing industry in reaching sustainable production (see Challenge 1 of FRDC’s R&D Plan 2000, page 59).

Logical frameworks for research leading to new procedures and methods

A logical framework needs to be developed for investigating the role of freshwater flows in estuaries. Procedures to assess the impacts of current and proposed water infrastructure in Australian coastal rivers on estuarine fisheries need to be developed. Methods for monitoring biological responses to environmental flows are needed to provide feedback to managers as to whether desired fisheries-related outcomes are being achieved under current water allocations.

Enhancing the research outcomes - integrating across research disciplines

An integrated research program is needed to develop a robust sampling proceedures that can investigate the role of freshwater flows in estuaries and the impacts of modified flows on fisheries production. The CZCRC offers the opportunity to integrate flow-influenced fisheries data with other hydrological (i.e. costal modelling) and primary productivity (i.e. nutrient cycling) research projects that will provide greater insight into ecosystems processes.