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Identifying population connectivity of shark bycatch species in NT waters
This project is needed for three main reasons:
1. It directly addresses a NT RAC priority in the 2019 call for funding applications relating to improving sustainable yield estimates to inform stock assessment programs for undefined target species and protected species in the Offshore Net and Line Fishery. The project will support sustainable fishing practices for important commercial fisheries in the NT and the development of new commercial opportunities within these fisheries: The impacts of fishery activities on these species, either through bycatch or targeted harvest, are difficult to assess in the absence of information on population connectivity and stock structure.
2. The project will develop capacity for fisheries research and monitoring in NT waters. Genetics methods are widely applied to fisheries research and monitoring and training of an early career fisheries scientist in the application and interpretation of genetic data will be a key outcome of this project.
3. The project will provide key information to support the transition of these species from bycatch to a harvested byproduct species, including an evaluation of leading-edge genetic techniques in fisheries assessment and monitoring.
Integrated approach to improving stock assessment of Black Jewfish
Current stock assessment of Black jewfish in the NT relies on outputs from a Stock Reduction Analysis (SRA) based on assumed stock-recruitment relationships and catch-and-effort information. Increases in Black jewfish catches in 2017/18 after several poor years were inconsistent with the SRA forecasts, demonstrating a need: 1) to better understand the drivers of fishery productivity and recruitment; and 2) for information on abundance and size-structure.
Environmental variability strongly influences abundance and recruitment in coastal fisheries of northern Australia. In contrast to Barramundi and King threadfin, anecdotal information suggests that Black jewfish catches may be negatively correlated with freshwater outflow during the wet season. However, data on external drivers of population structure and physiological responses to environmental variability are currently lacking.
Another critical knowledge gap is the abundance and size-structure of Black jewfish populations. At present, the only information available is from commercial catch data and surveys of recreational fishers. These fishery-dependent sources have important biases, particularly size selectivity. There is an urgent need for more robust, fishery-independent data on population abundance and size-structure for Black jewfish.
This project will examine a range of environmental variables and physiological parameters from sampled fish to identify the key drivers of productivity and recruitment for Black jewfish. We will also collect fishery-independent data on the abundance and size-structure of Black jewfish populations using high-resolution sonar, with a view to developing a monitoring methodology to support the CLF harvest strategy.
The overall goal is to improve the accuracy and predictive performance of Black jewfish stock assessment, thereby increasing confidence in the information used to justify management decisions and providing increased certainty to fishers across all sectors. A new, full-time post-doctoral fellow position, jointly funded by CDU and AIMS, will lead the project activities under the supervision of the project investigators. FRDC funds are requested for technical assistance, travel and operating.