Integrated approach to improving stock assessment of Black Jewfish
Charles Darwin University (CDU)
David A. Crook
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.
1. Quantitative models of relationships between external and physiological drivers and their effects on productivity and recruitment in Black jewfish populations
2. Evaluation of the performance of high-resolution sonar surveys for obtaining fishery-independent data on population abundance and size-structure
3. Improved stock assessment for Black jewfish via integration of study's outputs, leading to increased stakeholder confidence in the information used to support management