Design and implementation of a tropical snapper trawl survey

Tropical snapper are important target and by product species of several northern fisheries including the Northern Territory’s Demersal Fisheries, the Timor Reef Fishery and the Queensland Gulf of Carpentaria Developmental Fin Fish Trawl Fishery (GOCDFFTF). Stock assessment of these fisheries relies on stochastic stock reduction analysis models which rely on a long-term catch and effort history, a time-series index of abundance – such as catch per unit effort (CPUE) or fishery independent survey data – length data, age data and biological and population parameters. With no recent fishery-independent index of abundance, assessments rely on CPUE from commercial catch and effort data. The use of commercial CPUE as an indicator of relative abundance can be problematic for many reasons, compromising the underlying assumption that commercial catch rates change linearly with abundance. This project worked closely with the Northern Territory Government and the fishing industry to design a cost-effective and statistically robust fishery independent survey. This survey is currently being undertaken.