Avoiding bycatch: integrating catch predictions with spatial prioritization in a commercial prawn trawl fishery

Context. Spatial targeting involves relocating fishing effort to reduce unwanted catch (e.g. bycatch) while maintaining target catch. However, it is challenging to measure target-bycatch separation, develop viable scenarios for fishing effort relocation, and measure impacts on fishers. Aims. We demonstrate a simple but data-driven spatial prioritisation analysis, to evaluate whether local changes to fishing location can reduce bycatch with minimal reduction in target catch in an ocean prawn trawl. Methods. Using observed and predicted catch compositions, we extend a published spatial prioritisation method to evaluate the impact of spatial targeting on target catch and bycatch, and measure fisher impact based on the percentage of historical effort relocated. Key results. Spatial targeting's effectiveness varied by species priority. While shark and ray bycatch showed reduction potential (up to a 30-60% decrease in bycatch for a 0-15% decrease in target catch), differences among data sources created uncertainty about priority fishing locations. Limited spatial separation between main target and bycatch species also meant unlikely total bycatch reduction. Fisher impacts varied, with effort redistribution often exceeding bycatch reduction gains. Conclusions. Spatial targeting has the potential for avoiding specific species, but is unlikely to reduce total bycatch in this fishery.