Assessing the Relative Vulnerability of Chondrichthyan Species as Bycatch Using Spatially Reported Catch Data Series

Fishery impacts pose threats not only to target species, but also to bycatch species. Nevertheless, choosing priorities for conservation or research in fisheries is often driven by economic value and most retained bycatch species such as sharks and rays have been historically of low profit. Traditional stock assessments usually require large quantities of data, financial support, and feasible study conditions. The multi-species nature of Chondrichthyan catch along with their relatively lower value and sparsity of fishery-independent data creates significant challenges to developing accurate impact predictions. This study introduces a novel technique to quantify the relative vulnerability of Chondrichthyan species taken as bycatch. The approach is based on spatial interactions between species and fishing activity (termed here the fishery interaction index, or FII) and is correlated to metrics of productivity. A database of 15 years of fisheries logbooks was used to apply the method to 20 bycatch sharks and target species in one of the largest fishing sectors of Australia’s EEZ. Overall vulnerability based on the FII-productivity combinations obtained was found to agree considerably with the IUCN status of the assessed species, with only a few exceptions that reflected the local status differing from the general global assessments.