The Varied Uses of Vitality Indicators in Understanding Discard Mortality: Risk Assessment, Mitigation Planning and Fishery-Scale Estimation

There is increasing interest in understanding discard related losses as part of an ecosystem approach to fisheries, a more fulsome accounting of fishing mortality in stock assessments and in promoting the conservation of principally released species. Though these objectives could be achieved by obtaining reliable estimates of discard mortality that are representative of conditions in a given fishery, such estimates are generally costly and technically difficult to obtain and are often not necessary. Reliable proxies of discard mortality susceptibility have been developed based on an individual’s resilience to stressors encountered during capture, handling and release, or based on semi-quantitative assessments of reflex impairment and injury in discarded fish. In this presentation we will demonstrate how these proxies can be used to evaluate the risks posed by discard mortality to species conservation, to prioritize cases for more detailed investigation and to plan management measures aimed at improving the likelihood of successful live release. We will also show the advantages of integrating these proxies into more detailed studies involving captive observations or tagging of discarded fish to obtain flexible and reliable fishery-scale estimates of discard mortality.