What’s Become of the Discarded? Methods and Trade-Offs for Estimating (and Reducing) Release Mortality

Due to high commercial and recreational discard rates, post-release mortality (PRM) estimates are direly important to fisheries management and conservation. Among other functions, PRM estimates are utilized in stock assessments, setting allowable catch limits, and establishing accountability measures for a fishery. Studies estimating PRM can also indirectly help derive best capture and handling practices that reduce mortality. As such, PRM research effort has increased substantially in recent years. Multiple direct (e.g., various telemetric strategies, holding pens and captive trials) and indirect (e.g., RAMP and vitality/condition indexing, physiological tools) methods have been used to estimate PRM; however, trade-offs involving logistics, cost, PRM underestimation or overestimation biases, and allowable post-release windows, exist for each strategy. Thus, careful deliberation regarding factors like species and gear-type is necessary before settling on the best approach and analytical strategy for a particular study. Moreover, due to the vast range in fisheries practices, and physical and biological factors that influence PRM, recent work has combined direct and indirect study methods to enable broader scaling and applicability of PRM data at the fisheries level. This talk will review trade-offs, synthesize lessons from past studies, and highlight future directions for methods that promote the most accurate PRM estimates.