Depth and water temperature drive elevated post-release mortality of gray triggerfish (Balistes capriscus)

Post-release mortality of regulatory discards is a persistent challenge in marine fisheries management, with inaccurate estimates risking biased stock assessments and ineffective regulations. We used data from a multi-year, large-scale mark–recapture program to estimate post-release mortality of gray triggerfish ( Balistes capriscus ), a highly targeted reef-associated fish in Florida’s coastal and offshore waters. We developed a discrete-time relative-risk model that posited post-release survival as a nonlinear function of depth and sea surface temperature (SST), while accounting for spatiotemporal variation in fishing effort and uncertain reporting rates. Our best-fitting model suggested post-release mortality increases with both depth and SST, enabling temporally explicit, observation-based predictions. Our estimates of post-release mortality are consistent with recent studies reporting high post-release mortality for this species. Moreover, our results align with recent evidence that post-release mortality has been increasing over time as anglers fish in deeper waters farther offshore. The strong temperature effect is also consistent with recent findings of heightened thermal sensitivity in gray triggerfish compared to other highly targeted reef fishes. Together, these results highlight key environmental drivers of post-release mortality and provide an approach for improving stock assessments and management strategies for this and other ecologically and economically important fishery species.