Release mortality in the red snapper (Lutjanus campechanus) fishery: A meta-analysis of 3 decades of research

Abstract

The value of catch-and-release fishing as a conservation measure is highly dependent upon rates of discard frequency and release mortality. Therefore, it is important to understand how estimates of these variables are affected by factors such as capture depth and water temperature. The meta-analytical approach to modeling used here for red snapper (Lutjanus campechanus) in the Gulf of Mexico provides a robust method for dealing with studyspecific differences in experimental protocols and for estimating release (discard) mortality as a function of key factors. Results of this analysis showed significant increases in mortality by depth and for the commercial sector. The most consistent result was the positive correlation between depth and estimates of release mortality, a relationship that was present regardless of study method, fishing sector, hook type used, or season of study. The effect of venting (deflating the swim bladder by puncture) was dependent on whether the study produced estimates of immediate or delayed mortality. Immediate estimates indicated that mortality rates are lowered by venting whereas delayed estimates indicated that venting increased mortality rates. This result is largely reflective of the use of submergence ability, from surface-release studies, as a proxy for mortality. The model’s interaction result indicates that recompression of fish may be a viable alternative to venting and that, if a recompression device is not available, venting at least improves the likelihood that a fish can submerge and return to protective habitat. The depth-based functional relationships developed in this model were used in the most recent red snapper stock assessment in 2012, and that use was a change from previous assessments where region-specific point estimates were used.