A meta-analysis of immediate and delayed discard mortality of red snapper (Lutjanus campechanus)

Red snapper (Lutjanus campechanus) is an economically important fishery in the Gulf of America (formerly the Gulf of Mexico). This species is subject to discard mortality due to barotrauma. Novel discard mortality research on this species has estimated delayed mortality in addition to immediate mortality at the surface (i.e., swim or float). To determine how this combined mortality measurement changes red snapper discard mortality, we conducted a meta-analysis, combining 11 studies, with 92 distinct estimates from 34 years of research. We assessed if depth, season, release method, or region predict discard mortality. We found a significant positive relationship between depth and discard mortality and that, in the western Gulf, fishing in the summer significantly increases discard mortality compared to fishing in other seasons and regions. Analysis of studies with well-defined release method treatments revealed that venting and descending generates a 14.6 % decrease in estimated release mortality compared to no barotrauma mitigation. We estimate a 31 % discard mortality at 33 m, the median fishing depth of the private recreational fleet; this is more than double the discard mortality estimate generated by a previous meta-analysis based on immediate mortality alone. Given that we generated estimates from both immediate mortality and delayed mortality, we propose that these updated, higher estimates of discard mortality are more representative of the mortality experienced by this recreational fishery.