Venting and Rapid Recompression Increase Survival and Improve Recovery for Red Snapper with Barotrauma

Red Snapper, Lutjanus campechanus, are the most economically important reef fish in the Gulf of Mexico. Population assessments that began in the mid-1980?s found red snapper to be severely overfished and lead to extensive regulations and harvest restrictions. As a result of these regulations many fish that are captured must be released and are known as regulatory discards. Red snapper live deep in the water column and when captured and rapidly brought to the surface they often suffer pressure-related injuries collectively known as barotrauma. These injuries include a distended abdomen and stomach eversion from the buccal cavity. High mortality of discards due to barotrauma injuries impedes recovery of the fishery. The purpose of this study was to evaluate the efficacy of two techniques designed to minimize barotrauma-related mortality: venting and rapid recompression. In laboratory experiments using hyperbaric chambers, I assessed sublethal effects of barotrauma and subsequent survival rates of red snapper after single and multiple simulated capture events from pressures corresponding to 30 and 60 m. I evaluated the use of rapid recompression and venting to increase survival and improve recovery indices, including the ability to evade a simulated predator. A condition index of impairment, the barotrauma reflex (BtR) score, was used to assess sublethal external barotrauma injuries, reflex responses, and behavioral responses. Greater capture depths resulted in higher BtR scores (more impairment). Non-vented fish had higher BtR scores than vented fish after both single and multiple decompression events. All fish in vented treatments from 30 and 60 m depths had 100% survival after a single capture event. Non-vented fish had 67% survival after decompression from 30 m and 17% survival from 60 m. Behaviorally, non-vented fish showed greater difficulty achieving an upright orientation upon release and less ability to evade a simulated predator than vented fish. Rapid recompression also greatly improved survival compared to surface-released fish with 96% of all rapidly recompressed fish surviving. These results clearly show that venting or rapid recompression can be effective tools for alleviating barotrauma symptoms, improving predator evasion after a catch-and-release event, and increasing survival. Fisheries managers should encourage the use of either of these two techniques to aid in the recovery of this important fishery.