Evaluating the Efficacy of Descender Devices in Increasing the Survival of Deepwater Groupers Using Telemetry

Discard mortality rates of deepwater (>100 m) groupers (Serranidae; Epinephelinae) have long been assumed to be at or near 100% because these species experience severe barotrauma upon capture.  An effective technique to mitigate barotrauma and increase survival rates of discarded deepwater groupers may help in maintaining or rebuilding populations of these species.  We used acoustic telemetry tags (with acceleration and depth sensors) and submersible receivers to monitor activity of 19 deepwater groupers caught in ~100 m depth and released in the water column after forced recompression using a descender device.  The deepwater groupers were speckled hind (Epinephelus drummondhayi; n=4), snowy grouper (E. niveatus; n=7), and scamp (Mycteroperca phenax; n=8).  Acceleration and depth data were used to assign fates to detected fish.  Of 19 deepwater groupers tagged and recompressed, at least 15 survived beyond 72 h.  For three groupers, there was insufficient data for fate assignment (< 6 h detections) and one grouper died resulting in a proportional discard mortality of ~6%.  Descender devices appear to be a very promising tool for increasing survival of discarded deepwater groupers.