Post Release Survival and Behavior of Deep-Dwelling Rockfishes (genus Sebastes) Suffering from Barotrauma: Using Recompression Devices to Reduce Bycatch Mortality

Rockfishes (genus Sebastes) experience high rates of catch-and-release mortality associated with barotrauma.  As these fishes are brought to the surface, gas in the gas bladder expands with the change in ambient pressure.  This can cause the gas bladder to rupture and leak gas into the visceral and cranial cavities often resulting in bloating, crushed organs, esophageal eversion, exophthalmia (bulging of the eyes), emphysema and emboli in various organs, and excessive buoyancy.  Excessive buoyancy makes it difficult for many species to return to depth under their own power.  Discarded rockfishes are thus often left floating on the surface where they eventually succumb to their injuries or predation.  This study assesses the ability of five rockfish species, including two overfished species (Cowcod, S. levis, and Bocaccio, S. paucispinis, which dictate groundfish management decisions in southern California) to recover from barotrauma if returned to depth using a descending device.  Long-term survival and recovery of these deep-dwelling rockfishes were monitored with accelerometer and pressure sensing acoustic transmitters within an acoustic receiver array on an offshore seamount.  Our results show high rates of survival despite substantial barotrauma-related injury.  These data have already contributed to changes in rockfish bycatch mortality estimates and recreational fishing regulations.