AFSC/ABL: Rockfish Barotrauma

Because rockfish (Sebastes spp.) are physoclystic, i.e. their gas bladders are closed off from the gut, they often suffer internal injuries from rapid, internal air expansion when caught and brought to the surface. Many discarded rockfish do not survive either because they cannot submerge due to excessive buoyancy or because of internal damage. There is some evidence that recompression may greatly increase the survival of barotrauma-injured rockfish. However, because survival can be species-specific it is important to gauge the impacts on each species of interest. Research completed in 2010 on a small NOAA vessel demonstrated that rougheye rockfish (S. aleutianus), caught at depths down to 700 feet and exhibiting barotrauma, can survive if recompressed after capture in portable pressurized tanks. This result is noteworthy because it is the deepest known successful capture and recompression of any rockfish species, which suggests theres potential to conduct scientific tagging studies to track movements and behavior. In 2011 and 2012 we chartered a longline vessel to sample rougheye rockfish on reefs nearby the NOAA, the Auke Bay Laboratories (ABL), Little Port Walter Research Station on the southeast side of Baranof Island. After rougheye were caught and brought to the surface, they exhibited signs of barotrauma such as stomach eversion, exophthalmia (bulging eyes), and corneal gas bubbles. Of 43 fish that were recompressed immediately after capture in portable pressure tanks, 25 survived and are currently held at TSMRI for long term monitoring. The deepest fish that was captured and has survived long-term was caught at ~915 feet. Some fish still have corneal gas bubbles, but other signs of barotrauma have since subsided. Other rougheye rockfish were tagged and released at 250 ft using a weighted crab ring and a downrigger (n=130).