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Marine Ecology & Stock Assessment Program

Survival of Deep-Water Rockfish After Barotrauma

Because rockfish (Sebastes spp.) are physoclystic (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 and 2011 demonstrated that rougheye rockfish (S. aleutianus) caught at depths from 500 to 800 ft 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 there is potential to conduct scientific tagging studies to track movements and behavior.

In September 2011, we chartered the fishing vessel Seaview, a longline vessel out of Juneau, Alaska, to sample rougheye rockfish on reefs near the NOAA Little Port Walter Research Station on Baranof Island, Southeast Alaska. 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 21 fish that were recompressed immediately after capture in portable pressure tanks, 13 survived and are currently held for long-term monitoring at the ABL Lena Point facility in Juneau.

Some of these fish still have corneal gas bubbles, but other signs of barotrauma have since subsided. Other rougheye rockfish caught during the cruise were tagged and subsequently released at 200-250 ft using a weighted crab ring and a downrigger (n=47). In 2012 we hope to increase the number of tagged fish at-large, make the first attempt to recapture fish tagged in 2011, and increase the number of fish brought back to ABL and held for long-term observation.

By Cara Rodgveller

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