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Bring That Rockfish Down!

barotrauma
“Popped” rockfish that anglers want to or must release should be returned to depth as quickly as possible to increase their chances of survival.

Sea Grant and the California Department of Fish and Game are partners on a new brochure for anglers, explaining how and why to return rockfish to depth quickly. A PDF of the brochure can be downloaded at no cost. You may also request a hardcopy by mail. (Contact: Christina S. Johnson, 858-822-5334, csjohnson@ucsd.edu)

The brochure “Bring That Rockfish Down” gives a basic physiological explanation of why rockfish are prone to pressure-induced injuries. (Every rockfish has a gas-filled organ called a swim bladder that expands and contracts to control its buoyancy. When a fish is caught and reeled in, this mechanism for moving vertically in the water column is thrown out of whack.)

The brochure also discusses the pros and cons of different methods for returning fish to depth quickly and shows pictures of these devices.

USC Sea Grant research led by Cal State Long Beach biology professor Chris Lowe and former Sea Grant Trainee Erica Jarvis, now a marine biologist at the California Department of Fish and Game, documented the viability of returning fish to depth quickly as a means of increasing post-release survivorship in sport-caught rockfish.

Their research, which has been accepted for publication in the Canadian Journal of Fisheries and Aquatic Sciences, shows that for some rockfish species the degree of barotrauma in a fish is not a reliable predictor of whether it will survive being released. Even fish with bulging eyes and protruding stomach can pop back to life when returned to a native depth. Lowe and Jarvis found that the most significant predictor of post-release survivorship is the time a fish spends at the surface.

In experiments with several species of common Southern California rockfish, including vermilion, flag, squarespot and honeycomb rockfish, as well as bocaccio, 83 percent of fish caught at depths between 217 feet and 350 feet, survived when returned to depth within 2 minutes. The odds of a fish dying following recompression nearly doubled with every 10-minute increase in time at the surface.

Tagging and recapture studies showed some released fish were still alive 18 months later.

“We are hoping the brochure will inform and educate anglers about barotrauma and give them some reasons to want to bring fish back down,” Jarvis said. “Anyone who has seen a slick of floaters behind a party boat (rockfish floating on the surface because they are too inflated to re-descend on their own) knows this brochure is needed.”

PDF of Brochure