Replenishing rockfish populations

provided by Hubbs-SeaWorld Research Institute

Rockfish, like the bocaccio, canary, yelloweye and cowcod, are vital to the West Coast's marine ecosystem; however, they are among the species that have been severely depleted to meet a growing demand for seafood. Rockfish live so long and reproduce so slowly that it could take nearly a century for the wild population to recover without intervention, even if all fishing were halted. For these reasons, several coastal California rockfish species have recently been petitioned for inclusion on the endangered species list.

    San Diego-based Hubbs-SeaWorld Research Institute (HSWRI) is launching research designed to explore the potential of speeding up the recovery of these rockfish species through stock replenishment. Beginning in March 2003, HSWRI will conduct the research together with the National Oceanic and Atmospheric Administration's (NOAA) National Marine Fisheries Service (NOAA Fisheries), collaborating with NOAA Fisheries' Northwest Fisheries Science Center's Manchester Research Station in Washington.

    “We are beginning a six-month feasibility assessment to see if we can help restore depleted coastal fisheries through stocking,” said Don Kent, president of HSWRI. “Both federal and state agencies have acted to close these fisheries off our coast – a stern measure, but one that was made after significant deliberation and input from stakeholders and with the interests of the wild resource in mind. We are working to develop a program designed to evaluate another management tool for resource agencies,” Kent said.

    Rockfish recovery models predict that replenishment time could be shortened with the release of juvenile rockfish reared in culture facilities and allowed to grow to a size that would promote survival in the wild.

    Kent and his team must overcome some unusual problems with a captive breeding program for rockfish. For one thing, these species dwell deep in the ocean and have internal air bladders, which they use for buoyancy control and to equalize to the massive water pressure experienced on the ocean floor. When the fish are suddenly pulled up to the surface, their bladders expand dramatically, and the fish most often die.

    To capture rockfish breeding stock, HSWRI researchers will go by boat nearly 40 miles off the coast of San Diego and drop lines and traps to a depth of 300 feet. Rather than immediately bringing the fish to the deck, divers will be positioned underwater at 70 feet to intercept the lines, remove the fish and bleed the air out of their bladders with a needle. An underwater pen will hold the fish until they are lifted to the boat.

    HSWRI has constructed cold-water holding pools for the collected broodstock to develop protocols for breeding the adult fish and rearing the resulting larvae and juveniles. “We already conducted a pilot test of this method, and it worked very well,” said Kent. “We have 10 bocaccio rockfish in our holding pools right now.”

    Meanwhile, scientists at the NOAA lab will be using similar methods to establish broodstocks that will be held in net-pens located in Puget Sound. Both labs will then begin the complicated research needed to breed the adults and rear the baby fish.

    When compared to the alternatives of habitat restoration and fisheries closures, marine stock enhancement can be a cost-effective countermeasure to diminishing fisheries populations. HSWRI's research program promises to provide significant insight into preserving important rockfish species through stock enhancement.

    HSWRI is a nonprofit research organization with a 40-year legacy of pioneering scientific discoveries that increase our understanding of animals, their ecosystems, and that provide solutions for the problems that they face. Through science, the application of advanced technologies and the expansion of knowledge, HSWRI works to conserve the natural world, while also ensuring our ability to interact with it. For more information, visit