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Something in the Way Bocaccios Move

By Julie Zeidner Russo

The prized bocaccio, a large, edible rockfish of American Pacific waters, which gets its name from an Italian word meaning ugly mouth, is now sending a message to researchers at the Moss Landing Marine Laboratories.

Rockfish have been caught since the late 1800s. Today, they are one of the most popular commercial and recreational fish on the West coast. They also fascinate fisheries biologists because of their diversity and longevity--there are 57 species of rockfish in Pacific waters alone, and some can live to be more than 100 years old. "Fishing effort for rockfishes and landings have increased dramatically over the last forty years," said marine biologist Richard Starr of the California Sea Grant Program. "Historically rockfish landings have been high especially in Monterey Bay area, but there are now indications that numbers and size composition are decreasing for some species." The bocaccio population is less than 20 percent of what it was in 1970, according to the National Marine Fisheries Service, and the World Conservation Union considers bocaccio at high risk of extinction.

At one time, rockfish were hard to get to by line or net. Their preferred habitat of deepwater rocky outcroppings and pinnacles made them less prone to exploitation, and they could flourish within Monterey Bay's natural harvest refugia. But as local stocks of rockfish have become depleted, the Monterey fleet is going greater distances and depths to find them. Fisheries managers are now in a race to establish marine fisheries reserves and parks to protect rockfish. "A number of reserves, which serve as undisturbed areas of research or protection where fishing is prohibited, exist in California," said John Heine, a research biologist with the Moss Landing Marine Laboratories, "but their effectiveness in fisheries management is largely untested."

Finding out how bocaccios move is a critical piece of information in establishing marine reserves to protect them. With support from the National Undersea Research Program, a novel technique of tagging rockfish underwater and observing their movements is underway by researchers Starr and Heine, Moss Landing marine biologist Gregor Cailliet, and California Sea Grant research technician Jason Felton. The project has already yielded some interesting results that could be used by researchers and managers in the study and management of rockfish as well as other fisheries.

Traditionally, fish have been tagged with visual external ID tags or at shallow depths where they are brought to the surface, tagged with an external marker, and released, the scientists said. "Researchers then wait for tag recoveries to return via the commercial or recreational fishery," Heine said. "Such studies provide long-term movement data, but little information about short-term movements." However, few researchers have successfully tagged deepwater species. Since bocaccio live at depths of up to 300 m or more bringing them to the surface without bursting their swim bladders would be difficult. Methods of tagging deepwater fish have also met with poor results since fish enticed to swallow sonic tags tend to regurgitate them and surgical methods of attaching the tags externally may traumatize the fish and affect their behavior.

Last summer, scientists performed a new six-minute procedure they developed and tested at the Monterey Bay Aquarium to surgically insert an acoustic transmitter inside rockfish. A commercial fisherman assisted in bringing the rockfish up to a 20 m depth using longline gear, then SCUBA divers descended to the depth of the captured fish, anesthetized them one at a time, and surgically implanted the acoustic transmitters in the bocaccio.

Sixteen bocaccios--each outfitted with its own unique frequency tag--released on the bottom at the location of the catch sent radio signals back to researchers showing their individual locations. Several weeks after the fish were tagged, the scientists used the Delta submersible to place six recording receivers on the sea floor to assist in the tracking of vertical and horizontal movements of the fish. This would be the first time researchers had developed techniques to obtain semi-continuous information about fish movement during a three month period, Heine said.

Schools of up to 100 rockfish at 150 m depth--and amazingly, three of the tagged bocaccio located by the hydrophone-- were observed by the scientists during their underwater excursion. What the researchers discovered was that the rockfish tended to move up the rock walls during the day and move down at night in a range of about 10 to 20 m, Felton said. Occasionally, the bocaccio dove much deeper in dives that exceed 200 m for unknown reasons, he said. Their horizontal movement was more illusive since they may have hidden under rock ledges or inside canyons. The bocaccios' range--as much as several kilometers in either direction-- also surprised scientists who thought their horizontal movements would be smaller. "Results of this work should provide important information related to home range and frequency of emigrations from harvest refugia," Starr said. The researchers are already applying the techniques used for studying the movement of bocaccio to other species like the prickly shark, with the hope that it improves the design of future marine reserves.

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