Posted by on May 17, 2005 at 08:29:43:
More than 6,000 juvenile white seabass were released in San Diego Bay April 30 as part of an ongoing effort to re-establish the fishery. White seabass were once common along the California coastline. Due primarily to overfishing, their population declined several decades ago. Since then, strict size and bag limits combined with hatchery programs have helped the population rebound.
“We released 6,103,” said San Diego Oceans Foundation Executive Director Noelle Morris. “We counted so many that my head was spinning.”
These white seabass were sired from brood stock kept at the Hubbs-SeaWorld Research Institute’s Hubbard hatchery in Carlsbad, Morris said. When the seabass reach 3 inches, they are shipped from the Agua Hedionda Lagoon facility to 15 grow-out pens throughout Southern California.
The young seabass arrive in a specially designed stainless steel trailer. At most grow-out facilities, the trailer is positioned near the pen, and the fingerlings are netted and carried in buckets to the pens. But since the facility in San Diego is adjacent to a rather tall pier, juveniles are treated to a special ride.
“They’re placed into a fish delivery pipe,” Morris said. “It’s a big PVC pipe we installed at the base of the pier. When the fish arrive in the truck, we hook up the truck and pump seawater from the bay into the pipe. The fish flow down the pipe into the pen, just like a water slide.”
The fish are fed once an hour, 24 hours a day until they are ready to be released in about four months. “They’re fed tiny pellets of fish food through an automatic feeder. We also have volunteers come and hand feed them every day so the fish don’t become reliant on the automatic feeder.”
The fish are released when they reach 12 inches. The release process begins when volunteers crowd the fish near the surface by lifting up the bottom of the pen. Then, the fish are gently lifted with hand-held nets and counted before being carefully released and allowed to swim away.
The foundation does not plan a release around tidal movements. Nevertheless, the fish make it to the open ocean. “We’ve done some tests with electronic tags and found that virtually all of the tagged fish eventually leave the bay,” Morris said.
While it is impossible to determine the fate of the fish after they reach the open ocean, worries by some that releases spawn feeding frenzies by seals and other predators are unfounded. “We’ve never had a seal problem in San Diego Bay,” Morris said. “We’ve had a couple of seals attack the pens in Mission Bay, but if you keep the nets repaired, the seals lose interest.”
After releasing a batch of fish, San Diego Oceans Foundation workers allow the facility to remain empty for a few weeks. Volunteer scuba divers then clean the pens.
The San Diego Bay grow-out facility has the ability to rear about 80,000 juveniles per year, but has never reached that capacity. “We get a batch every four months on average,” Morris said. “It depends on the weather. The fish grow more quickly in the summer.”