Nearly 3,000 white seabass nursed in covered pens at a Redondo Beach science education and ocean conservation center were smothered to death when a power outage cut their oxygen supply over the weekend.

The fish were grown at SEA Lab as part of the state Department of Fish and Wildlife’s Ocean Resources Enhancement and Hatchery Program, a long-term effort to reestablish strong fisheries for the croakers, whose numbers had thinned to worrisome levels until 20 years ago.

The grow pens at the Redondo Beach SEA Lab produce up to 12,000 white seabass a year in batches of 3,000 to 5,000. Statewide, about 60,000 white seabass are grown to adulthood and placed into the oceans each year as part of this experimental program.

“It’s a shame the 30-some volunteers who clean the tanks, feed and raise the fish will not see their babies released into King Harbor,” said Rich Ford, co-director of the White Seabass Project’s Redondo Beach facility. “The fish were removed from our above-ground tanks and bagged and put in the trash.”

Ford and several volunteers threw out the dead fish after discovering Monday morning that a power outage had shut down the pumps that circulate water and oxygen in the pens.

Southern California Edison spokeswoman Caroline Aoyagi-Stom said the power outage that affected King Harbor began at 3:22 p.m. Sunday when a piece of equipment failed. She did not know the exact cause or nature of the problem, but said most of the nearly 6,000 customers affected had power restored by 9:30 p.m.

Ford said the facility receives batches of young white seabass when they are about 4 inches long from a Carlsbad hatchery. They are fed and cared for at SEA Lab until they mature to 8-10 inches in length. In October, they released 8,998 fish to King Harbor.

The fish that died Sunday had been at the SEA Lab since November and were 8-9 inches long, and set to be released into King Harbor next month, he said. Another shipment from Carlsbad is expected in May. But Ford said he’s disappointed he didn’t get notification of the outage in time to turn on generators that circulate water and oxygen in the fish pens.

“It’s kind of discouraging,” Ford said. “We really do get attached to the fish.

“When we release them, they’re like teenagers leaving home.”