NIPOMO MAN RAISES RAINBOW TROUT

Fishing for a solution to trout disease

Gene Carl raises fish resistant to a disease ravaging trout populations to help stabilize their numbers

By David Sneed

Gene Carl flings a handful of brown pellets, and the surface of a fish raceway boils for a moment as dozens of trout hungrily snap up the food.

The fish are 4-month-old fingerling rainbow trout. But they aren’t ordinary rainbows. Instead, they are a special strain from Germany that is resistant to a deadly disease ravaging trout populations throughout much of the world.

At the beginning of the year, the state Department of Fish and Game gave Carl 30,000 Hofer trout eggs for hatching and initial rearing at his hatchery in Nipomo. Hofer trout are resistant to whirling disease, a parasite that deforms trout fingerlings and fry, causing them to swim in circles.

“We had an excellent hatch,” Carl said.

The trout will be transferred to another hatchery in Mono County, where they will likely be released along the eastern slope of the Sierra Nevada to drive down whirling disease infection levels there. He has already shipped 1,100 pounds of Hofer trout and has about 5,000 pounds more.

Carl’s hatchery was selected because it is new and one of the few in the state that is not infected with the disease, said Bill Cox, supervising biologist who manages the state’s hatchery program.

“Hofer trout are new fish for the state,” he said. “We are not exactly sure how we are going to utilize them.”

Whirling disease was first discovered in Germany a century ago. It has a 90 percent mortality rate. Swimming in circles prevents the fish from feeding and makes them vulnerable to predators, Cox said.

The disease has been in California since 1965. Hofer trout evolved with the disease in Germany and are more resistant to it. The Hofer trout are the newest tool being used to keep the disease under control.

Getting the Hofer trout eggs from the state was a big step for Carl, who has been raising trout at his Lone Pine Nursery on North Thompson Avenue as an elaborate hobby for the past four years. He now has six raceways — long, water-filled concrete troughs in which the trout live. He also raises catfish in a pond at the nursery.

Since he started the hatcher y, Carl has been experimenting with new rearing techniques tailored for the conditions of the Nipomo Mesa. Unlike most hatcheries, he uses pumps to recirculate and aerate the water in the raceways, reducing the amount of water typically used by a hatchery by 85 percent.

He keeps the water warmer than typical, which allows the fish to grow faster. He also has found that the water used in the hatchery is excellent for irrigating the eight acres of plants in his nursery. He says the fish help pull some of the salt from his well water and make it more balanced.

Carl’s success with the Hofer trout has caught the attention of other groups and agencies. He hopes biology students at Cal Poly will want to use his hatchery for some of the college’s trademark “learn by doing” work.

San Luis Obispo is likely to use Carl’s facility this winter to hatch some artificially spawned trout eggs from Whale Rock Reservoir near Cayucos. The city uses it as one of its water supplies and occasionally artificially spawns trout from the lake to sustain the population, said Freddy Otte, a city biologist who is a fisheries biologist by training.

“Gene’s got the ability to raise a lot of fish,” Otte said. “I’m very jealous.”

With lots of refinements and observations under his belt, Carl feels he is ready to branch off into other fish. He plans to raise salmon as his next challenge.

“These are very touchy fish,” he said, referring to the rainbow trout. “If I can make trout work, I can make anything work.”