Lahontan fish hatchery off to disease-free year
The chutes and raceways at the Lahontan National Fish Hatchery gurgle as spring approaches and thousands of cutthroat trout bob their heads and jump from the water at anything resembling food.
Some 275,000 hungry fish that occupy the hatchery’s holding tanks have a clean bill of health, which wasn’t the case this time last year.
One year ago this week, nearly 400,000 of the once-endangered Lahontan Cutthroat Trout had to be euthanized after a bacteria called furunculosis was discovered in the fish.
“It’s been slow, but we have recovered and are back on track,” said Hatchery Supervisor Larry Marchant. “These fish will be ready for spring, although we’ve scaled back some.”
Because of last year’s loss, the hatchery reduced the number of fish it raises. In a normal year, 650,000 fish are raised in the hatchery. This year, about 500,000 fish are being raised.
After last year’s loss, which cost the hatchery about $200,000, officials were forced to take stronger measures to ensure the fish they raise are healthy and bacteria-free.
Furunculosis is caused by naturally-occurring bacteria in wild waterways in Northern Nevada. It affects the internal organs of the fish, shutting down the kidneys and causing sores on the fish’s scales. In a closed environment like a fish hatchery, the young fish are more vulnerable than they would be in a fast-moving stream or open lake, Marchant said.
Questions remain about the origin of the bacteria.
Fishery biologists believe the bacteria entered the hatchery through one of two sources -underground well pipes that may have been damaged in the 1997 New Year’s Flood or wild birds that come to the hatchery in search of food.
While it is difficult to determine which was the cause, hatchery officials have tried to alleviate some of the problems.
The damaged well lines have been replaced, and fish netting has been hung on chain link fences to keep the birds out. Carriers of the bacteria are great blue herons, belted kingfishers and American dippers.
Also, the hatchery has beefed up its disinfectant protocol. Using sodium hypochlorite, the hatchery holds the chemical in its pipelines and waterways for up two hours to ensure bacteria is killed. Before, standard protocol was a flush of the system.
“While there’s no guarantee that it won’t return, we’ve done a lot,and have taken precautions to make it more difficult for it to appear,” Marchant said.
Even when the hatchery took precautions after traces of the bacteria were found, it lost more fish after the first series of euthanizations in 2000.
After the first batch of infected fish were euthanized, only fresh water was cycled through 21 of 36 raceways in the facility, which recycles a small portion of the water. Officials hoped this precaution would be safer for the remaining cutthroat, because recycling the water put the fish at risk again.
Antibiotic treatment was continued, but in mid-March of 2000, another outbreak was detected in five of the 21 operating raceways and 61,000 more fish had to be euthanized. Of the remaining cutthroat fingerlings, 135,000 were released into Walker Lake last spring.
This year, the hatchery released half of its population – about 225,0000 of the healthy fish into Pyramid Lake. In spring, about 75,000 will be dumped into Walker Lake and about 35,000-40,000 into the Truckee River.
The Lahontan Cutthroat Trout is listed as a threatened species under the Endangered Species Act. Around 650,000 are raised annually at the fish hatchery, for release primarily in Pyramid and Walker lakes and the Truckee River.
Eggs are obtained from March through June from spawning wild fish living in Pyramid Lake. The following year, the lake is stocked with 7-inch hatchery fish. The fish can grow up to 15 pounds and are popular with sport fishermen.