Workers disinfect fish hatchery
“And stay out!” you could almost hear workers at the Lahontan National Fish Hatchery say to a stubborn bacteria as they painstakingly disinfected the raceways and intakes at the Gardnerville facility that has seen more than its share of disaster since late last fall.
Hatchery supervisor Larry Marchant, clad in bright yellow protective gear with a respirator temporarily pulled off his face so he could talk, said disinfecting the hatchery is normally done in June or July, but was bumped up a few months in an effort to completely eliminate the bacteria, furunculosis, that has been responsible for the loss of more than 500,000 Lahontan cutthroat trout since November.
“We’re taking extra precautions because of the bacteria,” Marchant said Monday afternoon. “Normally we would use 16 barrels of of 13 percent sodium hypochlorite and shoot for 200 parts per million in the raceways, but today we’re using 20 barrels and have around 250 to 300 parts per million in there so far. We want it especially hot to take care of the bacteria.”
– Where is it coming from? Furunculosis is caused by bacteria occurring naturally in the wild waterways in Northern Nevada. It affects the internal organs of the fish, shutting down the kidneys. In its worst expression, sores erupt on the skin, Marchant said.
In the closed environment of a fish hatchery, the young fish are more vulnerable than they would be in a fast moving stream or open lake, according to Randi Thompson, spokeswoman for the U.S. Fish and Wildlife Service.
“In the wild, the bacteria might bounce on them and get washed away,” she said. “But in a hatchery, they’re more crowded and vulnerable.”
Marchant said fisheries biologists believe the bacteria entered the hatchery through one of two sources – underground well pipes that many have been damaged in the 1997 New Year’s flood or wild birds that come to the hatchery in search of free fish.
Chain link fence walls, erected to keep the birds out, have only eliminated the larger species, such as Great Blue Herons, Marchant said, but smaller birds including Belted Kingfishers and American Dippers, can still get in.
“We’re still trying to isolate the source,” he said. “We had a team of fish health people here Thursday, and they’ll be back to help figure out how to pressure test the pipes. That is going to be key. We are using sentinel fish at the water outlet, and if they get sick, we’ll know that the furunculosis came from the broken pipes.”
After the first batch of infected fish was humanely euthanized in early February, Marchant said only fresh water was cycled through 21 of 36 raceways in the facility which generally recycles a small portion of water. This precaution was hoped to be safer for the remaining 200,000 young cutthroat, since recycling the water means potentially reintroducing the bacteria.
Antibiotic treatment was continued, but in mid-March, another outbreak was detected in five of the 21 operating raceways and 61,000 fish had to be euthanized, Marchant said.
Of the remaining cutthroat fingerlings, 135,000 were recently released to Walker Lake. The rainbow trout – around 4,500 of them – grown for the annual children’s fishing derby held in June are fine and being held in fresh water tanks, Marchant said, as are the around 80 brood stock for what is believed to be genetically pure Lahontans from Pilot Peak and more than 25,000 of their offspring fingerlings.
– Working together for the fish. The Gardnerville hatchery will not release fish to Pyramid Lake this year as a precaution to fish there, but the Pyramid Paiute tribe, who operate the lake’s hatchery, have stepped up and volunteered to release 50,000 fingerlings to the Truckee River, Marchant said.
“We are in a 5-year agreement with the tribe and the Nevada Division of Wildlife to evaluate the trout in the Truckee River,” Marchant said. “If the tribe hadn’t stepped up to help, we might have had to extend the study or make up for it next year.”
Marchant said the Truckee River study has involved stocking fin-clipped identifiable fish at specific sites from the Wadsworth bridge to the state line. Data collected from this study will be used to evaluate cutthroat movement in the stream.
– Threatened species. The Lahontan cutthroat trout is listed as a threatened species under the Endangered Species Act. Hundreds of thousands are raised at the Lahontan National Fish Hatchery – usually around 650,000 per year – for release primarily in Pyramid Lake, Walker Lake and Truckee River.
Next month, hatchery biologists will begin the annual collection of eggs for next year’s hatchery crop. Ordinarily taking around one million eggs, Marchant said they will cut back by about 25 percent this year to exercise caution in case the worst-case scenario involves furunculosis at the hatchery again next year.
Marchant said after the disinfection is completed, the raceways will remain dry until mid-summer, when young fry will be large enough to go out there. If there is any further indication of furunculosis, several techniques can be used, including ultraviolet light, sentinel fish at the water intakes and vaccines.
Fisheries biologists will want to eventually convert the Carson Valley hatchery to a fresh water, non-reuse facility, especially after this year’s events. Three additional wells will be needed, bringing the total on the site to seven wells. One well can cost up to $750,000, Marchant said.
During the disinfecting process, the hatchery was closed to the public because of the potentially dangerous fumes created by the chemicals, but opened Tuesday, he said.