Video: Whirling disease infects trout in area fish hatcheries
The tanks in one secluded area at the Mount Shasta Fish Hatchery teem with nearly 1,000 immensely precious trout.
These are redbands, a rare relative of rainbow trout. Biologists with the California Department of Fish and Wildlife rescued them late last summer from three nearby creeks that had become little more than a trickle after years of drought.
In the same hatchery, nearby holding ponds brim with wriggling masses of more common trout species. These are rainbow and brown trout that aren’t rare or threatened, but are central to a massive statewide production mill in which millions of trout are bred, reared, then released into nearby waterways to be caught by recreational anglers.
The browns and rainbows at the Mount Shasta hatchery are under isolation for a very different reason from their redband cousins.
State fisheries officials worry they may be carrying the spores of a highly contagious parasite that causes an ailment called whirling disease, which can decimate trout, salmon and steelhead populations. The parasite has been found in various state waterways for decades, and hatchery officials are trying to stop it from spreading further through infected hatchery trout.
They have quarantined Mount Shasta and another north state hatchery, Darrah Springs, where the new outbreak is believed to have originated. All told, the 3 million trout under quarantine equal about 15 percent of the trout stocks at state hatcheries.
Those imperiled redband trout at the Mount Shasta hatchery should be safe from the disease, despite their proximity, officials said. They’re being kept in an area that draws on a contained, parasite-free water system.
But as California weathers a fourth year of drought, the scenario playing out at the oldest trout hatchery west of the Mississippi River could portend a more complicated future for the state’s fish-hatchery system. As streams holding rare native fish dry up, it will put more pressure on the Department of Fish and Wildlife to choose between two distinct and sometimes competing mandates: sheltering endangered species to prevent their extinction, while simultaneously producing ample fish stocks for recreational anglers.
With limited hatchery space, that could mean even fewer fish for anglers to catch in the summers to come.
“If we go into Year 5, there’s going to be a bunch of very serious decisions that will have to be made,” said Harry Morse, a department spokesman.
California’s hatchery system dates to the Gold Rush, when strip mining tore up river banks and related pollutants severely damaged fish habitat.
The 22 hatcheries in the system historically served separate but married purposes. Typically, the system of nine hatcheries that breed salmon and steelhead get the most attention. These facilities, including the Nimbus Fish Hatchery below Folsom Lake, were designed to keep runs of migratory salmon and steelhead viable despite the network of dams that block off native spawning grounds.
The system also includes 13 hatcheries dedicated to populating rivers and lakes with recreational trout. Mount Shasta, which opened in 1888, is the oldest of these.
Over the decades, California’s trout hatcheries have played a growing role in bolstering the state’s recreational fishing culture. The Department of Fish and Wildlife is bound by state law to stock ample fish in the state’s rivers and lakes to keep recreational anglers happy. These anglers’ license fees help fund the hatchery system and the department as a whole. Last year, the state sold 1.78 million fishing licenses.
Trout are among the most popular fish to catch in California, and tanker trucks, typically filled with half-pound rainbows, remain a common sight coming and going from reservoirs. For decades, the agency also has used airplanes and even pack mules to dump hatchery-bred trout into high mountain lakes and streams where tanker trucks can’t go.
Trout stocking days are celebrated by many anglers, because they can mean easily attained bag limits of the naive hatchery fish that gobble down bait more aggressively than wilier native fish. The state posts detailed stocking schedules online, and many newspapers publish them.
But, much as the drought has affected spawning streams, it also is taking a toll on the state’s trout-stocking program. In 2008, the agency stocked 4.3 million pounds of trout. This year, it’s down to 1.6 million pounds – and the fish being planted are smaller than normal.
Fearing that low water levels and oppressive heat would lead to catastrophic losses of some trout, hatchery officials stocked many lakes and streams earlier than normal this year, while waterways were still cool. That means the fish had less time to mature. Instead of half-pounders, many of the fish released this year were half that size.
Jim Reid, the owner of Ken’s Sporting Goods in Mono County, said anglers are noticing. He said one group recently told him that they had caught only a dozen fish in a lake where typically they would land 50 or 60 a day.
“This year,” Reid said, “it’s definitely been a lot less, and a lot smaller fish.”
Bill Cox, hatchery system manager at the Department of Fish and Wildlife, said the whirling-disease quarantine is putting further strain on the stocking system. But it’s necessary, he said, to ensure the safety of the steelhead and salmon populations.
“Although we don’t think that this disease would have an affect on those populations,” Cox said, “we’re being very cautious about it.”
The infection itself may be a result of the drought. Cox said the working hypothesis is that a bird such as a great blue heron or some other predator ate a fish from Battle Creek, a stream near the Darrah Springs hatchery that has hosted the parasite for at least three decades.
With so little water in the area, the thinking goes, the predator found its way to the spring that feeds some Darrah hatchery holding ponds. It defecated in the water and spread the spores to aquatic worms. The worms spread the spores to the fish.
Not knowing the spores were in the fish, hatchery officials shipped some from Darrah 90 miles north to Mount Shasta.
Whirling disease destroys cartilage in young fish to the point where they lose spinal control and equilibrium, the behavior that gave rise to its name. The disease has devastated trout populations in Montana and Colorado, but so far has had little impact on California’s native fish populations.
Fisheries biologists say the detection of whirling disease doesn’t necessarily mean a death sentence for every fish at a hatchery.
Cox said biologists are sampling fish from various holding ponds at the two hatcheries and killing groups of fish that test positive. The hope is that the infection is contained to only a few holding ponds, which will be treated before new fish are brought in.
But that’s not going to help trout anglers this summer: Their fishing lines, Cox said, might stay limp longer.
“Things might not be the same as they always are,” he said, “because this drought has impacted everything we deal with.”
Ryan Sabalow: (916) 321-1264, @ryansabalow.