Fish hatchery shows signs of disease
The Colorado Division of Wildlife is scrambling to investigate how water that carried the parasite that causes whirling disease infiltrated its trout hatchery in Carbondale and whether there is an ongoing threat to the fish.
The wildlife division suspects that springs that supply water to the Crystal River Hatchery became tainted when irrigation water from a ditch leading from the Crystal River overflowed.
It’s unknown at this point whether the problem can be solved merely by blocking the ditch water or if the spring now carries the parasites, according to Rich Kolecki, the DOW’s chief of hatcheries.
Tests are under way with “sentinel fish” to see if the potential for whirling disease still affects the hatchery, he said. Trapped fish that are known to be free of whirling disease will be placed in various water sources at the hatchery. Those sentinels will be tested every 10 to 20 days for the disease.
One fish tests positive
The wildlife division said in a press release issued Friday that only the parasite that can cause whirling disease had been discovered at the hatchery. But Kolecki confirmed that one rainbow trout of the Bel-aire strain tested positive for the disease.
He said 20 fish were tested, and one tested positive. The group of about 17,000 fish located where the infection was found was isolated.
Whirling disease attacks the nervous system of some trout species. It can cause skeletal and cranial deformities that make the fish swim in circles and, ultimately, kill them. It affects only younger fish, often killing them before their second year.
Whirling disease has devastated the reproduction capabilities of wild rainbow and brook trout in some rivers and streams in Colorado and other western states.
The Colorado Division of Wildlife has battled over the last decade to keep the disease out of its hatcheries and disinfect the ones that have been invaded. Currently there are three hatcheries operated with the understanding that whirling disease will never be eliminated and two others that are being restored, according to division spokesman Todd Malmsbury.
Hatchery’s unique role
Kolecki said the disease poses a limited threat to the Crystal River Hatchery because the Carbondale facility is primarily a brooding station. It produces 12 million fish eggs annually that are delivered to other hatcheries throughout the state. Those trout are eventually stocked in lakes and streams.
Aquatic biologists with the wildlife division don’t believe that whirling disease can be transmitted from fish to egg. Therefore, the eggs produced in Carbondale can continue to be used.
“We feel very comfortable shipping these eggs to other facilities,” said Kolecki.
Crystal River Hatchery also has thousands of large trout to replenish its brooding stock. Because whirling disease affects only young fish, the brooding stock isn’t immediately threatened.
Unlike many other hatcheries in the state, Crystal River Hatchery doesn’t contribute largely to the state’s program of stocking catchable-sized trout in the wild. Crystal River contributes about 35,000 trout annually to stocking programs.
In comparison, the Rifle Falls Hatchery near the town of Rifle contributes 600,000 to 700,000 catchable trout annually. That facility was recently declared free of whirling disease.
In total about 3.1 million fish will be stocked in Colorado this year.
Although officials don’t believe the exposure to whirling disease was great, the wildlife division errors on the side of caution once a hatchery has a positive reading, said Malmsbury. In this case, all fish in the hatchery must be handled as if they could have the disease, not just the fish from the group where the infection was detected, he said.
Any fish used from Carbondale for stocking this year can only go to waters that are too warm and intermittent for trout to reproduce, according to Malmsbury.
Wildlife division officials said the agency has no doubt it can remove the whirling disease threat from the Carbondale hatchery.
“We have had considerable success cleaning these facilities up,” said Malmsbury.
Kolecki noted that in 1998 the state could only stock 183,000 trout that tested negative for whirling disease. That number has grown to three million as the division learned about offsetting the disease.
However, the battle in Carbondale will take time. Kolecki said it will be a minimum of 14 months before the Crystal River Hatchery can be declared free of whirling disease through the cleaning process it plans to use. Malmsbury said that process could be longer – and much more expensive – if current tests show spring waters are still infected with the parasite.
Scott Condon’s e-mail address is email@example.com
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