|
||||
  
 
 |
Whirling disease is here, but not hurting Utah as badly as it has neighboring states By
Eric Buchanan
The Logan River used to be free from whirling disease, which can deform or kill trout or salmon. But a test taken last fall to determine the presence of the disease came up positive. A fish that gets the disease can show symptoms such as a curved spine, a deformed jaw, a blackened tail or the tendency to swim in circles in a whirling motion. To most people, this might not mean much. Humans can't get the disease because it is specific to trout and salmon. However, the disease has the potential to adversely affect business in the fishing industry. Art Butts, a graduate student at Utah State University with the fisheries and wildlife co-op, is studying whirling disease and working on whirling disease projects in Cache Valley. He said there has been a definite economic hit in Montana and Colorado. "Wild rainbow (trout) are almost nil there, and that's hurt a lot of outfitters," Butts said. "Utah hasn't seen a lot of effects from it yet." Other Cache Valley sites where whirling disease has been found are Hyrum Reservoir, Porcupine Dam and the Blacksmith Fork River. Grant White, of Willow Valley Sportsman, said the disease has been detected on the Sportsman's fishing ranch but hasn't affected the fish. "The DWR and the fisheries and wildlife resource department at USU are working together studying the ranch to see why it hasn't affected them," White said. "It may not be as bad as it's being talked up to be." White said Willow Valley Sportsman hasn't lost business because of the disease. Bob Lauriski, of Rivers Wild Outlet Store, said his store has not experienced a decline in business because of the disease. He said most customers know about it and aren't bothered by it. "They ask about it and we hear about it, but they'll usually go (fishing) regardless," Lauriski said. Butts said the test last fall was the first sufficient sample to be taken from the Logan River. This mean the disease could have been i the water for months or years before the test was taken. In 1999, a group called Trout Unlimited put out a booklet titled "Whirling Disease in the United States: A Summary of Progress in Research and Management." Butts said this is what he gives anyone who has questions about whirling disease. The booklet said the disease was discovered in 1893 by Dr. Bruno Hofer, who reported it in rainbow trout in Germany and named the parasite that causes the disease Myxobolus cerebralis. Relative resistance to the disease observed in brown trout suggest that the parasite originated in that fish in Europe. The booklet said the report was found in the United States in 1958 at the Benner Spring Fish Research Station in Pennsylvania. It was speculated that M. cerebralis arrived there in 1956 through a shipment of frozen trout from Europe. Since then, the parasite has been found in hatcheries or in the wild in 22 states. The full 35-page report of Trout Unlimited can be found at www.tu.org/library/conservation.html. The organism of whirling disease has a complex life cycle. Tubifex worms dwelling on the bottom of a body of water ingest the M. cerebralis. When the parasite is inside the worm, it changes into Triactinomyxons (TAMs), the form that infects trout. The TAMs, "shaped like little grappling hoods," according to Butts, are released into the water. A healthy trout can be attacked by eating a Tubifex worm or from a TAMs hooking onto its body. Either way, the TAMs travel to the fish's central nervous system and begin to attack young cartilage. When a fish comes in contact with the disease, it may not show immediate signs of infection. Older fish that come in contact may be only carriers. Butts said younger fish are more susceptible because the disease attacks growing cartilage and the young fishes' bodies are still developing. Once that TAMs have gotten into the cartilage, they develop into a mature spore. When the fish dies or is eaten by a predator, spores are released into the water and the process begins again. Trout Unlimited is encouraged by research, but Butts said he isn't sure there will be a cure. Butts emphasized that even if a person eats the fish, he or she would not get sick. "The pathogens in the disease are used to the cold and couldn't live in our warm bodies," he said. People may not be affected by the disease, but they can unknowingly spread it. The Utah Division of Wildlife Resources encourages anglers to clean mud off equipment such as waders, boats, float tubes and fins before leaving a fishing spot. The M. cerebralis settles into silt and fine mud and be carried by dirty equipment. The DWR also encourages peopel who fish to dry their equipment in the sun, as ultraviolet rays kill the parasite. Using a chlorine-based cleaner also can kill the parasite. Anglers can also carry the disease by catching a fish and letting it go, further upstream, or cleaing a fish in a different body of water than the one where it was caught. According to the TU report, the DWR has taken several steps in response to the threat. State hatcheries close to waters known to have the disease are being tested twice yearly. In streams that have tested positive for the disease, managers have tried to avoid stocking rainbow trout and using large brown trout where possible. There has also been a substantial education initiative using brochures, bumper stickers and signs. The report said that fish health policy will be established by a Utah
fish health board. The six-member board will consist of two representatives
of the DWR, two representatives of the Utah Department of Agriculture,
one angler and one private aquaculture representative. This board will
shape future policy decisions. |
Archived Months:
January
1999 January
2000 |
||