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LARGEMOUTH BASS VIRUS DETECTED AT CRAWFORD STATE LAKE

Kansas becomes 18th state to document virus

Kansas Department of Wildlife and Parks (KDWP) fisheries staff have confirmed the presence of largemouth bass virus (LMBV) at Crawford State Fishing Lake in southeast Kansas. Testing of bass from the lake was conducted in response to recent declines in Crawford bass populations.

KDWP staff have begun an aggressive program of monitoring for the virus, particularly at Farlington Fish Hatchery, which uses Crawford State Fishing Lake for its water supply.
“We aren’t going to move any fish from the Farlington hatchery until testing for the presence of the virus there is completed,” said Doug Nygren, KDWP fisheries section chief. KDWP staff at fish hatcheries in Pratt and Meade also are monitoring for the virus at those facilities. Milford Fish Hatchery is currently undergoing renovation and is out of production this year.

One of more than 100 naturally-occurring viruses that affect fish, LMBV was first documented in Lake Weir in Florida in 1991, and has since occurred in 17 other states: Alabama, Arkansas, Florida, Georgia, Illinois, Indiana, Kentucky, Louisiana, Michigan, Missouri, Mississippi, North Carolina, Oklahoma, South Carolina, Tennessee, Texas, and Virginia.

KDWP biologists, like other fisheries scientists around the country, are working to learn more about the virus and its impact on the resource. Scientists do not know enough yet about the virus to determine if it will have long-lasting effects on bass populations although it appears from early occurrences across the U. S. that it does not cause long-term harm to fisheries.

While other fish species -- including smallmouth bass, spotted bass, bluegill, white crappie, and black crappie -- have been infected with the virus, it has so far proved to be fatal only for largemouth bass.

“It’s troubling for a variety of reasons,” Doug Nygren said. “Largemouth bass are among the most popular sportfish species in Kansas, so any incident that reduces bass populations is cause for concern. And while we and our counterparts around the country are learning more about the virus every day, there are many unknowns.”

LMBV is not readily apparent in fish. Infected fish typically show no signs of the disease and appear completely normal. Adult bass of 2 pounds or more seem to be the most susceptible to the virus. Summer water temperatures appear to be one variable that increases the lethality of the virus; almost all bass die offs documented in other states have occurred from June through September. Scientists do not know how the virus is transmitted or how it is activated into a disease, and no cure is currently known.

The virus is not known to infect any warm-blooded animals or humans. Common-sense precautions are recommended, such as thoroughly cooking any fish and not consuming fish that are found dead or appear sickly.

While there has not been a sudden die-off of largemouth bass at Crawford, fisheries monitoring there revealed a substantial decline in bass populations the past two years. One result has been a proliferation of undesirable fish species, such as carp and bullhead catfish, presumably the result of reduced predation by largemouth bass.

Anglers can help minimize the spread of LMBV and other fish diseases and aquatic nuisance species by consistently applying the following precautions:

  • because the virus can live for several hours in water, clean boats, trailers, and other equipment thoroughly between fishing trips to keep from transporting undesirable pathogens and organisms from one water body to another;
  • never move fish or fish parts from one body of water to another, and do not release live bait into any flowing or impounded water;
  • handle bass as gently as possible if you intend to release them;
  • conduct fishing tournaments during cooler weather, so fish caught will not be excessively stressed; and
  • report dead or dying fish to any KDWP office.

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