Virus found in five Kansas lakes; long-term impact unknown

FARLINGTON -- In 2007, Kansas Department of Wildlife and Parks (KDWP) fisheries staff 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 a decline in the population. Now, four other lakes in the state have tested positive for the virus: Big Hill Reservoir (east of Cherryvale), Gardner City Lake (north of Gardner), Lonestar Lake (southwest of Lawrence), and Woodson State Fishing Lake (east of Toronto).

KDWP staff have been screening for the virus, particularly at Farlington Fish Hatchery, which uses Crawford State Fishing Lake for its water supply.

LMBV is caused by an iridovirus and has been identified in at least 18 other states, including Alabama, Arkansas, Georgia, Illinois, Indiana, Kentucky, Louisiana, Michigan, Missouri, Mississippi, North Carolina, Oklahoma, South Carolina, Tennessee, Texas, Virginia, Utah, and Wisconsin. 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 about it to determine if the virus will have long-lasting effects on bass populations. Studies throughout the U.S. suggest 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 in largemouth bass.

Infected fish typically show no signs of the disease and appear completely normal. Adult bass weighing 2 pounds or more seem to be the most susceptible. Summer water temperatures and stress appear to increase 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 sick.

While there has not been a sudden die-off of largemouth bass in any of these lakes, monitoring at Crawford revealed a substantial decline in bass numbers in 2006 and 2007; however, numbers of young fish increased in 2008, so biologists hope the population will rebound naturally. 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, other fish diseases, and aquatic nuisance species by always following these precautions:

• because the virus can live for several hours in water, anglers should clean boats, trailers, and other equipment thoroughly between fishing trips to keep from transporting undesirable pathogens and organisms from one water body to another, and live wells should be cleaned with a bleach solution (1/8-cup bleach to 1 gallon of water) and thoroughly dried;
• never move fish or fish parts, including skeletal parts and entrails, 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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