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Bass Virus: A Cause for Concern?

Traci D. George
District I Fisheries Aide
Decatur, Alabama

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Nothing is more exciting than feeling the jerk of your fishing rod when a largemouth bass snatches the bait on the end of your line.  Your rod bows over and the battle begins to get the "big one" in your grip.  The largemouth bass is one of the nation’s most popular and prized sportfish.  Because it is so popular, many concerns and questions are raised about the welfare of this premium game fish.

One concern revolving around this fish is the Largemouth Bass Virus, or LMBV. A virus is a noncellular microscopic agent capable of causing a disease. Viruses require living cells as hosts in order to grow and reproduce. More than one hundred naturally occurring viruses are known to affect fish. LMBV belongs to the family known as Iridoviridae, which is a virus frequently found in cold-blooded animals. LMBV does not infect warm-blooded animals, including humans. Therefore, fish infected by LMBV are not a human health issue. The origin of LMBV is unknown, but studies have discovered that it is 98% identical to a virus found in guppies and "doctor fish," a freshwater aquarium species imported from southeast Asia to California. It is also related to a virus found in frogs (FV-3) and other amphibians. LMBV first gained attention in 1995 when it was detected in specimens collected from a fish kill on the Santee-Cooper Reservoir in South Carolina. Since then, the virus has been found in other states including: Alabama, Arkansas, Florida, Georgia, Illinois, Indiana, Kentucky, Louisiana, Michigan, Mississippi, Missouri, North Carolina, Oklahoma,

South Carolina, Tennessee, and Texas. LMBV is also known to affect other members of the sunfish family including smallmouth bass, spotted bass, Suwanee bass, bluegill, redbreast sunfish, white crappie, and black crappie.

Certain factors usually contribute to LMBV related fish kills with stress as the main antagonist. Stressful situations include warm-water temperatures, poor water quality, or improper handling of caught fish. When exposed to these situations the fish become stressed, making them more vulnerable to death. Increased temperatures played a major role in all LMBV related kills when water temperatures ranged from 77o F to 86o F. Poor water quality and the frequent and improper handling of fish by anglers can also stress fish, thus making them more vulnerable to infection. The virus has been detected in bass that show no signs of illness, indicating that many fish may be infected without becoming sick. Fish becoming ill from the virus are usually two pounds or larger and may be seen swimming on their side just under the surface with the pectoral fin sticking out of the water. Dying fish usually exhibit these symptoms because the virus attacks the swim bladder causing the fish to lose equilibrium. The stomach area of the fish may also appear bloated or inflamed.

Other important concerns of LMBV are the impacts on fishing. Researchers do not know enough about the virus to determine if it will have long-lasting effects on bass populations. Surveys conducted on lakes following a kill indicate bass abundance remains within acceptable sampling ranges, although the number of larger fish may be drastically reduced.

Universities, private interest groups, and state and federal agencies are devoted to learning more about this virus. Universities involved include Arkansas-Pine Bluff, Auburn, California Davis, Louisiana State, Mississippi, Mississippi State, and Texas A&M. B.A.S.S. has sponsored and chaired meetings for the past two years and will do so again in February of 2002 in Little Rock, Arkansas.

There are ways that anglers can help minimize the spread of LMBV and its activation into a disease. The following list is a guideline that should be followed on all fishing adventures:

  1. Clean all boats, trailers, and equipment thoroughly after a fishing trip. The virus can survive in water for at least seven (7) days and can survive in the mucous of bass skin. 

  2. Drain all water from the bilge, bait bucket, and livewell. Tap water or a mild mixture of bleach and water can be used to clean all equipment. Allow everything to air dry.

  3. Try to stage tournaments during cooler weather.

  4. Handle bass as gently and as little as possible.

  • When handling bass, grasp the lower jaw and hold vertically. Large bass should be held by one hand on the jaw and the other hand on the belly to support the weight of the fish.
  • Try to remove hooks as quickly and gently as possible with needle nose pliers.
  • Run aerators regularly when fish are in live wells. If the temperature is 70oF or above, run aerators continuously.
  • Do not crowd fish in a live well. Crowded situations in a live well contribute to stress.
  • Change water in the live well every 2-3 hours.
  1. Do not move fish or fish parts from one body of water to another.

  2. Report dead or dying fish to the District Office.


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