Gabe Gries, (603) 352-9669
Scott Decker, (603) 271-2501
Jane Vachon, (603) 271-3211
June 20, 2006

Fish and Game to Test for Largemouth Bass Virus

CONCORD, N.H. -- This summer the New Hampshire Fish and Game Department will test fish for the presence of largemouth bass virus (LMBV), one of more than 100 naturally occurring viruses in fish. Fish with largemouth bass virus are safe to handle and eat, as the virus does not infect warm-blooded animals, including humans.

"Because the virus can sometimes kill or otherwise negatively impact largemouth bass and can be spread or influenced by anglers, it is important to test fish to learn if the virus is present in New Hampshire, educate anglers about the virus and try to minimize its spread," said Gabe Gries, N.H. Fish and Game fisheries biologist and Warmwater Project Leader.

Largemouth bass virus was first detected in Florida in 1991 and gained national attention in 1995 when it was found to be the cause of a largemouth bass kill in South Carolina. The virus was originally thought to be restricted to the southern U.S., but it has recently been detected in some Northeastern states, including Vermont (Lake Champlain) and Connecticut. According to Gries, LMBV has not been detected in New Hampshire, but so far only three waterbodies have been tested, and it is probable that the virus exists in the state. "However based on the information we have to date, it is unlikely that largemouth bass virus poses a serious threat to the long-term health of New Hampshire's bass resources," Gries said.

Presence of the virus in a fish population does not necessarily mean fish have the disease or will die or show signs of being in poor health. The virus appears to result in disease when largemouth bass are stressed; warm water temperatures, low oxygen, poor water quality and frequent handling can increase the chance that fish may exhibit the disease. Although the virus can be carried by other fish species, such as smallmouth bass, chain pickerel, redbreast sunfish, black crappie and bluegill, it is only known to be fatal to largemouth bass. The ability of other species, such as baitfish, to carry the virus is unknown.

Most fish carrying largemouth bass virus appear completely normal, but largemouth bass kills sometimes result in waters that test positive for LMBV. These fish kills generally occur during the summer months, indicating that warmer water temperatures may be a factor. In cases where the virus has triggered disease, dying bass may be near the water surface and have difficultly swimming and remaining upright. The virus attacks the swim bladder, sometimes causing bass to lose their equilibrium and appear bloated. Largemouth bass between 12 and 15 inches appear to be most susceptible to the disease. The occurrence of lesions or black spots is not necessarily a sign that a fish has LMBV.

No evidence currently exists that the virus has caused long-term impacts to a fishery; some data indicate that an infected fishery will recover over a period of years. Scientists are unsure as to how the virus is transmitted or how it is activated into disease. There is currently no cure or preventative for LMBV, and it can live in water for up to seven days. The virus may be transmitted through water, by fish consuming infected prey, or through direct and indirect contact in boat live wells.

The N.H. Fish and Game Department plans to test some waterbodies that have high inter-state boat traffic, including Lake Winnipesaukee, Lake Winnisquam and the Connecticut River. Testing will occur during the summer when the virus/disease is known to be most active. "We hope to work with bass clubs holding tournaments on these waterbodies and use any tournament-associated fish mortalities for our samples," said Gries.

Anglers can help minimize the impact and spread of largemouth bass virus by following these suggested guidelines:

  • Drain water from bilge and live wells and clean boats, trailer and other equipment between fishing trips.
  • Do not transfer fish or fish parts from one body of water to another. In fact, NH law prohibits transfer of live fish from one water to another.
  • Do not release live bait into waterbodies.
  • Handle bass as gently as possible.
  • During times of high water temperatures, minimize stress to fish as much as possible.
  • Conduct fishing tournaments during cooler weather, so fish caught will not be as stressed.
  • Reduce daily bass tournament bag limits or use a "paper format" during times of high water temperatures.
  • Report dead or dying fish to the N.H. Fish and Game Department.
  • Educate other anglers about LMBV.

For more information, contact:
Gabe Gries, Fisheries Biologist II/Warmwater Project Leader, New Hampshire Fish and Game Department, Region 4, 15 Ash Brook Court, Keene, NH 03431; phone 603-352-9669; fax: 603-352-8798; or email:

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