Largemouth Bass Virus in New Hampshire
Updated April 2013
Click here to skip to LMBV prevention guidelines for anglers
What is Largemouth Bass Virus?
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.
Has LMBV been detected in New Hampshire?
In 2007, smallmouth bass collected during the summer from Lake Winnipesaukee by the New Hampshire Fish and Game Department tested positive for LMBV. "It is probable that the virus exists in other water bodies 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," said Gabe Gries,
N.H. Fish and Game fisheries biologist and the Department's Warmwater
Project Leader.
The previous year (2006), largemouth and smallmouth bass collected during the summer by the New Hampshire Fish and Game Department had tested negative. Bass examined that year included 10 from the Connecticut River, 16 from Winnisquam Lake and 58 from Lake Winnipesaukee.
To date, where has LMBV been found?
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 since been detected in some Northeastern states. These include Vermont (Lake
Champlain), Connecticut, and New Hampshire (where it was detected in 2007 in Lake Winnipesaukee).
What role can anglers play in limiting the spread of LMBV?
Because the virus can sometimes kill or otherwise negatively
impact largemouth bass and can be spread or influenced by anglers,
it is critical that anglers become educated about how they can help prevent the spread of this virus. (Click here to skip to LMBV
prevention guidelines for anglers)
Impact on the fishery
Presence of the virus in a fish population does not necessarily
mean fish will develop LMBV disease, which can cause them to 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.
How is LMBV transmitted, and what waterbodies
have been tested?
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 has tested waterbodies with high inter-state boat traffic, including Lake Winnipesaukee (2006 and 2007), Lake Winnisquam (2006) and the Connecticut River (2006). Testing occurred during the summer, when the virus/disease is known to be most active. N.H. Fish and Game worked with bass clubs holding tournaments on these waterbodies to collect fish samples.
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 with a solution of bleach to water (1:100 ratio) and let air-dry.
- Never transfer fish or fish parts from one
body of water to another. In fact, N.H. 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 on warmwater fisheries management in N.H., 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; or email
gabe.gries@wildlife.nh.gov.
Click to read N.H. Fish and Game press statements regarding LMBV:
- August 28, 2007-- Largemouth Bass Virus Found in Lake Winnipesaukee
- Dec. 1, 2006 -- N.H. Bass Test Negative for Largemouth Bass Virus
- June 20, 2006 -- Fish and Game to Test for Largemouth Bass Virus
Click here for more information on warmwater fisheries management in N.H.
