Largemouth bass virus (LMBV) is a disease that impacts several fish species but only appears to cause death in some largemouth bass. First discovered in Florida in 1991, LMBV spread throughout the southern United States and was responsible for a number of largemouth bass deaths in the late 1990’s. However, in some reservoirs LMBV only led to a decrease in survival and growth rates. When those declines occur, anglers catch fewer quality-size (greater than three pounds) largemouth bass. The good news is that impacts from the virus outbreak are normally short lived and largemouth bass fisheries recover in about three years.
The Virginia Department of Game and Inland Fisheries (VDGIF) and the North Carolina Wildlife Resources Commission (NCWRC) tested several reservoirs between 2000 and 2003 with most either having no occurrence of LMBV or very slight infection rates. However, in a few reservoirs in North Carolina almost 40% of the largemouth bass tested were positive for LMBV. One of those systems was Shearon Harris Reservoir, which continues to support one of the best largemouth bass fisheries in the state.
Recent virus testing coordinated by VDGIF this past August revealed that LMBV was present in about 40% of the bass tested at John H. Kerr Reservoir/Buggs Island Lake and is responsible for the decline in the bass fishery. Largemouth bass from Briery Creek Lake and Sandy River Reservoir (Prince Edward County) were also tested and the virus was detected and confirmed. A small largemouth bass mortality event which occurred at Briery Creek Lake in late June, 2010, was most likely the result of LMBV in the population.
Due to the popularity of the largemouth bass fishery at Kerr Reservoir/Buggs Island Lake, anglers have expressed concerns about the LMBV spreading to other area reservoirs. However, some of the area reservoirs already contain LMBV and fish have likely built-up an immunity to the virus. For example, largemouth bass in Lake Gaston tested positive for LMBV in 2000. However, recent surveys at Lake Gaston indicate that the largemouth bass population is doing well.
Nevertheless, VDGIF recommends that anglers follow the precautions listed below to limit the spread of LMBV.
Largemouth Bass Virus FAQ:
Can the disease be cured?
No, the virus will have to run its course and hopefully the fish will build up immunity to LMBV. So far, lakes affected by the disease in the southern U.S. have not experienced additional large LMBV outbreaks since the initial ones in the late 1990’s.
Are there any risks to humans from the virus?
No, fish are safe to eat and the water is safe for drinking water supply and recreation. This virus cannot be passed to humans.
What causes an outbreak of the virus?
It is not fully understood what causes an outbreak of LMBV. It is likely that stressful conditions such as low reservoir levels, high water temperatures, or increased handling time make bass more susceptible to LMBV.
How can you tell if a largemouth bass that you’ve caught has the disease?
There are very few external cues that the bass might have the disease. Fish that are very sick from the virus may appear bloated and swim erratically due to the impacts of the virus on the swim bladder.
How does the disease spread?
Fish that come in close contact (like in a livewell) can easily infect one another. Transmission through the water and eating infected prey are also ways that the disease is spread.
What can anglers do?
* Limit fishing, especially tournament fishing, to cooler months. Bass with LMBV are more likely to suffer mortality in the heat of the summer due to stress related to the high water temperatures. Paper tournaments without weigh-ins are always on option that tournaments can explore for summertime tournament fishing.
* Cooling livewells with blocks of ice in summer months is highly recommended. But, do not decrease water temperature in livewells more than 20° F from reservoir water temperatures.
* DO NOT transfer fish or fish parts from one body of water to another. This can spread the virus.
* Land fish quickly and handle them gently to avoid exhaustion and capture stress. Return the fish quickly to the water if you do not plan to keep it.
* Sterilize bilge pumps and livewells with a bleach solution to kill the virus. Studies have shown that the virus can survive in water in livewells up to seven days. About 1.5 fluid ounces of bleach added to one gallon of water (1% solution) sprayed on livewell surfaces will kill the virus. Let the bleach solution stand for 5 minutes, rinse thoroughly, and let air dry as chlorine bleach is toxic to fish.
* Tournaments should adopt best handling practices at all events. Using release boats, resting stations with oxygen and/or recirculating water, and iced water are all important considerations when planning a tournament. Refer to the conservation pages of the TBF or BASS websites for more information on safe handling practices and tournament organization guidance.
source: Virginia Department of Game and Inland Fisheries