B.A.S.S. Convenes Second National Largemouth Bass Virus Workshop

 

JACKSONVILLE, Fla. --- While many questions remain unanswered regarding the Largemouth Bass Virus (LMBV), researchers are more confident than ever that the illness will not destroy Americašs bass fisheries.

Yes, some largemouth bass did die from the virus during the year 2000. But the number of kills remained at less than a dozen, nearly the same as 1999.

Additionally, the number of individual bass fatalities with each incident remained relatively small, and no lakes or reservoirs have sustained kills two years in a row.

Those were some of the revelations shared during the second annual LMBV Conference convened here by B.A.S.S., Inc. More than 75 fisheries biologists, pathologists, veterinarians and other experts from universities and state and federal agencies sat in on the all-day session.

Despite their belief that LMBV outbreaks are not likely to grow to catastrophic proportions, scientists still want to solve the mystery of what makes the virus turn suddenly from just being detectable into a deadly disease. Such knowledge, they say, could help prevent further outbreaks, an objective that not only would benefit the resource but reassure bass fishermen nationwide.

"Anglers think it's serious, so it's serious," said Phil Durocher, Texas fisheries chief, in explaining why his state is researching LMBV so determinedly. Texas biologist David Terre said that the Lone Star State has begun a statewide survey of 49 reservoirs. Thus far, bass in only 8 of 31 fisheries analyzed have tested positive, with all of them in central or east Texas. The most notable are Fork, Sam Rayburn, Toledo, and Conroe, where bass died in previous years, but not during 2000. In fact, Texas researchers found no kills related to the virus last year.

"We obtained the equipment and expertise to test for LMBV," said Terre.

"Also, we continued our investigation into hatcheries and into the kills on Fork and Rayburn.

"Electrofishing surveys didn't show that populations in Fork and Rayburn were seriously impacted," the biologist added. "But anglers felt the impact. There is no question that tournament catch rates were off. There was a measurable effect on catch rates."

In addition to the Texas Parks and Wildlife Department, leaders in LMBV research include the federal Warm Springs, Georgia Fish Health Center, Mississippi State University, and Auburn University.

At Auburn, scientist John Grizzle and his associates made one of the most important findings of the year regarding the virus: LMBV can remain viable in water for at least three to four hours. "Tentatively, that means you could transport the virus in a livewell," he said.

One of LMBV's biggest mysteries has been how it is moved from lake to lake, with fish-eating birds and fishermen both among the suspects. The Auburn finding reinforces the advice given to anglers by state agencies to empty all water from livewells, bilges, and bait buckets before moving boats from one lake to another.

The Auburn team also discovered, that bass could contract the virus from guppies experimentally infected with LMBV, suggesting that transmission also can occur orally.

Just as big a puzzle as how the virus is spread has been what triggers it to turn fatal. Stress and warm water have been among the leading suspects.

But this past summer, LMBV killed fish in Lake George, a 525 acre natural lake, on the Indiana-Michigan border, where the water temperature was no more than 72 degrees. Before that, LMBV kills had been confined to an area from east Texas to North Carolina and south from Table Rock Lake on the Missouri-Arkansas border. Scientists had thought the virus might not threaten fish in more northern waters. But it has.

"There's not a lot of local concern, and we won't start sampling (looking for presence of the virus in other lakes) unless it starts showing up (causing fish kills) in other lakes," said Gary Whelan of the Michigan Department of Natural Resources.

Other kills did occur during 2000 in Arkansas, Oklahoma, and Louisiana.

Probably the most notable was on Lake Monticello, considered by many to be Arkansas premiere trophy bass lake.

Arkansas biologist Jon Stein said about 1,000 adult bass, most of them 16 to 24 inches long, died in the 1,400-acre lake from June into September. The largest found weighed 12 pounds.

"In August, the number of infected bass was at its peak," he said, adding that fish in lakes Dardanelle and Ouachita also tested positive for the virus, while fish in Millwood proved negative.

Just across the border in Oklahoma, LMBV-related kills occurred in Tenkiller, Grand, Hudson, and Fort Gibson.

But despite drought and low-water conditions that no doubt stressed bass in many lakes and reservoirs throughout the South this past summer, LMBV die-offs did not increase, workshop attendees emphasized, adding that's the best news of the year.

On the down side, research progress has been limited, mostly because of financial constraints. Researchers are optimistic that four LMBV projects totaling about $500,000 will be funded in the coming year with Federal Sportfish Restoration Funds that have been reverted from the states back to the U.S. Fish and Wildlife Service. These are the revenues collected from excise taxes on fishing tackle and motor-boat fuel paid by anglers and boaters.

Contact B.A.S.S. Conservation Department at (334)272-9530 or via e-mail to conservation@bassmaster.com for more information.

 

FACT SHEET:

LARGEMOUTH BASS VIRUS WORKSHOP SPONSORED BY B.A.S.S., INC.

JACKSONVILLE, FLORIDA

FEBRUARY 22, 2001

1. What is Largemouth Bass Virus?

It is one of more than 100 naturally occurring viruses that affect fish but not warm-blooded animals. Origin is unknown, but it is related to a virus found in frogs and other amphibians and nearly identical to a virus isolated in fish imported to the U.S. for the aquarium trade. Although the virus apparently can be carried by other fish species, to date, it has produced disease (death) only in largemouth bass. Scientists do not know how the virus is transmitted or how it is activated into a fatal disease. In addition, they know of no cure or preventative, as is commonly the case with viruses.

LMBV first gained attention in 1995, when it was implicated in a fish kill on Santee-Cooper Reservoir in South Carolina. Since then, the virus has been found in impoundments throughout the South and, during 2000, was confirmed as the source of a kill in Lake George on the Indiana-Michigan border.

Often, the virus has been detected in bass that show no signs of illness, which suggests that some fish might be infected but not ever become sick.

Some kills, however, have been linked to LMBV. Since all those die-offs occurred from June through September, warm-water temperatures might be a factor, particularly in southern fisheries, where surface temperatures can remain in the 90s for months at a time. No other common variables seem to exist among lakes where kills occurred. Some lakes, for example, contain aquatic vegetation and others do not, suggesting that herbicide management of aquatic plants did not trigger the disease to turn fatal.

Some scientists believe that "stressed" bass might be the most likely to die of the disease. Along with hot weather, stress factors might include poor water quality caused by pollution and frequent handling by anglers.

Thus far, LMBV-related kills have been minor in comparison to kills prompted by other causes, such as pollution. These largemouth bass die-offs have received considerable attention, however, because they involve the nation's most popular game fish.

No evidence presently exists that LMBV has caused a long-term problem on any fishery or that it will have a long-term impact.

2. What are the signs of Largemouth Bass Virus?

Most bass infected with LMBV will appear completely normal. In those cases where the virus has triggered disease, however, dying fish will be near the surface and have trouble swimming and remaining upright. That's because LMBV appears to attack the swim bladder, causing bass to lose their equilibrium.

Diseased fish might also appear bloated.

Adult bass of two pounds and more seem to be the most susceptible to disease, or at least the most visible.

3. Is Largemouth Bass Virus a new disease?

No consensus exists on this question! Because LMBV has been confirmed in so many places at nearly the same time, some scientists suspect the virus has been around for awhile. Others suggest that "genetic sequencing information" indicates that it may be relatively new.

4. Where has Largemouth Bass Virus been found?

Since 1995, LMBV has been found in 15 states: Alabama, Arkansas, Florida, Georgia, Indiana, Kentucky, Louisiana, Michigan, Missouri, Mississippi, North Carolina, Oklahoma, South Carolina, Tennessee, and Texas. Other states, including Maryland and Virginia, have monitored for the virus, but did not find it. Others plan to do so in 2001. Between March and November 2000, researchers examined 3,476 largemouth bass and related sunfish species in nine southeastern states, according to the federal Warm Springs Fish Health Center. Of those, 464, or 13 percent, tested positive for LMBV. Fish kills attributable to LMBV have been confirmed in nearly 20 locations.

During 2000, fish died in Arkansas' Monticello, as well as Louisianašs False River and Oklahoma's Grand, Tenkiller, Hudson and Fort Gibson lakes. Kills also have occurred at Santee-Cooper, S.C. (1995); W.F. George Reservoir (also known as Lake Eufaula), Ala. and Ga. (1998); Greenwood Reservoir, S.C. (1998); Sardis Reservoir, Miss. (1998); Sam Rayburn, Texas (1998); Lake Fork and Lake Conroe, Texas (1999); Toledo Bend, Texas and La. (1999); Table Rock Lake, Mo. and Ark. (1999); Lake Ferguson and Tunica Cutoff, Miss. (1999), and Atchafalaya Basin, La. (1999).

5. What are the impacts to bass populations?

Scientists do not know enough yet about the virus to determine if it will have long-lasting effects on bass populations. Indications are, however, that it will not harm fisheries long term. Surveys on lakes following a kill suggest that fish populations remain within the normal range of sampling variability.

6. What are the impacts to fishing?

Following some kills, anglers have reported catching fewer bass, especially bigger fish. But indications are that an infected fishery will recover within a year or two.

More largemouth bass are killed annually by other known diseases than by LMBV.

7. Are other fish and animals affected by Largemouth Bass Virus?

LMBV is a virus of the type that affects only cold-blooded animals.

Researchers have found it in other members of the sunfish family, which bass belong to, but, thus far, it has proven to be a fatal disease only for largemouth bass. Other members of the sunfish family found infected with the virus include smallmouth bass, spotted bass, Suwanee bass, bluegill, redbreast sunfish, white crappie, and black crappie.

Amphibians, reptiles, and other fish species could be carriers of LMBV.

Scientists have found LMBV to be 98 percent identical to a virus found in guppies and "doctor fish," a freshwater aquarium species imported from southeast Asia. This suggests that LMBV could have originated with importation of an exotic species.

8. Are infected fish save to handle and eat?

Yes. LMBV is not known to infect any warm-blooded animals, including humans.

But common sense should prevail at all times: Thoroughly cook fish that you intend to eat. Also, fish that are dead or dying should not be used for human food, regardless of the cause of the illness.

9. What can and is being done?

As with many fish viruses, little is known about LMBV. But because of the popularity of largemouth bass, state and federal agencies, universities, and private interest groups are working hard to learn more about the virus and its impact on the resource. Universities involved with LMBV 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 in 2000 and 2001 to bring all the managers and researchers together. This will be repeated in 2002.

10. What do the experts think?

Because so little is known about LMBV, scientists have few conclusions to offer regarding the virus. They do suggest, though, that LMBV probably will become an enduring element in ecosystems and a component in natural selection. In other words, it could serve as a population control. On the positive side, scientists believe that LMBV does not appear to have the potential to cause anything more than minor and sporadic fish kills.

11. What anglers can do?

Anglers can help minimize the spread of LMBV virus and its activation into a lethal disease by doing the following:

--- Drain all water from the bilge and livewells and clean boats, trailers, and other equipment thoroughly between fishing trips to keep from transporting LMBV--- as well as other undesirable pathogens and organisms--- from one water body to another. Recent research has determined that the virus can live for several hours in water, confirming the importance of this practice.

--- Do not move fish or fish parts from one body of water to another. And do not release live bait into a fishery.

--- Handle bass as gently a possible if you intend to release them.

--- Stage tournaments during cooler weather, so fish caught will not be so stressed.

--- Report dead or dying fish to state wildlife agencies.

--- Volunteer to help agencies collect bass for LMBV monitoring.

--- Educate other anglers about LMBV.