September 30, 2010
Largemouth bass virus took its toll on this classic Missouri bass lake, but things seem to be back to normal. That means plenty of largemouth action for anglers.
By Spencer E. Turner
Have you ever watched a friend suffer a serious health problem, then agonize as you witness the struggle to recover some semblance of the once vibrant self? Table Rock Lake suffered a devastating stroke to its bass population and is now fighting to recover its former greatness. Table Rock Lake was, and will be in the future, one of Missouri's aquatic jewels, spilling out gems in the form of largemouth and smallmouth bass to anglers willing to test her waters.
Join me as we trace this illness, visit with Dr. Scott Syska, D.V.M., and Bill Anderson, Table Rock biologist, to learn what has happened and what anglers can expect in 2002.
HISTORY OF AN ILLNESS Beginning in late summer and fall of 1999, bass anglers began to report seeing large bass floating dead in the James River arm of Table Rock Lake. Although some fish die every year from a variety of causes, including disease, usually the loss is small and well absorbed into what biologists call natural mortality. All animals die, including you and me; some die young, others old. In bass populations, this usually amounts to 15 percent or less of the population each year. What wasn't typical was the size of the bass dying in 1999 from this mysterious malady.
By fall, the die-off had spread, not only up the James River arm, but also to the Kings River arm and other lake areas. Table Rock Lake had a serious problem.
Bill Anderson, Table Rock Lake biologist, and Dr. Scott Syska, D.V.M., Missouri Department of Conservation pathologist, began collecting samples of the dead bass and making counts to get a handle on how large the die-off was and what was causing it. Syska and Anderson found that dead bass in Table Rock Lake had epistylis (external protozoan that irritates the skin of fish), aeromonas, (a bacterial infection), and peritonitis. Most fish displayed red sores, but none had typical symptoms of largemouth bass virus (LMBV). Dr Syska says that in LMBV kills, there are usually no signs of other diseases.
"In real LMBV die-offs, bass are found struggling on the surface, then they die," says Syska. "When you cut them open, you see increased redness of the swim bladder, some fluid buildup, and plaque in the swim bladder."
Photo by Keith Benoist
To help with his diagnosis, Syska sent tissue samples to Dr. John Grizzle at Auburn University, the leading expert on LMBV disease. Grizzle found that, in fact, the dead bass from Table Rock had LMBV. At the time (1999), Table Rock Lake was one of the northernmost lakes afflicted by LMBV, a very common virus found in southeastern and southern lakes such as Lake Fork in Texas. What he or Syska could not say was whether LMBV had killed the bass, or whether the bacterial infections that had become systemic were the culprit.
Dr. Syska believes, as does Bill Anderson, that the fish kill was caused by a combination of factors. "It's likely the virus make bass more susceptible to other diseases," says Syska. "That would explain why the large individuals get other diseases and die. We have seen big epistylis outbreaks in lakes where LMBV has not been seen, but the fish weren't dying. They just get the big red sores, then heal. So in Table Rock, it's easy to theorize that LMBV had something to do with the 1999 die-off of large bass.
"We think LMBV was originally in the southeast United States and has spread from there. Some people are asking if we are just noticing it now, or if it is a mutated virus. In other words, is it new or is it old? Nobody knows. If you're asking where it came from here in Missouri, the most likely cause is illegal fish stocking, but we don't know that for certain. Nobody has come forward and said they illegally stocked bass here in Missouri."
Syska and other pathologists believe that LMBV is found in other fish also, but it isn't detrimental for those species. "Researchers have found that LMBV is carried mostly by centrarchids (members of the sunfish family), and recently they have found at least one case in the southeast where a Morone (member of the striper family) carried it. LMBV death is pretty much limited to big bass. Researchers can also detect it in small bass. And when a researcher finds a kill, the kills are usually associated with other problems, along with the virus."
Syska notes that since the 1999 outbreak of LMBV in Table Rock Lake, he has discovered the virus in Lake of the Ozarks, Truman Lake, Lake Wappapello and Lake Springfield, with additional studies from other Missouri Lakes still pending.
Although 1999 was a devastating year for large bass in Table Rock Lake, the future looks good, according to Bill Anderson, lake biologist. Within a year after the outbreak, Anderson's electrofishing surveys of the bass population, as well as information from bass tournaments, anglers and dock owners on the lake showed that the disease had eliminated most large bass over 15 inches in Table Rock Lake. Small bass didn't seem to be as affected, but large bass, legal bass and trophy bass certainly were.
The once great bass fishery had suffered a serious setback. When, if ever, would Table Rock bass fishing bounce back to some semblance of its former greatness? When could anglers once again experience the thrill of catching a trophy bass from Table Rock's fabled waters? I asked Bill Anderson after he had completed his 2001 bass sampling in Table Rock Lake. His answers were extremely heartening.
"In 1999, the dead bass we found were all large," says Anderson. "I found all large fish, 3 pounds up to fish over 9 pounds. It really hammered the large bass in Table Rock Lake. But the thing is, Table Rock Lake is recovering very rapidly. I caught two largemouth bass over 4 pounds this last week (last week of December 2001).
"My sampling in 2001 in the James River Arm showed really high numbers of largemouth bass in the population from a huge 1999 year-class. You have to keep in mind that biologists aren't able to sample large bass very efficiently because they just don't like to get shocked. When the lake is low, as it has been the past two years, big fish just don't sit on bare banks and let you run over them with a boat. I'm talking about fish 5 pounds and larger. We can't even detect in our samples that we had a fish kill in 1999. But we don't sample that bigger component of the population very well. But the year-class coming on in the James River Arm is just incredible. We had a tremendous 1999 year-class.
"Largemouth bass in the 1999 largemouth bass year-class will be 15 to 17 inches in length in 2002. They've had three growing seasons, and faster-growing bass are already hitting 15 inches. I reall
y think lake-wide fishing is looking good. I'll be the first to admit we don't have the numbers of lunker largemouth bass we once had - bass over 4 pounds - but populations ebb and flow, and I'll be darned if I'm going to stock bass as some anglers have requested. We are still not back to the numbers of lunker bass we once had, but we're making progress . . . lots of 3- and 4-pound fish."
As I listened to Anderson talk about Table Rock Lake and his experiences sampling and fishing the lake, I realized just how good the fishing was right now and what the future had in store. Anglers can be thankful we have dedicated scientists like Syska and Anderson looking out for our interests. Largemouth bass fishing will be great in 2002, but look out in 2003. Table Rock Lake will be back in all of her glory.
Anderson asks that if you observe any dead or dying bass while fishing Table Rock Lake or any other Missouri lake, report the fish kill to Fisheries, Missouri Department of Conservation, P.O. Box 180, Jefferson City, MO 65102, phone (573) 761-4115.
UNDERSTANDING 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 found near the surface, having trouble swimming and remaining upright because LMBV attacks the swim bladder, causing loss of equilibrium. Diseased fish may appear bloated, and stressed bass will be larger than 2 pounds.
Researchers have found LMBV in members of the sunfish family, which includes largemouth, smallmouth and spotted bass, but so far it is only fatal for large largemouth bass. It has the potential to cause minor and sporadic fish kills.
To help stop the spread of LMBV, drain all water from your bilge and livewells and clean your boat, trailer and other equipment between fishing trips. Do not transport and stock fish or fish parts from one body of water to another.
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