On June 24, 1999, officers of the Inland Fisheries department in Tyler, Texas, received an extraordinarily distressing phone call. According to a local fishing guide who telephoned the office that afternoon, a host of dead largemouth bass had been seen floating in Lake Fork – a pristine bass fishing lake, located approximately 70 miles east of Dallas, that holds 15 of the top 20 Texas largemouth bass state records.
While the report of dead fish was disturbing in and of itself, the fact that the cause of death was unknown was even more unsettling. However, there was a potentially more unnerving question yet to be answered. Could the Lake Fork die-off be related to the tragic events surrounding the 1995 fish kill in the Santee Cooper reservoir system in South Carolina – where nearly 1,000 largemouth bass were killed as a result of a mysterious virus – or the 1998 virus-related fish kill in Mississippi’s Sardis Reservoir where over 6,000 largemouth perished?
With more questions than answers, Texas authorities wasted little time putting together a full-scale investigation of the incident. What they found was troubling to say the least: Not only was the mysterious Largemouth Bass Virus (LMBV) present in all of the dead fish found in Lake Fork, but it appeared that the virus had infected a number of other nearby Texas lakes as well.
“Every place we’ve looked, we’ve found it,” said Dr. Larry McKinney, Texas Parks and Wildlife senior director for aquatic resources, of the systematic intrusion of the virus in Texas lakes.
Investigation, research and frustration
After a thorough survey of Texas waterways, lakes, rivers and hatcheries, officials confirmed that the virus was present in Lake Conroe, Toledo Bend and Sam Rayburn as well. Also worrisome was the fact that the largemouth death toll on Lake Forks had climbed from approximately 50 fish in late June to over 4,000 fish in August of 1999.
With the Texas additions to the list of infected southern lakes – which by 1999 included Bay Springs, Tunica Cutoff, Columbus and Enid lakes in Mississippi as well as a handful of reservoirs in Alabama and Georgia – the urge to panic was great.
“The virus was really poorly understood at that point,” said David Terre, regional director for Inland Fisheries for the Texas Parks and Wildlife Department. “We really had to rely on our universities and scientists to help us figure out what was going on.”
As the news of the mysterious largemouth virus continued to spread, so, too, did the intrigue surrounding the disease. Throughout many of the southern infected waters, fishermen and scientists scrambled for answers. Where did the virus originate? Why did it continue to affect fish in predominantly southern waters? Were healthy bass populations in real jeopardy of being wiped out?
Although answers were slow to come, scientists began to see some definite patterns in the way the disease spread.
“What we observed at Lake Fork (in 1999) shows similarities to what happened at Sam Rayburn Reservoir,” said Terre. “Both die-offs occurred at the same time of year and the outward behavior of infected fish was the same. Dying fish at both lakes were observed struggling at the surface and had enlarged swim bladders. This is the clinical sign of LMBV.”
Compounding the problem was the fact that careful analysis of the LMBV was both time-consuming and costly.
“The testing is pretty complicated and costly. In fact, it costs us up to $150 per fish for a full dissection, full culture and Polymerase Chain Reaction (PCR) virus detection test,” said Terre. “Another problem is that we pretty much have to do the testing on dead fish. And in my opinion, we need to find a way to locate the virus without sacrificing fish. I think it would behoove the science community to develop some live testing measures.”
The conference
As the exhaustive research into the LMBV continued, scientists, marine biologists and other specialized environmental investigators throughout the south stepped up efforts to exchange information – an exercise that culminated in a highly publicized regional conference in Savannah, Georgia on Feb. 3, 2000. During the conference, attended by more than 70 environmental experts and scientists, attendees summarized their findings:
* Despite its mysterious origins, scientists concluded that LMBV is one of more than 100 naturally occurring viruses that affect fish but not warm-blooded animals. However, the true origin of the disease remains unknown.
* While the virus is related to those found in frogs and other amphibians, it has produced disease only in largemouth bass. Other species of fish have tested positive for the LMBV, however it only appears to be fatal in some largemouth bass populations. In addition, some healthy largemouth bass have tested positive for LMBV without showing signs of contracting the disease itself.
* LMBV attacks the swim bladder, causing bass to lose their capability to maintain buoyancy.
* Currently, the LMBV virus has been found in 12 states: Alabama, Arkansas, Florida, Georgia, Kentucky, Louisiana, Missouri, Mississippi, North Carolina, South Carolina, Tennessee and Texas.
* LMBV is not known to infect warm-blooded animals – consequently, it appears that humans don’t face any undue risk by coming into contact with infected fish.
While the conference was useful, scientists readily admitted that the disease continued to be poorly understood.
“The bad news is that we have a problem,” said McKinney. “The good news is that where this virus has occurred in the South, the impact has been short-term, and the fishery has quickly rebounded.”
The road to recovery and optimism
To be sure, the most positive news coming out of the scientific community is that the virus does not appear to be making a significant, long-term impact on healthy bass populations.
“We’ve tested all of the bass lakes in the state and we’re seeing a pretty good recovery in those lakes that were previously infected,” said Ron Garavelli, an officer with the Mississippi Department of Fisheries, Wildlife and Parks. “The bodies of water that had the problem are showing definite signs of recovery. We have seen some new infections this year. But we’re hoping that cycle (of disease) soon will be complete.”
Many environmental experts argue that the virus is following similar patterns of other related viruses typical to the outdoors.
“We see this with a lot of wildlife diseases,” said Garavelli of the perceived reduction of the virus and recovery of the infected bass populations. “There’s an initial impact and then gradually, the number of incidents decline. We were hoping this would happen in this case. And it appears that it has.”
Biologists liken LMBV to an outbreak of chicken pox among a class of school children. Once the infection is present, it spreads rapidly and can infect a large percentage of an isolated population. However, over a relatively short period of time, the disease begins to lose steam as resistance builds in the native habitat.
“I think what we’ve learned is that this virus is not the end of the world – it’s just another critter we have to deal with,” said Terre. “One thing we do know is that it doesn’t appear to be having any long-term effects on our fish populations.”
Like Mississippi, Texas lakes appear to have rebounded just as strongly.
“Lake Rayburn seems to be back in full swing,” said Terre. “We just caught seven lunkers on Lake Forks – so fishing is not dead.”
Back in Santee Cooper, things are looking up as well.
“On the last day of a recent fishing tournament on our lake, one angler landed 28 pounds of fish,” boasted Townes Walker, chair of the fishing committee for Clarendon County, S.C. “That goes to show you that the fish are still here.”
Which is good news for bass anglers everywhere. Not to mention the fish.