For the majority of bass fishermen, Largemouth Bass Virus (LMBV) is out of sight and out of mind, and has been for more than a decade.
But it's not out of our waters.
Is that reason for concern?
Yes. And no.
No, we aren't seeing numerous die-offs related to the virus that occurred for about a decade during the late 1990s and early years of this new century. And there's no reason to believe that's going to happen again. For example, it has not turned lethal in Saguaro Lake, where it was found in 2010. That discovery made Arizona the 19th state to detect the virus in its fisheries since 1991.
But it's still out there, and, yes, it still can kill, as evidenced by a die-off attributed to LMBV at a small Indiana fishery in 2012. It was the first documented in that state since 2001 at Hamilton Lake.
"Although the die-off was disappointing, it was not devastating," said biologist Neil Ledet, who accurately pointed out that nothing can be done to eradicate the virus."But we want to document where it causes fish kills," he added.
About the same time, resource managers reported finding the virus in four West Virginia fisheries.
Two years before, fisheries managers attributed LMBV as the cause for the decline in both catch rates and size of bass caught in Kerr Lake/Buggs Island on the Virginia-North Carolina border. “We’ve seen some declines in the growth rate, and it’s taking longer to catch a 5-pound fish,” biologist Dan Michaelson said. “But the big key has been the increase that we’ve seen in mortality. Since 2004, it’s up 10 percent, and that’s a lot.”
He added that testing also showed LMBV was present in bass in both the Roanoke/Stanton and James River drainages. "We're going to have to look around some more," he said.
More recently, biologists confirmed that northern snakeheads taken from two Potomac tributaries were infected with the virus. That might seem a good end for a bad fish that could cause the decline of bass and other native species.
But as we learned a decade ago, fatalities aren't always a foregone conclusion. In fact, the exotic fish simply could be carriers for spreading LMBV to bass throughout the Chesapeake Bay watershed.
Over the years, the virus has been found in other species as well, but, thus far, only in bass does it sometimes evolve into a fatal disease.
Why that is the case is one of many specifics that we still don't know about LMBV, including its origin, its means of movement from one water body to another, and why it proved fatal so often for about a decade, but since has leveled out to little more than a foot note--- albeit an intriguing one-- in fisheries management.
"The fisheries management community largely ignores it now," said Gene Gilliland, B.A.S.S. National Conservation Director. "It's not the threat it first seemed to be. It did not wipe out bass everywhere. And it's pretty species specific, unlike VHS, so it doesn't get much attention anymore."
By contrast, viral hemorrhagic septicemia virus has caused massive die-offs of several species, including bluegill, black crappie, drum, gizzard shad, and muskellunge, mostly in the Great Lakes. It also has been confirmed in smaller kills of smallmouth bass and walleye, and more than a dozen additional species have been identified as carriers.
VHS seems the most lethal in colder water, which is just the opposite for LMBV. Both are among more than 100 naturally occurring viruses that affect fish, but not warm-blooded animals.
"LMBV was suspected to be a new virus that evolved from a virus that infects amphibians, as I recall," Gilliland said. " Bass had no natural immunity to it so it spread quickly via who knows what means of transport. It has now runs its course in most places. Although it can be found in many populations, apparently immunities have built up and so far, the virus has not mutated enough to cause additional fish kills.
Still, we have educated guesses regarding the specifics of LMBV, thanks to annual seminars that B.A.S.S. convened until 2004. At those sessions, fisheries experts from around the country shared information and developed strategies for dealing with the outbreak. For example, they theorized that "stressed" bass seemed to be most susceptible and anglers likely aided in spreading the virus by moving fish and/or water in their livewells.
You can read about their findings and conclusions in a "fact sheet" posted at Bassmaster.com.