This is the first confirmation of the virus in Minnesota and Wisconsin waters. Pool 3 is located in a stretch of the river between Hastings and Red Wing, both in Minnesota, and Pool 7 stretches from Trempealeau to just north of LaCrosse, both in Wisconsin.
The virus was found in smallmouth bass taken from Pool 3, as well as white bass, rock bass, largemouth and smallmouth bass in Pool 7. Fish samples tested from Pools 4 and 9 show no sign of the virus to date, and none of the fish show signs of disease. The Service and its partners will continue routine monitoring of fish health in future surveys.
"Were still in the early stages of determining what this virus means to the bass populations in the Mississippi River," Rick Nelson, Fish Health Center project leader, said. "But we are continuing our work with the states to monitor for its impact."
The Fish Health Center staff and its partners identified presence of the virus while performing annual fish health sampling for the National Wild Fish Health Survey. The survey began in 1997 and identifies disease in wild fish and monitors its distribution throughout the country.
Its currently unknown how prevalent this virus is in wild populations, or the effect the virus has on bass populations. Extensive testing has only begun within the last few years and more study is required to determine range and effects in wild populations.
Nelson said, "Largemouth bass virus is one of more than 100 naturally occurring viruses that affect fish, but not warm-blooded animals. The virus was first identified in 1995 from a South Carolina reservoir with a large number of fish that had died. Biologists linked the fish kill to the largemouth bass virus and have since located this virus in 17 states, including Illinois, Indiana, and Michigan in the Midwest,
