On August 1 members of the La Crosse Fish Health Center and the La Crosse Fisheries Resource Office completed an annual fish health assessment.  The assessment took place on pool 4 of the Mississippi River near Lake City Minnesota.  Annual assessments are a useful tool for biologists to track the health history of a fishery. Health assessments have taken place on pool 3 since 1999.  A total of 158 fish from14 species were sampled for fish pathogens. 

The fish health center screens for all certifiable fish pathogens, but there are three viruses which sampling has focused on.  They include Viral Hemorrhagic Septicemia Virus (VHS), Spring Viremia of Carp Virus (SVCV), and Large Mouth Bass Virus (LMBV).  These viruses have a significant impact on fish populations.

Recently VHS has become a virus of great concern.  This virus was first discovered in 2003 in Region 3.  At this time, VHS has been isolated from 25 different species in Region 3.  The virus causes bleeding in the muscles, skin, and internal organs.  Other signs that the fish may be sick are pop-eye, fluid in the body cavity, and necrotic organs.  The virus has been found in four of the five Great Lakes.  To date, Lake Superior has remained free of the virus.

SVCV is also a virus of concern; it is classified as an exotic virus.  In the spring of 2002, Spring Viremia of Carp (SVC) was discovered in North Carolina and Wisconsin; these were the first documented cases of SVC in the United States.  Recently SVC was isolated in Pool 8 of the Mississippi River below Dresbach Dam.  The fish health center is trying to determine its distribution through the region.

Another virus of concern is LMBV.  This virus affects Largemouth Bass, but members of the sunfish, temperate bass, and walleye families can be carriers of the virus as well.  The virus causes lesions, yellow/waxy swim bladder, and fluid in the body cavity.  LMBV has been found on the river, but its prevalence is still being researched.