Viral Hemorrhagic Septicemia (VHS) is a deadly fish virus and invasive species that is threatening the current and future health of fish in Wisconsin.
VHS has been found in European freshwater trout since the 1930s and was first discovered in Great Lakes freshwater fish in 2005. It has caused massive fish die offs in Lake Huron, Lake Erie, Lake Ontario, Lake St. Claire, and the St. Lawrence River.
In Wisconsin, VHS was first detected in the Lake Michigan and Lake Winnebago systems in May 2007. In December 2009, lake herring collected from Lake Superior near the Apostle Islands tested positive for the VHS virus.
Scientists are not exactly sure how VHS arrived, although it appears the virus may have entered the Great Lakes through ballast water introductions, brought in frozen Pacific herring to be used as fishing bait, and by migrating fish from the Atlantic Coast. The virus can spread when infected fish discharge urine or reproductive fluids, and when healthy fish consume infected fish. In addition, the virus can survive in water for at least 14 days; increasing the probability of infecting more fish.
Symptoms of VHS include hemorrhaging (bleeding), bulging eyes, bloated abdomens, anemia, pale organs, unusual bleeding found in muscle tissue and internal organs, unusual behavior, rapidly deteriorating health, and death, although some infected fish may not show any symptoms at all. Fish that survive a VHS infection will develop antibodies to the virus, temporarily protecting it from future outbreaks.
VHS is one of the most serious fish pathogens because of its ability to kill in mass quantities, it affects a variety of fish species, and isn’t treatable. It is not a health threat to people who handle or consume their catch, but can have devastating effects to at least 28 fish species, including 19 sportfish!
Fish species that can be affected by VHS include black crappie, bluegill, bluntnose minnow, brown bullhead, brown trout, burbot, channel catfish, Chinook salmon, emerald shiner, freshwater drum, gizzard shad, lake whitefish, largemouth bass, muskellunge, shorthead redhorse, northern pike, pumpkinseed, rainbow trout, rock bass, round goby, silver redhorse, smallmouth bass, spottail shiner, trout-perch, walleye, white bass, white perch, and yellow perch.
Fish species have highly variable levels of susceptibility to VHS. Current research suggests that muskellunge are the most susceptible to death after coming in contact with VHS, followed by largemouth bass, yellow perch, rainbow trout, brook trout, brown trout, coho salmon, and Chinook salmon. Characteristically, cold water fish can tolerate higher doses of the VHS virus than warm water fish.
Like all aquatic invasive species in the Lake Superior basin, VHS is a serious threat to the waters of Wisconsin. A virus that is easily spread from fish to fish, doesn’t have a cure, attacks the immune system of fish with little to no resistance against the virus, and possesses the ability to harm at least 28 fish species is a deadly combination, literally.
Wisconsin boasts some of the most protective rules to prevent the spread of VHS and other aquatic invasive species among all of the Great Lakes states. We all need to follow the rules to ensure the spread of VHS is contained now and in the future.
Take these steps to ensure that your actions are not part of the problem, but the solution!
• Inspect your boat, trailer, and equipment.
• Remove any attached aquatic plants or animals.
• Drain all water from boats, motors, and equipment.
• Never move live fish away from a waterbody.
• Dispose of unwanted bait in the trash.
• Buy minnows from a Wisconsin bait dealer.
• You must drain all water from your boat and equipment when leaving any state water except: you can take up to 2 gallons of water needed to hold live minnows that can be legally transported as outlined below.
• You may not leave a water with any live fish, or fish eggs except:
• You can take live minnows bought from a Wisconsin bait dealer and left over after a fishing trip away from any state water and use them:
1) again on that same water, or
2) on other waters but only if no lake or river water, or other fish were added to the container.
This piece was written by Scott Caven, the aquatic invasive species (AIS) coordinator for the Ashland County Land and Water Conservation Department. For more information, please contact him at (715) 682-7187 or firstname.lastname@example.org.