Netting crews check their nets for broodstock on the Mississippi River. - FWS photo

LaCrosse Fish Health Center Biologist necropsying wild fish from Pool 9. - FWS photo

Concerns over a new strain of fish virus that is causing widespread fish die-offs in the Great Lakes has caused fisheries managers to alter many ongoing management programs this year.  

VHS, or Viral Hemorrhagic Septicemia, is a serious fish virus that causes hemorrhaging of skin, muscle, and internal organs, with death following. There are concerns that fish movements from the Great Lakes and interconnected waterways may lead to the unintentional spread of the virus. 

Due to these concerns, the United States Department of Agricultures Animal and Plant Health Inspection Service (APHIS) passed an emergency rule that stopped all interstate movement of fish from the Great Lakes states until fish were tested for the virus.  To further protect inland fisheries populations, some states have decided to further regulate fish movement. 

In early April, the state of Wisconsin shut down all transfer of fish from the Great Lakes and the Mississippi River to instate waters in hopes to isolate inland waters from the virus.  Genoa has operated wild broodstock and egg collections from the Mississippi River since its inception in 1932.  

Due to this state emergency order, none of the northern pike egg and fry requests for inland waters of the state were able to be filled.  Fishery managers use northern pike as a top of the food chain predator in systems where rough fish control is needed.  Some non-native species such as common carp can cause declines in water quality due to the fish’s habit of stirring up bottom sediments, as well as altering habitat by uprooting or consuming aquatic vegetation.  

The Horicon National Wildlife Refuge has used this management tool in an attempt to control carp populations since the early 1990's.  Due to the state emergency order, which occurred after pike egg collections had already commenced, a total of just under 1 million northern pike fry were returned to Pool 9 in the Mississippi River, their place of origin. 

Wild fish health surveys on Pool 9 have been occurring since 1997, with many species of fish being tested for a wide range of pathogens including VHS.  No incidence of the virus has been detected as of yet. 

Regional fisheries personnel, including the LaCrosse Fish Health Center, will continue to monitor the Upper Mississippi River in an effort to track this and other fish health threats through the National Wild Fish Health Survey.