Monitoring VHS Status of Illinois Lakes and Rivers and Movement of Fishes from Lake Michigan into Unaffected Waters

Over the past decade, viral hemorrhagic septicemia (VHS) has been detected in multiple locations throughout the Great Lakes region.  Hydrologic connectivity between Lake Michigan and the Illinois River drainage (via the Chicago Area Waterways (CAWS)) may increase the risk of VHS spreading into Illinois waters outside of the Great Lakes, in addition to the possibility of VHS range expansion to previously unaffected watersheds via wildlife- or human-mediated transport.  We have partnered with the Illinois Department of Natural Resources to conduct VHS surveillance in farmed and wild fish in Illinois since 2008.  Sampling locations have included 16 aquaculture facilities and 50 of 52 HUC-8 watersheds in the state, with additional focused sampling in the CAWS and harbors along the Lake Michigan shoreline.  VHS has been detected in spring samples from Lake Michigan harbors, but has not been observed in any other lakes, rivers, or canals in Illinois to date.  We have also estimated the frequency of movement of VHS-susceptible fish species from coastal Lake Michigan and its harbors into the CAWS, which link to the Illinois River drainage.  Results of these studies study will inform continued monitoring efforts and potential development of a watershed-based approach to VHS management in Illinois.