Date of Award
Master of Science
Since the discovery of Viral Hemorrhagic Septicemia (VHS) in the Great Lakes in 2005, the assessment of its ability to spread amongst connected watersheds has been at the forefront of VHS management. This project was designed to determine a rate of passage of VHS-susceptible fish species between coastal Lake Michigan and its harbors and the artificial waterways in the Chicago metropolitan area. This information can be used to assess the potential for VHS to spread into the waterways, which drain into the Illinois River watershed. Although fishes (e.g. Round Goby and occasionally salmonids) are known to have moved from Lake Michigan into the Illinois River via the Chicago Area Waterway System (CAWS), the rate of fish passage from the lake into the waterway system is unclear. To directly assess fish movement, a total of 1216 fish were collected, tagged, and returned to Lake Michigan harbors (532, 43.8% of total) and Lake Calumet (684, 56.2%), an adjacent lake connected to Lake Michigan via the CAWS. Fishermen reports, Illinois Department of Natural Resources (IDNR) sampling, and subsequent electrofishing sampling trips yielded 51 recaptured fish (4.2% of tagged fish). Of these, 2 fish were recaptured below the O¡¯Brien Lock and Dam in the Calumet River (south of Lake Michigan and Lake Calumet) and 49 fish were recaptured in the location at which they were originally tagged. To further assess movement of VHS susceptible species between Lake Michigan and the CAWS, otoliths were collected from 375 small-bodied fish (<150 mm total length) captured in the CAWS and analyzed for ¥ä©ö©øC to determine the origin (Lake Michigan or CAWS) of these fish. Fifty-six percent of small-bodied fishes collected from the Calumet River were immigrants from Lake Michigan, whereas 35% of fish collected from the Chicago River and 28% of fish collected from the North Shore Channel were immigrants. Results indicate that fishes (particularly small-bodied species such as Round Goby) move between VHS-positive Lake Michigan into the VHS-negative Chicago area waterways and represent a potential vector for VHS to spread into the inland waters of Illinois. However, the lack of movement of fishes from Lake Michigan into the Des Plaines River and further downstream waters also indicates a watershed-based approach to managing VHS in Illinois waters rather than simply designating the entire state as VHS-affected due to positive samples in Lake Michigan, may be valid. VHS surveillance should be continued in the CAWS to ensure the status of these water bodies as ¡°VHS positive¡± or ¡°VHS negative¡± is accurate, as this is useful for informing the public and creating policies and regulations to attempt to slow the spread of this disease.
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