Midwest Fish & Wildlife Conference 2016

AUTHORS: Jamin G. Wieringa*, Central Michigan University; Andrew R. Mahon, Central Michigan University

ABSTRACT: Invasive grass carp Ctenopharyngodon idella were first introduced into the United States in 1963 as a biocontrol agent and have since been released or have escaped into multiple freshwater basins. While grass carp are bred as triploid and still distributed in some regions of the United States, multiple individuals, including reproductively viable individuals, have been previously captured in the Laurentian Great Lakes. While the overall extent of their impact is not fully known, grass carp pose a significant risk to native fisheries populations through their feeding on submerged aquatic vegetation that destroys food sources, shelter and spawning areas. With both diploids and triploids being repeatedly captured in the western basin of Lake Erie, the extent of the population that is reproductively viable has yet to be delineated. In this study, grass carp captured by commercial fishermen in Michigan waters of Lake Erie were sampled to determine the reproductive status of this population through collaborative efforts between our workgroup and the Michigan Department of Natural Resources. Between May 2014 and July 2015, a total of twenty-nine individuals were screened. Ploidy for each individual was determined by flow cytometry or visualization of nuclear morphology via microscopy. The resulting data are being used to determine the ploidy status of current populations within western Lake Erie. This work will enable management to understand the extent of the current invasion and determine means to manage population expansion.