Rotifer abundance and composition in Lake Michigan: A significant data gap in understanding the potential for the establishment of Asian carp populations

Invasive silver and bighead carp (collectively referred to as Asian carp) have developed large populations in the Mississippi and Illinois rivers. There is a significant potential for the introduction of these invasive species to the Great Lakes through the Chicago Sanitary and Shipping Canal and other vectors. Recent assessments of phytoplankton and zooplankton abundance in Lake Michigan led to the general conclusion that only the most productive areas, such as Green Bay, river mouths, and large harbors, had sufficient food resources to support Asian carp growth. However, these studies only assessed the crustacean portion of zooplankton communities because accurate information on rotifer abundance was not available. Recent studies of Asian carp and zooplankton in the Mississippi River have shown that rotifers are an important prey item for Asian carp, and that mesh sizes typically used in zooplankton sampling (e.g., ≥63 μm) are too large to adequately assess rotifer abundance. We sampled the near-shore area of Lake Michigan using both a standard 63-μm mesh plankton net and whole water samples filtered through 20-μm mesh to accurately estimate the abundance of rotifers. With these data we will re-assess the ability of the Lake Michigan plankton community to support Asian carp.