Great Lakes Prey Fish Populations: A Cross-Basin View of Status and Trends in 2006

O'Gorman, Robert; Gorman, Owen; Bunnell, David

Assessments of prey fishes in the Great Lakes have been conducted annually since the 1970s by the Great Lakes Science Center, sometimes assisted by partner agencies. Prey fish assessments differ among lakes in the proportion of a lake covered, seasonal timing, bottom trawl gear used, sampling design, and manner in which the trawl is towed (across or along bottom contours). Because each assessment is unique in one or more important aspect, a direct comparison of prey fish catches among lakes is problematic. All of the assessments, however, produce indices of abundance or biomass that can be standardized to facilitate comparisons of trends among lakes and to illustrate present status of the populations. Herein we present indices of abundance, standardized to the highest value for a time series within each lake, for important prey fishes in the various Great Lakes: lake herring (Coregonus artedi), bloater (C. hoyi), rainbow smelt (Osmerus mordax), and alewife (Alosa pseudoharengus). We also provide indices for round goby (Neogobius melanostomus), a new invasive fish presently spreading throughout the basin