Leptodora kindtii Population Dynamics in the Island Region of Western Lake Erie before and after the Invasion of the Predacious Cladoceran Bythotrephes longimanus

Abstract

Competition among native and non-native species can cause decreases in population size and production of both species.  The native predaceous crustacean zooplankter Leptodora kindtii shares a similar niche with the invasive Bythotrephes longimanus in Lake Erie.  This niche overlap may contribute to the decline in abundance and production of Leptodora in the western basin of Lake Erie.  Historical (1946) and recent (2006) data were used to determine if the decline in Leptodora abundance and production was associated with the effects of Bythotrephes, which invaded Lake Erie in the mid-1980’s.  Pre-invasion abundances and lengths of L. kindtii were compared with current data (2006).  A change in prey community abundance, composition and dynamics were observed, relative to pre-invasion, with a marked decline in.abundance and size of L. kindtii after the invasion of Bythotrephes. Competition for food and direct predation are two explanations, among others, for the declines observed in L. kindtii size, abundance and production that have occurred since B. longimanus invasion.