¹Department of Biological Sciences, University of Windsor, Windsor, Ontario, Canada N9B 3P4
²Ontario Ministry of Natural Resources, Lake Erie Fisheries Station, Wheatley, Ontario, Canada N0P 2P0
³Sandusky Fisheries Research Unit, Division of Wildlife, Ohio Department of Natural Resources, Sandusky, Ohio, USA 44870
^**Present address: Ontario Ministry of Natural Resources, Glenora Fisheries Station, Picton, Ontario, Canada K0K 2T0

*Corresponding author: jeffrey.zhu@mnr.gov.on.ca

Summary

   We used a basin-wide bottom trawl dataset, collected annually from 1987 to 2003, to explore relationships between fish community composition and environmental variation in the western basin of Lake Erie. Over 1.6 million individuals representing 18 families, 38 genera, and 55 species were sampled from 1,253 effective trawls. Nine non-indigenous species (NIS) contributed >75% of the total abundance, dominated by white perch, Morone americana, (48.85%) and gizzard shad, Dorosoma cepedianum, (14.65%). Native yellow perch, Perca flavescens, was the next most abundant species, comprising 12.0% of the catch. Species richness did not vary appreciably within the time series, but catch-per-unit-effort (CPUE) was strongly influenced by NIS evenness and bathymetric attributes, which resulted in an increase in diversity indices (H’, D, J, PIE) of fish community through time. Multiple analyses of variance (MANOVA) identified significant interannual and depth-specific variation in water transparency, water temperature, and dissolved oxygen across the western basin. A canonical correspondence analysis (CCA) revealed a close association between clupeid abundance and environmental variation; the relationship was weaker for other soft-finned fish, and virtually absent for spiny-rayed fish. Three species-size groups were discriminated on the basis of feeding mode (planktivore vs. benthivore / omnivore) and thermal preference when the abundance of 18 important species was aligned with environmental gradients. Water transparency was the primary environmental gradient influencing community structure and may alter foraging effectiveness, both in terms of predator avoidance and prey detection. We conclude that synergistic effects of the invasion by dreissenid mussels and round goby invoked environmental fluctuations that altered predator-prey dynamics and thus the stability of fish community in western Lake Erie.