Foraging ecology of native pumpkinseed (Lepomis gibbosus) following the invasion of zebra mussels (Dreissena polymorpha)

Abstract

Invasive species are a major concern both biologically and economically because of the rates at which they spread and their alterations to ecosystems. Zebra mussels (Dreissena polymorpha) are of concern in many regions owing to expenses related to industrial equipment damage and control education efforts. However, their greatest cost may be their ecological impact across North America. We tested pumpkinseed (Lepomis gibbosus) from three populations in Ontario (Canada) to determine if there was variation across populations or sampling periods in the consumption of zebra mussels. Using a combination of stomach content and stable isotope analyses, we found that pumpkinseed diet consisted of primarily zebra mussels across all populations and sampling periods, including a minimum of 54% in all lakes and sampling periods based on stable isotope mixing models. The current resource use patterns of pumpkinseed in our study populations indicate that there has been a shift from their pre-invasion diet of benthic littoral invertebrates such as gastropods. The large-scale consumption of invasive mussels by native fishes may have important implications for natural biological control of these mussels, decreasing overall mussel abundance and rate of spread. We discuss our results in the context of their implications for the overall health and dynamics of aquatic ecosystems.