Prey selection by larval northern pike (Esox lucius) exposed to different zooplankton assemblages representing seasonally flooded wetland and nearshore bay habitats

Abstract

A prey selection experiment was designed to investigate whether northern pike larvae, at swim-up and advanced stages, select similar zooplankton prey in seasonally flooded wetlands and nearshore littoral zones, which represent primary St. Lawrence River northern pike spawning habitats. At first exogenous feeding, naïve swim-up larvae exposed to both wetland and nearshore zooplankton were generalist consumers, feeding primarily on cyclopoid copepods and small cladocerans. No positive selection was observed for any prey taxa. Advanced larvae began to exhibit positive selection for large cladocerans. Significantly larger-sized prey were consumed by advanced larvae given wetland vs. nearshore zooplankton. Large cladocerans made up a greater proportion of the assemblage originating from seasonally flooded wetlands vs. nearshore habitats, and may explain the difference in size selectivity. Our laboratory experiment suggests pike hatched in wetland environments have greater access to preferred, large cladoceran prey, and differences in spatial and temporal spawning distributions may have important implications for zooplankton availability and hence food consumption during the critical larval period.