The relationship between piscivory and growth of white sucker (Catostomus commersoni) and yellow perch (Perca flavescens) in headwater lakes of the Canadian Shield

We used data from a survey of 36 headwater lakes of the Canadian Shield to investigate the relationship between piscivory and growth, abundance, and longevity of white sucker (Catostomus commersoni) and yellow perch (Perca flavescens). The occurrence of northern pike (Esox lucius) and walleye (Sander vitreus) explained variations in the abundance of both white sucker and yellow perch, suggesting strong predation-induced mortality. The longevity of both species tended to be negatively related to increased piscivory. White sucker grew better and had a better condition in lakes with piscivores. Yellow perch showed only small among-lake differences in growth and condition. The superior competitive ability of white sucker over yellow perch could explain why yellow perch did not show improved growth or longevity where population densities were low in lakes with piscivores and white sucker. Furthermore, yellow perch growth was inversely related to the biomass of piscivorous fish in their first year of life. Stomach content data suggest that small yellow perch, which rely on zooplankton, might restrict their use of pelagic resources to reduce their predation risk by piscivores, thus reducing their growth. Our results show that the effects of piscivores can be species- specific and dependent on community structure.