Muscle enzymes reveal walleye (Sander vitreus) are less active when larger prey (cisco,Coregonus artedi) are present

Abstract

Optimal foraging behaviour in walleye (Sander vitreus) was tested in eight lakes: four containing large prey (cisco, Coregonus artedi) and four without cisco. All eight lakes contained small prey (yellow perch, Perca flavescens). Activity costs and growth potential of walleye were estimated using white muscle enzymes. Anaerobic capacity, measured by lactate dehydrogenase (LDH), increased with walleye size and was lower in lakes with cisco. Aerobic capacity, measured by citrate synthase (CS), decreased with walleye size only in lakes without cisco. Growth potential of walleye, estimated by nucleoside diphosphokinase (NDPK), increased with size only in lakes with cisco. Overall, when cisco were available walleye were less active, able to maintain aerobic capacities, and increased their growth potential as they grew larger. Yellow perch LDH, CS, and NDPK were lower in lakes with cisco. This suggests that yellow perch were less active in lakes where walleye had an alternative large prey species, but yellow perch had higher growth potential when they were the only prey, reflecting the advantage of growth beyond edible sizes. This study reveals that there are physiological benefits for both predators and prey in communities with a wider range of prey sizes.