Limnetic feeding behavior of juvenile sockeye salmon in Lake Washington and predator avoidance 1

Abstract

Patterns of limnetic feeding behavior (vertical movement, schooling, diel feeding chronology, zooplankton prey selectivity) of Lake Washington juvenile sockeye salmon are described. A general hypothesis to explain the relative fitness of alternative behaviorial decisions is presented. The limnetic feeding behavior of the salmon appears to minimize their vulnerability to predation by the visual piscivore, northern squawfish. Seasonal variation indicates that sockeye feeding behavior is a short term optimization process involving foraging success and encounters with northern squawfish. Lake Washington sockeye salmon can afford to spend a large amount of their time engaged in antipredator behavior at the expense of foraging success because Lake Washington is comparatively zooplankton‐rich and the energy demands of the fish can be met in short foraging periods. Sockeye in other less productive systems show a more aggressive exploitation of the zooplankton.