Mysid Life History and Seasonal Variation in Predation Pressure on Zooplankton

Abstract

The bivoltine life history of Neomysis mercedis in Lake Washington, Seattle, results in seasonal variation in population size structure that influences the amount and quality of predation suffered by its zooplankton prey. Population densities and size–frequency data for Neomysis are combined with information on the influence of body size on feeding rate and composition of the diet to predict relative predation intensity on five size classes of Daphnia over a 27-mo period. An imperfect relationship between mysid numbers and expected predation intensity and seasonal fluctuations in the relative vulnerability of different-sized prey are two consequences of the mysid's pattern of life history.