Vertebrate and invertebrate predation intensity on freshwater zooplankton communities

Abstract

PREDATION is widespread in the pelagic zone of lakes and both vertebrate and invertebrate predators are abundant and diverse in their feeding habits. Vertebrate predators are often size-selective and can virtually eliminate larger prey items1–3. These dramatic effects resulting from fish predation have led several workers to conclude that vertebrates contribute the largest percentage of the total predation intensity on freshwater zooplankton. Particular invertebrate predators, however, have also been shown to crop a substantial proportion of their prey populations4–6. I report here a study showing that invertebrate predation is more intense than vertebrate predation in the pelagic zone of Gull Lake, Michigan, with the first in situ evaluation of both types of predation on a single zooplankton prey assemblage. The significance of identifying major predation pathways in lakes is basic to many contemporary discussions of nutrient and energy flow as well as considerations of community structure and stability.