The Ecology of the Zebra Mussel ( Dreissena polymorpha) in the Lower Great Lakes of North America: II. Total Production, Energy Allocation, and Reproductive Effort

Abstract

Five populations of Dreissena polymorpha from three lakes (Lake St. Clair, Lake Erie, and Lake Ontario) in the lower Great Lakes region were examined from 1992 through 1994 to determine the population dynamics, reproductive cycle, secondary production, and the allocation of resources to somatic tissue, shell, and gamete production. Secondary production, resource allocation, and reproductive effort are reported in this paper. Considerable temporal and spatial variation in secondary production was evident at both the population and the individual level. Differences in population production were attributed to population density, whereas variation in individual production was attributed to temperature, food supply, and the age structure of the population. Total production was broken down into its three components; somatic production, shell production, and gamete production. Analyses of the components showed that production within a site depended on the year examined, and that variation in total production depended on variation in somatic and shell production as gamete production was relatively constant in the populations examined. In response to poor environmental conditions, D. polymorpha shifts the allocation of resources from growth (somatic and shell) to reproduction. As individuals have no means of predicting how long adverse conditions will persist, investment in growth may be unprofitable.