Dissertation Research: Demographic and Genetic Analysis of Metapopulation Dynamics: Emerita analoga as a Model Organism

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9902218Botsford, Diehl & Grosberg Many organisms are distributed as discrete subpopulations over space, interacting only when certain life stages move between them. However, we have a poor understanding of how migration rates and spatial structure of these metapopulations affect overall population dynamics, abundance, or stability. Populations of benthic invertebrates like lobsters and crabs are distributed along long stretches of coastline. They commonly do not move much as adults, but have a larval stage that can move about in ocean currents for thousands of kilometers. We have a poor idea of how far larvae move, how that varies with ocean conditions, and how these influence population dynamics. The sand crab, Emerita analoga, is a good model system because the adults and larvae are abundant and can easily be sampled without complicated or expensive gear. This crab is distributed along the west coast of North and South America. In this project genetic markers and field studies are being used to learn more about how ocean currents transport larvae among a number of adult populations along the coast from southern California to northern California, and how population dynamics are subsequently affected. Gaining a better understanding of the dynamics of populations along coastlines, interconnected by dispersing larvae has practical value in managing fisheries, predicting responses to pollution, and anticipating the effects of climate change. When managing such populations, one needs to know how reproduction at one location contributes to populations at another location, and how this affects population dynamics. For example, this study will provide understanding of how increasing harvests of American lobsters from some offshore populations affects the future of nearshore fisheries. It will also tell us how an oil spill in Oregon would affect the crab fisheries in California and Washington.