STOCHASTIC DYNAMICS AND DETERMINISTIC SKELETONS - POPULATION BEHAVIOROF DUNGENESS CRAB

Ecologists have fiercely debated for many decades whether populations are self-regulated by density-dependent biological mechanisms or are c ontrolled by exogenous environmental forces. Here, a stochastic mechan istic model is used to show that the interaction of these two forces c an explain observed large fluctuations in Dungeness crab (Cancer magis ter) numbers. Relatively small environmental perturbations interact wi th realistic nonlinear (density dependent) biological mechanisms, to p roduce dynamics that are similar to observations. This finding has imp lications throughout population biology, suggesting both that the stud y of deterministic density-dependent models is highly problematic and that stochastic models must include biologically relevant nonlinear me chanisms.