Equation-free mechanistic ecosystem forecasting using empirical dynamic modeling.

It is well known that current equilibrium-based models fall short as predictive descriptions of natural ecosystems, and particularly of fisheries systems that exhibit nonlinear dynamics. For example, model parameters assumed to be fixed constants may actually vary in time, models may fit well to existing data but lack out-of-sample predictive skill, and key driving variables may be misidentified due to transient (mirage) correlations that are common in nonlinear systems. With these frailties, it is somewhat surprising that static equilibrium models continue to be widely used.

Prey selection by an intertidal beetle: field test of an optimal diet model.

Adult beetles Thinopinus pictus LeConte (Staphlyinidae) live on sand beaches in temporary burrows from which they emerge at night to prey on amphipods Orchestoidea calforniana (Brandt). I constructed models of amphipod size selection by beetles, using the size distributions of amphipods measured on the beach, and the results of laboratory experiments on capture success, reaction distance and feeding rates. Capture success decreased and the probability that an amphipod was detected increased with increasing amphipod size.