A Linked Foraging and Bioenergetics Model for Southern Flounder

Abstract

Few predation models that simulate effects on prey survival and size structure also predict the corresponding effects on predator growth and size structure. To make this link, we parameterized a bioenergetics model for southern flounder Paralichthys lethostigma by conducting a series of respiration and feeding experiments as well as obtaining values from the literature. We then linked the bioenergetics model to an existing size-dependent foraging model for southern flounder feeding on spot Leiostomus xanthurus and tested it using data from a pond experiment. Integrating these two models allowed us to investigate the effects of size-dependent interactions on predator growth by making predator growth a function of size-dependent foraging success. The linked model predicts spot effects as well as the original foraging model does, but the accuracy of flounder growth predictions were size-dependent. Predictions of prey survival and size structure were robust and were not greatly affected by slight changes in predator foraging rates, but predictions of predator growth rate were very sensitive to slight changes in predicted foraging rates. This asymmetry in the linked model's predictive ability is derived from the nonlinearity of the prey length-mass relationship and the different currencies used by the foraging component (number of prey eaten) and the bioenergetics component (mass of prey eaten) of the linked model. Because bioenergetics model predictions of growth are inherently sensitive to estimates of food consumption, this asymmetry in ability to predict effects on prey numbers and predator growth will likely be a common feature of similarly linked models.