Chapter 13 - Simulating Large-Scale Population Dynamics Using Small-Scale Data

Abstract

This chapter addresses various issues related to population ecology of coral reef fishes, such as the influence of density-dependent interactions among reef fishes on fluctuations in their abundance, the types of density-dependent interactions among reef fishes that result in their population regulation, and the influence of density-dependent interactions at small scales on population dynamics at larger scales. Field manipulations are viewed as the best way to detect density dependent interactions, to identify the stage in the life cycle at which they occur, and to isolate their biological causes. Regulation occurs when density dependence has a direct effect that is strong enough to put bounds on temporal fluctuations in abundance, but not as strong or delayed in its effect to have a destabilizing effect on abundance. Variation in demographic rates that is unrelated to density can have major effects on population dynamics, but can never regulate populations. The model presented in this chapter predicts that density-dependent interactions occurring among groups of fishes that occupy small patches of reef, a few meters across, are not irrelevant when the field of vision is expanded to vast areas. The model also indicates that the quantitative influences of local density dependence on mesopopulation abundance were strongly conditional on which demographic rates were functions of density. The model results also predict that changes in the overall rate at which adult fishes move among reefs should not cause qualitative changes in mesopopulation dynamics.