Linking fish habitat to their population dynamics

We classify habitat features based on their effects on fish population dynamics and how fish populations affect the habitat's dynamics. We term habitat features that can be reduced in quantity or quality by fish usage as consumable resources. In general, consumable resources regulate fish populations in a density-dependent manner. In contrast, nonconsumable habitat features influence fish populations in a density-independent manner. We further classify habitat features by the influence that fish have on the supply of that resource. We designate habitat features whose supply is unaffected by fish usage (e.g., space) as being dynamically unaffected. Thus, the supply of these resources does not depend on the present or past abundance of fish. The supply of dynamically affected habitat resources (e.g., prey abundance) depends on current and past fish abundance. Using lake whitefish (Coregonus clupeaformis), we illustrate how changes in fish habitat can be integrated with changes in fish growth, survival, and reproduction through a stock-recruitment relationship. This example shows that single measures of population response such as carrying capacity or changes in surplus production do not fully represent the population-level changes following a habitat alteration.