Density-Dependent and Independent Processes Regulating Brook Trout Populations within a Complex Riverscape: A Core - Periphery Approach

Metapopulation theory predicts that population densities should remain relatively high and stable in core habitats, whereas densities decrease and become more highly variable closer to the periphery. Brook trout in the Shavers Fork watershed, WV demonstrate such distributions, where core habitat is located in small tributaries and periphery habitat is located in larger mainstems. Using a 10 year data set, an information theoretic approach was used to test a series of candidate models that consider local and regional density dependent (DD) and density independent (DI) controls on brook trout population dynamics in core vs. periphery brook habitats. Our results indicate that DD mechanisms were the primary factor controlling population growth rates in both the core and periphery (6 of 7 sites), while young-of-the-year densities were influenced by recruitment limitation. Mobility in adults likely explained why regional DD models best described adult densities at most sites, and adult standard lengths were best explained by local DI factors. Autocorrelation analysis indicated stronger temporal synchrony among similar sized and closely spaced sites.  Our results support the hypothesis that brook trout population dynamics are controlled by density-dependent regulation within core habitats and dispersal processes at the watershed scale.