River Main Stem Conditions Influence Brook Trout Metapopulation Structure in Appalachian Watersheds

Central Appalachian brook trout have undergone extensive declines resulting in fragmented populations dominated by small, sedentary, short-lived trout. Here we summarize results from 14 years of research on a unique, well-mixed brook trout metapopulation inhabiting the upper Shavers Fork watershed in eastern West Virginia, USA.  Within this watershed, headwater streams serve as important spawning / source habitats that supply brook trout to larger downstream habitats.  Results from mark-recapture, genetics, and isotope studies suggest that main stem habitats are not simply sink habitats, but rather function as both supplemental foraging habitats and as dispersal corridors during cool years.  Bioenergetics modeling indicates that these functions are highly vulnerable to projected climate change, and loss of main stem function can be expected to fragment the watershed into a series isolated tributary subpopulations.  We hypothesize that warming in main stem habitats and barriers to dispersal between tributaries and main stems are at least partially responsible for the loss of large, mobile, long-lived brook trout in this region and that this effect is exacerbated by harvest and competition with exotic trout.  We propose a research initiative that would seek to identify and restore well-mixed brook trout metapopulations in central Appalachian watersheds.