Density-dependent individual growth and size dynamics of central Appalachian brook trout (Salvelinus fontinalis)

Density-dependent aggression, emigration, mortality, and individual growth have been identified in wild lotic salmonid populations. However, most work is limited to fish in the genus Salmo, and few studies consider density dependency coupled with observations of energy acquisition. We attempt to quantify density-dependent growth, size, and energy acquisition for a population of brook trout (Salvelinus fontinalis) in Appalachia, where the species is food-limited and population densities are low. Brook trout populations were intensely monitored over the course of 2 years at several sites within a watershed in eastern West Virginia. Tagging provided specific growth estimates, and diet analyses allowed for estimation of energy acquisition relative to maintenance requirements for adult fish. Young-of-the-year (YOY) brook trout exhibited density-dependent size relationships, but the intensity of density dependency varied substantially among months, with progressively decreasing slopes. Adult individual growth and excess energy acquisition was density-dependent, but only during periods when temperatures were warm and energy intake was low. The strong influence of temporal variability in density dependence of YOY size, as well as adult fish size, individual growth, and energy acquisition, suggests that density dependency in Appalachian brook trout may be driven by periodic prey resource scarcity.