Comparisons of growth and condition of fluvial and resident brook trout within partially migratory populations

P>In partially migratory salmonid populations, growth and condition of migratory fish may be different than that of residents. To ascertain if a similar phenomenon exists in fluvial brook trout, Salvelinus fontinalis (Mitchell), populations, the growth and condition of fluvial and resident brook trout was measured in four Appalachian stream networks. Sites were sampled during summer, cohorts separated via scale analysis and differences in length and condition were investigated. Age-1 and -2 fluvial fish were significantly longer (P < 0.001) than residents of the same cohort. Additionally, age-2 fluvial fish had significantly greater condition (P < 0.005) than resident fish of the same cohort. This suggests that the use of spatially segregated resources can result in growth and condition advantages. However, potentially greater rates of mortality as suggested by low abundance in main stem sites may limit the fitness advantages of this energetically profitable, but ultimately risky, behaviour.