Fish assemblage production estimates in Appalachian streams across a latitudinal and temperature gradient

Production of biomass is central to the ecology and sustainability of fish assemblages. The goal of this study was to empirically estimate and compare fish assemblage production, production-to-biomass (P/B) ratios and species composition for 25 second-to third-order streams spanning the Appalachian Mountains (from Vermont to North Carolina) that vary in their temperature regimes. Fish assemblage production estimates ranged from 0.15 to 6.79 g m(-2) year(-1), and P/B ratios ranged from 0.20 to 1.07. There were no significant differences in mean assemblage production across northern cold-water, southern cold-water and southern cool-water streams (p = .35). Two warm-water streams, not included in these comparisons, had the highest mean production and biomass values. Mean assemblage P/B was significantly higher in northern cold-water streams relative to southern cold-water and cool-water streams (p = .01). Species evenness in production declined with stream temperature and differed significantly across the lower latitude cold-water, cool-water and warm-water streams and the higher latitude (i.e. more northern) cold-water streams. Our fish assemblage production estimates and P/B ratios were both lower and higher compared to previously published estimates for similar stream habitats. This study provides empirical fish assemblage production estimates to inform future research on southern Appalachian streams and on the potential impacts of varying temperature regimes on cold-water, cool-water and warm-water fish production in the coming decades as climate change continues to threaten fish assemblages.