Spatial and temporal drivers of variability in abundance of two stream fishes

Abstract An understanding of how and why animal populations vary in space and time informs effective conservation and management. We used spatial and temporal flow metrics to explore flow-ecology relationships for two fish species, Mountain Sucker Pantosteus platyrhynchus (Cope, 1874) and Mottled Sculpin Cottus bairdii Girard, 1850, across 64 sites and 8 years in Wyoming, U.S.A. We found variation in Mottled Sculpin and Mountain Sucker abundance was driven to a greater extent by spatial flow metrics (e.g., drainage area, median summer flow) with differing direction of response between species. The opposing responses to spatial variation in median summer flow could reflect the ability of Mountain Sucker to persist in non-perennial habitats, likely due to their relatively high mobility and recolonization capacity. Responses to temporal flow metrics (e.g., previous year spring flow, previous year autumn flow) were weaker but consistent across species likely due to similar reproductive strategies and timing. The lack of stronger flow effects on population variability in both species likely corresponds to high variability in local habitat characteristics that are mediating population response. These findings underscore how considering spatial context informs conservation planning and suggest that flow-ecology relationships may be mediated by species-specific traits and local habitat conditions.