Fish assemblages and barriers in an urban stream network

Abstract

AbstractStream networks are vulnerable to fragmentation. Anthropogenic structures, such as dams and culverts, can isolate stream branches, potentially interrupting longitudinal gradients of fish distribution. The effect of single barriers is well documented, but the effect of multiple barriers in small streams is not as well characterized. We used a landscape approach and spatially continuous sampling across 2 y to examine the influence of anthropogenic structures on fish distributions in an urban stream network. After accounting for spatial autocorrelation, we found higher Coastal Cutthroat Trout (Oncorhynchus clarki clarki) and lower Prickly Sculpin (Cottus asper) densities at locations up- than downstream of multiple culverts. Culverts had species- and year-specific stepwise effects that overrode fish distribution patterns attributable to environmental gradients. Prickly Sculpin exhibited strong spatial autocorrelation in both years, whereas Coho Salmon (Oncorhynchus kisutch) had negligible spatial aut...