Longitudinal Shifts in Fish Assemblage Structure Along a Non-Wadeable Iowa River

Non-wadeable rivers are unique and complex ecosystems that are highly susceptible to anthropogenic disturbance.  Despite the importance of non-wadeable river systems, little is known about the structure of fish assemblages in non-wadeable rivers, particularly in the midwestern U.S.  In 2001, the Iowa Wildlife Action Plan listed 68 fishes as Species of Greatest Conservation Need (SGCN).  Of the 68 SGCN, 35 typically inhabit large rivers.  The purpose of this study was to determine longitudinal structure of fish assemblages in the Cedar River, a large non-wadeable river in eastern Iowa, to better understand the distributions of fish SGCN and the potential influences from dams.  Fish and habitat data were collected from 13 reaches along the Cedar River.  A total of 16,630 fish were sampled representing 11 families, 70 species, and 18 fish SGCN.  Cluster analysis identified 3 major clusters of sampling reaches, each cluster exhibiting similar species composition.  The spatial orientation of clusters displayed shifts in fish assemblage composition along a longitudinal river gradient.