Longitudinal and Lateral Patterns of Fish Species Composition and Biotic Integrity in the Lower Wolf River, Wisconsin, a Relatively Undegraded Floodplain River

Abstract

ABSTRACT The lower Wolf River, flowing 164 km from the Shawano Dam to Lake Poygan in east-central Wisconsin, is one of the least degraded large warmwater floodplain river reaches remaining in the United States. Seine and electrofishing samples were collected during 1997–2001 to characterize patterns of fish species composition and biotic integrity. Nearly 14,000 fish in 69 species were collected including the channel shiner Notropis wickliffi, which had not been reported before from the Great Lakes basin. Species distributions and multivariate measures of assemblage composition showed few consistent longitudinal patterns, but there were lateral differences between off-channel and main-channel habitats. Of the 40 most common species, 31 varied in abundance or distribution between main- and off-channel habitats, but only 10 species differed between upstream and downstream segments of the study reach. Index of biotic integrity scores based on main-channel fish assemblages indicated that the overall environmental quality of the study reach was good and that biotic integrity did not vary longitudinally. However, scores from survey sites with natural shorelines were significantly higher than scores from that included rock rip-rap.