Habitat and Fish Community Response to Sand Dredging in a Large Great Plains River

In-stream sand dredging removes sediment from localized areas within the river channel and disrupts sediment transport, potentially altering aquatic habitat.  We investigated the role these potential habitat alterations play in the structure of fish communities and habitat availability within the Kansas River, a large sand-bed river.  Fish were collected monthly from June to November 2010 from eight, 1 km reaches in Edwardsville, KS (two actively dredged, one historically dredged that have not been dredged in at least one month, and five control reaches) and five 1 km reaches in Lawrence, KS (one actively dredged, one historically dredged, and three control reaches) with bottom trawls, seines, and electrofishing.  Water depths and velocities were measured with an Acoustic Doppler Current Profiler in all reaches.  An ANCOVA was used to determine if water depth, velocity, or fish habitat guilds catch per unit effort (CPUE) differed among reach types (actively dredged, historically dredged, and control), accounting for sampling month.  Water depths were approximately 1 m deeper in actively dredged reaches than in control reaches at one location (Lawrence; p=0.016), but this pattern was not evident at the other location (Edwardsville; p=0.158); mean water velocity did not differ among reach types for each location (p>0.183).  Only four of the 30 fish guilds analyzed showed any differences in CPUE among reach types.  Large bodied native fluvial dependents (collected by electrofishing at the Lawrence location) had higher CPUE in historically dredged reaches than in control reaches (p=0.050), but fluvial specialists collected by electrofishing had higher CPUE in control reaches than in dredged reaches (p=0.003).  Small bodied native fluvial dependents and non-native generalists (collected by seining at the Edwardsville location) had higher CPUE in historically dredged reaches than in control reaches (p=0.002), but non-native generalists had higher CPUE in dredged reaches than in control reaches (p=0.012).  Species in need of conservation (blue sucker, shoal chub, and johnny darter) were present in all reach types.  Our results suggest that instream sand dredging in large Midwestern rivers may alter water depths, but substantial changes in native fishes at dredge sites was not evident.