Effects of habitat enhancement on 0‐group fishes in a lowland river

Loss of habitat complexity through river channelization can have adverse affects on riverine fauna and flora through reductions in abundance and diversity of species. Habitat enhancement schemes are used to improve the physical and biological heterogeneity of riverine habitats. Between 1996 and 1997 the Environment Agency undertook a habitat enhancement scheme on the Huntspill River, Somerset, England to improve conditions for coarse (non-salmonid) fishes. The scheme involved reducing bank gradients and the construction of off-channel bays in parts of the channel, all of which were planted with willow (Salix sp.) and common reed (Phragmites australis). The effectiveness of the enhancement scheme was investigated by comparing 0-group fish assemblages in manipulated and unmanipulated sites. Abundance and diversity of 0-group fishes was significantly higher in manipulated habitats. There was no significant difference detected in the effects of the different types of enhancement measure used. The significance of microhabitats produced by habitat enhancement schemes is discussed with respect to spawning, nursery and refuge sites for 0-group coarse fish assemblages. Copyright © 2001 John Wiley & Sons, Ltd.