Larval Fish Use of Dike Structures on a Navigable River

In rivers, velocity shelters are thought to serve as limiting factors in the retention and recruitment of young fish. Such shelters are formed in backwaters and tributaries; however, these areas are limited in many North American rivers. In response to this concern, several dike sites that serve as low-velocity zones were placed within the Kanawha River (West Virginia), a sixth-order tributary of the Ohio River. This study was conducted to evaluate whether the dike sites (finger and zipper dikes) provided velocity shelters that are used by larval fish. Larval fish were sampled during 2002 and 2003 using larval light traps. Larval fishes collected were typical of large river systems; Cyprinidae, Percidae, and Centrarchidae were the most abundant families. Results show that larval abundances peaked during late June in 2002 and early July in 2003. Overall taxonomic composition did not differ between dike sites and reference sites. Throughout the study, larval fish were captured at significantly higher rates (P < 0.001) at dike sites than at high- and low-quality reference areas. Water velocities were significantly lower (P < 0.001) at dike sites than at reference areas, suggesting that the greater larval fish use of dike sites may be attributed to reduced velocity provided by the structures. This study suggests that dike sites can serve as velocity shelters and retention areas for larval fish in navigationally impacted rivers.