Use of a Backwater Lake with Restored Lateral Hydrologic Connectivity By Invasive Bighead and Silver Carp

River degradation, floodplain disconnection, and expanding populations of non-native species have interacted to stress native fish communities in many river ecosystems.  Restoration of lateral hydrologic connectivity can mitigate some of these impacts.  Swan Lake, an Illinois River (USA) backwater lake, underwent habitat enhancements to maintain lateral connectivity and benefit native fishes although invasive fishes could also exploit such improvements.  Use of Swan Lake was observed for invasive bigheaded carp (Silver Carp, Hypophthalmichthys molitrix [Valenciennes] and Bighead Carp, H. nobilis [Richardson]) using acoustic telemetry.  Backwater use (passages in/out and residency) by bigheaded carp was highest in spring and positively associated with depth of the entrance channel.  Bighead Carp use was correlated with temperature-related variables, while Silver Carp use was correlated with water levels and discharge.  Maintenance of a shallow access channel into backwater habitats may limit their use by bigheaded carp.  Additionally, observed diel, temporal, and environmental relationships could be exploited to reduce bigheaded carp backwater use.