Lateral Movement and Use of Floodplain Habitat by Fishes of the Kankakee River, Illinois

Fishes were trapped moving between the river channel and two distinct floodplain habitats: an ephemeral ditch and a permanent pool. Twenty-five fish species were sampled by one-way traps and seine; dominant species were grass pickerel (Esox americanus), green sunfish (Lepomis cyanellus), pirate perch (Aphredoderus sayanus) and orange spotted sunfish (L. humilis). Numbers of fish trapped per day were positively correlated with river discharge yielding a significant exponential relationship. Recaptures of marked fish were rare indicating seasonal use of the floodplain. Juveniles made up 54.7% of the fish collected, revealing the value of floodplains as nursery areas. No significant migration trends of size or taxon occurred by date or discharge. Samples of fish leaving the ephemeral ditch and samples of those entering the permanent pool showed the highest similarity index value. These data suggest that flood exploitative fishes, those species adapted to flooding, continue to see favourable backwater habitat when forced off the floodplain.