Fish distribution, abundance, and behavioral interactions within a large electric dispersal barrier designed to prevent Asian carp movement

Abstract

We evaluated the abundance and behavior of wild fish within the electric barrier system in the Chicago Sanitary and Ship Canal. This electric barrier system serves to prevent the upstream migration of bighead carp (Hypophthalmichthys nobilis) and silver carp (Hypophthalmichthys molitrix) to Lake Michigan from the Illinois River. We found that fish were most abundant below the electric barrier during the summer and fall, were observed near areas of peak voltage, and sometimes persistently challenged the barrier. Fish were relatively scarce within the barrier system during the winter and spring. Fish that were able to penetrate the farthest into the barrier system were smaller and tended to aggregate at the water surface, near the canal walls. The accumulation of fish that we observed below the barrier, and the persistent challenging behavior, raises concerns about breaches any time the barrier is de-energized for maintenance or during intermittent power outages. Entrainment and breach caused by barges traversing the barrier are concerns as well because of the water movements they create and how they alter the electrical field.