Fish Behavior and Abundance At the Electric Dispersal Barrier in the Chicago Sanitary and Ship Canal, Illinois, USA

A series of electric barriers currently operate in the Chicago Sanitary and Ship Canal (CSSC) with a primary focus on preventing the upstream migration of bighead (Hypophthalmichthys nobilis) and silver carp (H. molitrix) into Lake Michigan. When our work began in the summer of 2011, Barrier II was operating at 2.0 V/2.54 cm. In November, 2011, barrier operating parameters were changed to 2.3 V/2.54 cm. Experimental work at the barrier consisted of pulling encaged gizzard shad (Dorosoma cepedianum) through the barrier and recording their behavior. Three weeks of caged-fish trials took place while barrier operating parameters were at 2.0 V/2.54 cm. Eight of 270 gizzard shad that were moved through the barrier were not incapacitated. After the barrier operating parameters were increased to 2.3 V/2.54 cm, seven additional weeks of caged-fish trials were performed and all fish were incapacitated. In addition, we conducted observational work that involved recording feral fish at 80 different fixed locations throughout the barrier system using a dual-frequency identification sonar (DIDSON). Review of our DIDSON footage revealed a significant accumulation of feral fish below the barrier and the highest numbers of fish in the summer and fall.