Demographics and seasonal abundance of sportfish in three thermal habitats of Coffeen Lake

Abstract

Power generating facilities across Illinois provide electricity to residents of the state, while at the same time offering desirable open water fishing lakes that can be used by anglers during the winter season when other reservoirs are not accessible. Coffeen Lake represents one of the best power cooling fisheries in the state and boasts both excellent largemouth bass and channel catfish populations. The reservoir supplies water to a power station with a generating capacity of 945 megawatts of electricity, with 73% of the surface water affected by heated discharge and a cooling loop covering 4.1 miles. Sampling sport fish species in power cooling reservoirs such as Coffeen Lake presents challenges throughout the year due to fluctuation in temperatures and movement of fish throughout the lake; additionally, a recent rule change by the State of Illinois allows increased thermal loading during May and October to this reservoir. I used AC electrofishing to assess the current sportfish population of Coffeen Lake, and to examine differences in sportfish abundance among three thermal environments within the lake. In addition to AC electrofishing, pulsed DC electrofishing, and modified fyke nets were used to sample this assemblage and for gear comparison. I found AC electrofishing sampled a greater number of fish per hour of electro fishing, and AC electro fishing more effectively sampled sunfishes and channel catfish in Coffeen Lake. Pulsed DC electrofishing, using the Long Term Research Monitoring Program protocol, more effectively sampled largemouth bass. I found largemouth bass to be abundant and in excellent condition in Coffeen Lake. Distribution and abundance of largemouth bass was found to be influenced by thermal effluent, with bass concentration shifting to cooler waters during the fall and summer and into warmer habitats during winter. Crappie species, though in excellent condition, were low in abundance, especially in areas impacted by heated effluent. Channel catfish were found to be in average condition; greater densities of channel catfish were found in the cooling loop of Coffeen Lake during the majority of the year. Overall, spring sampling resulted in more consistent distributions of sportfish, especially largemouth bass, most likely due to relatively cooler water temperatures throughout Coffeen Lake during the early part of the year.

Date of Award	2012
Original language	American English
Awarding Institution	Eastern Illinois University
Supervisor	Robert E. Colombo II (Supervisor)