Date of Award
Mark R. Luttenton
Carl R. Ruetz III
Global warming and conversion of forests for urbanization, agriculture and mineral extraction are increasing water temperatures throughout Brook Trout’s range causing population declines; particularly in populations persisting in marginal habitats and in the southern limits of their distribution. The Brook Trout is an ectotherm that can cope with elevated water temperature by moving to coldwater refuge such as groundwater seeps, coldwater tributary confluences, and headwaters. Availability of coldwater refuge is vital for the survival of Brook Trout populations threatened by increasing water temperatures. I used radio telemetry to study the movement, habitat use, and behavioral thermoregulation of Brook Trout living in Cedar Creek, a stream in southwest Michigan impacted by the deleterious effects of agriculture and urbanization on stream temperature. I evaluated Brook Trout thermoregulatory effectiveness during the summer when ambient water temperatures often exceed the ideal range for Brook Trout. My results helped direct management efforts aimed at restoring Brook Trout habitat in Cedar Creek. Overall, Brook Trout body temperatures conformed closely to ambient water temperatures. Brook Trout in a forested section maintained body temperatures within the ideal range for growth for most of the summer and occupied habitats characterized by large woody debris and overhanging vegetation. In a section routinely clear-cut and bordered by agriculture, Brook Trout body temperatures were often above proximate ambient water temperatures, and Brook Trout occupied deep microhabitats with little cover. Several Brook Trout emigrated from the clear-cut section into a forested section; however, most Brook Trout were largely sedentary. My results illustrate the importance of a forested riparian corridor in providing woody cover and thermal refuge in a marginal trout stream. Management efforts to restore Brook Trout habitat should prioritize evaluating target systems to identify limiting factors that provide important ecological benefits to threatened populations.
Wegner, Justin Emory, "Brook Trout Behavioral Thermoregulation and Habitat Selection in a Small Michigan Coldwater Stream: Implications for Successful Management" (2017). Masters Theses. 865.