Date of Award
Brook trout (Salvelinus fontinalis) are a cold water ectotherm whose native distribution includes most of eastern Canada, the upper Midwestern United States, and the eastern and mid- Atlantic United States as far south as Georgia. The native range of brook trout in the United States has been reduced as a result of interspecific interactions with introduced species, and anthropogenic land use changes that drive water temperature changes in many of their native watersheds. Anthropogenic land-use changes tend to increase thermal regimes of aquatic systems, affecting brook trout physiology and limiting them to colder, headwater reaches. The threat of thermal disturbance to brook trout distribution is most pertinent in systems that experience temperatures near 19°; the upper margin of the species’ optimal range. Cedar Creek, located in Kent Co. Michigan, contains a self-sustaining population of introduced brook trout and experiences temperatures >19°C during the summer. Cedar Creek presents a novel system to understand brook trout growth at the upper limits of their preferred temperature range, and predict how their growth may change under further thermal disturbance. I conducted a study to examine the foraging habits and growth of brook trout in Cedar Creek between June and August, 2015, and used a bioenergetics model to predict how brook trout growth would change if water temperatures were to increase during summer. Brook trout limited their activity during summer by remaining sedentary, and consumed energy dense terrestrial invertebrates, especially late in summer. But, the growth rate of trout that were recaptured was negative on average, and the bioenergetics model predicted that brook trout would lose body mass if the thermal regime of Cedar Creek were to warm. The major takeaway from this study is that riparian canopy, to cool the stream and promote terrestrial energy subsidies to brook trout diets, should be conserved in cool and coldwater streams. Although Cedar Creek is outside the native range of brook trout, I believe that this study has provided insight into brook trout growth, and the potential impact of increased water temperature on thermally-stressed populations.
Zaparzynski, Graeme R., "Evaluating Foraging Habits, and Estimating Prey Consumption, and Growth of Brook Trout in a Coolwater Michigan Stream" (2016). Masters Theses. 819.