Contrasting Thermal Regimes and Winter Dynamics of Benthic Invertebrates in Trout Streams of SE Minnesota

Leonard Ferrington

Professor, Dept. of Entomology

Friday, November 4, 2016 - 3:00pm

The Driftless Region of southeast Minnesota has a diverse array of trout streams that are open for catch and release sport fishing during winter. Winter growth rates and survivorship patterns of brown trout are highly variable across streams, with low growth and high mortality in some streams, intermediate growth and mortality in most, and high growth rates combined with low mortality in a small number of streams. Contrasting thermal regimes among streams accounts for some of the variability, however food quality and prey density also likely contribute to brown trout growth and survivorship. Our research has shown that contrasting thermal regimes influence the types and abundances of wintergrowing and emerging aquatic insects used as food by brown trout in streams where growth rates are high and mortality is low. We have discovered that the winter growing and emerging aquatic insects have specialized life cycles, behaviors and physiological adaptations that enable them to survive at low temperatures. In this seminar I will review the life cycle dynamics and specialized adaptations that we have documented, and relate them to contrasting thermal regimes and trout growth.