Brook Trout Distribution, Genetics, and Population Characteristics in the Driftless Area of Minnesota

Abstract

The Driftless Area in southeastern Minnesota is on the southwestern edge of the native range of Brook Trout Salvelinus fontinalis. It was assumed that native Brook Trout were extirpated from this region in the early 1900s due to degraded stream conditions and stockings of eastern-origin Brook Trout and European Brown Trout Salmo trutta. Our objectives were to examine Brook Trout populations in the region to determine their spatial and genetic distribution and quantify population characteristics. Information on presence or absence of Brook Trout was gathered by electrofishing 174 streams in southeastern Minnesota. Brook Trout were present in 68% of coldwater streams compared with only in 3% in the early 1970s. The increase is likely due to increasing stream discharge throughout the Driftless Area, enabling recolonization or successful establishment of stocked populations. Streams with higher base flow discharge also had higher abundance, larger size at maturity, and larger Brook Trout present. Genetic data on 74 populations were analyzed to characterize genetic variation within populations, assess genetic structure among populations, and determine possible origins. Numerous populations were not associated with known hatchery sources but were primarily composed of geographic groupings that could represent remnant lineages. Although population characteristics were similar among genetic origins, potentially remnant populations should be given conservation priority because they have proven their ability to sustain themselves in this region. Management actions that emphasize maintaining or increasing stream base flows throughout the region will likely enhance remnant Brook Trout populations in the Driftless Area.

Received July 25, 2014; accepted March 17, 2015

ACKNOWLEDGMENTS

We would like to thank R. Bearbower, D. Casper, S. Erickson, S. Klotz, B. Lee, J. Magee, J. Melander, M. Peterson, J. Roloff, J. Schulz, V. Snook, and J. Weiss for their help in the field and J. Hennig, J. Jensen, S. Mackenthun, and S. Seim for their help in the laboratory. C. Anderson and three anonymous reviewers provided helpful reviews of this manuscript. This project was funded in part by the Federal Aid in Sport Fish Restoration Program (Project F-26-R).