Trout Streams Assessment

Project Details by Fiscal Year
2011 Fiscal Year Funding Amount
Fund Source
Environment & Natural Resources Trust Fund
U of MN
Recipient Type
Public College/University
Start Date
July 2010
End Date
June 2013
Counties Affected
Project Overview

Trout require streams with excellent water quality that are fed by groundwaters that keep streams cold in summer but ice-free in winter. Minnesota has more than 680 designated trout streams that represent a valuable natural resource having high economic, sport, and habitat importance. However, over the long term this resource is under threat from climate change, which will likely increase stream temperatures and could detrimentally impact trout behavior, reproduction success, and food sources, particularly the cold-adapted aquatic insects that are essential in winter diets of trout. This appropriation is enabling University of Minnesota's Department of Entomology to study the health of trout streams in southeastern Minnesota and how changes in stream temperatures could impact the diets and growth of trout populations.

Trout streams in southeastern Minnesota differ markedly in brown trout abundance and growth during winter. Our project objectives were to better understand stream thermal regimes, fish feeding, and fish growth patterns between November and March, so habitat management strategies can be designed to maximize trout production. Prior to this study there was very little detailed knowledge of the winter diets of trout, and virtually no knowledge of the kinds and quantitative abundances of aquatic insects growing during winter. To achieve project objectives, we assessed trout lengths and mass two or three times per winter in 36 streams (12 streams/year for three years) and determined the types of aquatic invertebrates eaten by the trout, the abundances of these dietary organisms in the streams, and the corresponding patterns of trout growth. Our findings show trout are most abundant in streams where groundwater (springs and seeps) inputs keep water temperatures significantly warmer and ice-free in winter. These thermal conditions promote high abundance or emergence of aquatic insects specifically adapted for emergence and reproduction in winter, even when air temperatures are substantially below freezing. Some species that we discovered have never been described and are new to science. We developed predictive models relating air temperatures to water temperatures in areas buffered by groundwater. The models also demonstrate linkages between groundwater input and (1) the corresponding aquatic insect composition and their abundances, (2) the trout diets during winter and (3) trout growth patterns as a function of types of aquatic insects eaten. Based on our predictive models we are able to recommend conditions under which in-stream habitat management efforts can be better spatially focused to maximize trout growth and abundance. This information is being communicated to Trout Unlimited and the MN Department of Natural Resources to help inform their programs to manage trout streams.

Our results have been presented at local, state, regional, national and international scientific meetings and at local and state conservation planning sessions. Staff of the MN DNR assisted with much of our field work and have participated in interpreting and writing summaries and drafts of manuscripts for peer review. Consequently, they are very familiar with our findings. In addition, we are communicating our results to regional Trout Unlimited members, and hope to be able to discuss how our findings can help guide the in-stream habitat improvement programs. Two theses have been completed, and three additional graduate students will use portions of our findings as sections for their Ph.D. dissertations. One undergraduate worked on a class activity in Spanish to help serve as an "in-reach" effort to inform undergraduates in areas such as humanities and arts of our research. One newspaper article was written, and we have put videos of our field work on-line for public viewing via our Facebook sites.

Project Publication:
Winter feeding, growth and condition of brown trout Salmo trutta in a groundwater dominated stream

Project Details
Legal Citation / Subdivision
M.L. 2010, Chp. 362, Sec. 2, Subd. 05i
Appropriation Language

$300,000 is from the trust fund to the Board of Regents of the University of Minnesota to assess cold water aquatic insect abundance related to warming water temperatures as predictors of trout growth in southeastern Minnesota and assess options to minimize stream temperature changes. This appropriation is available until June 30, 2013, by which time the project must be completed and final products delivered.

2011 Fiscal Year Funding Amount
Proposed Measurable Outcome(s)

Click on "Final Report" under "Project Details".

Measurable Outcome(s)

Click on "Final Report" under "Project Details".

Project Manager
First Name
Last Name
Organization Name
U of MN
Street Address
219 Hodson Hall, 1980 Folwell Ave
St. Paul
Zip Code
(612) 624-3265
Administered By
Administered by