Driftless Area Brook Trout

Salvelinus fontinalis

The Driftless Area in the midwestern United States is a distinct landscape in the Upper Mississippi River Basin that was left unglaciated during the last glacial period ending 10,000 years ago. The term “driftless” indicates a lack of glacial drift, which are sediments left behind by glaciers. The area is characterized by karst topography, with springs, caves and sinkholes. Coldwater streams and rivers cut steep canyons prior to joining the Mississippi River. The Driftless Area encompasses southwestern Wisconsin, southeastern Minnesota, northeastern Iowa, and northwestern Illinois.

Driftless Area Map

The brook trout Salvelinus fontinalis is the only trout native to the Driftless Area, and it was abundant in many streams prior to the 1850s. By 1900, brook trout were eliminated from many streams because of overexploitation and habitat degradation. Stream habitats were largely impacted when much of the natural prairie and forests were cleared for agriculture, fuels, and lumber. The reductions of natural land cover increased soil erosion and resulted in more frequent and larger floods. Upland soil erosion and flooding caused sediments to fill valley bottoms, which led to streams becoming wider and less connected with groundwater. When combined with a reduction in riparian vegetation and wood recruitment into streams, the wide, warm, and shallow streams were largely unable to sustain brook trout populations.

Beginning in the 1930’s, efforts were made to improve farming practices and decrease soil erosion. In the second half of the 20th century, the U.S. Soil Conservation Service – today known as the Natural Resource Conservation Service – helped farmers implement conservation farming practices to reduce soil erosion and improve water quality. The Department’s of Natural Resources of Minnesota, Wisconsin, and Illinois have partnered with local governments and organizations, including Trout Unlimited, to improve trout habitat in Driftless Area streams. In the past these efforts were not coordinated on a broad scale, but today several efforts are being made to strategically coordinate restoration efforts across the region. The Driftless Area Initiative is a multi-state partnership of federal agencies, state agencies, private organizations, and private individuals designed to restore and enhance the Driftless Area’s ecology, economy, and cultural resources. The Driftless Area Restoration Effort is a Trout Unlimited effort aimed at restoring the coldwater streams and watersheds in the area.

Our CSI analysis incorporated data from the Wisconsin Department of Natural Resources, Minnesota Department of Natural Resources, Iowa Department of Natural Resources, Illinois Department of Natural Resources, and the Driftless Area Initiative. Their contributions were key to our understanding of brook trout in this area and development of the CSI. A complete list of data sources is provided at the bottom of the website.

Key CSI Findings

• Brook trout occupy variable amounts of their estimated historic range across the Driftless Area; however, their historic distribution in the Driftless Area is not precisely known
• Adult population densities are moderate, but many populations have limited extents
• The genetic purity of many populations is uncertain because of past stocking of eastern brook trout strains; however, current research is focused on understanding the genetic purity of populations across the Driftless Area
• Very little land across the Driftless Area has a formal protective status
• All but one subwatershed had Watershed Condition scores of 1 because much of the Driftless Area has been converted for agriculture, has a high soil erosion risk, and lacks an extensive forested riparian buffer
• Watershed connectivity in most subwatersheds has been disrupted by a high number of road crossings
• Water quality has been significantly impacted across the region due to an abundance of agricultural lands, high road densities along streams, and the presence of concentrated animal feeding operations. Many streams have been listed as ‘impaired’ during state water-quality assessments
• Dams and reservoir storage alter flow regimes in certain portions of the Driftless Area
• There is low risk of future land conversion because much of the landscape has already been converted for agriculture
• Only a few subwatersheds have high wind power development potential or have been identified for future hydropower development
• Increased stream temperatures due to climate warming pose a high future risk to stream habitats and brook trout populations across the Driftless Area
• Brown trout have been widely introduced and pose a risk to future brook trout restoration efforts

Prepared by Dan Dauwalter, 6/2009

Table 1. CSI scoring results for Driftless Area brook trout. Rangewide Conditions and Population Integrity indicators were scored only for currently occupied habitat (262 subwatersheds), while Habitat Integrity and Future Security indicators were scored for all 819 subwatersheds in the Driftless Area. All indicators are scored from 1 (poorest) to 5 (best): see detailed methods for scoring Driftless Area brook trout.

Conservation Strategies Map