Pre-Treatment Assessment of Habitat and Biota in the Knife River Mainstem, MN

Abstract

Pre-restoration surveys are important for demonstrating the effectiveness of restoration activities. Good documentation of stream condition, and the organisms that live there, allow post-restoration comparisons, assessment of the most cost-effective restoration activities, and the ability to track trends over time. During 2016 the Lake Superior Steelhead Association (LSSA) requested University of Minnesota Duluth, Natural Resources Research Institute (NRRI) staff to complete surveys of 3 Knife River mainstem reaches (two pre-treatment, and one reference) for fish, macroinvertebrates, and stream habitat. The 2016 Knife River surveys followed our standard methods used in past LSSA contracts. Reaches were named “Reach 12”, “Reach 9”, and “Reference” (listed in upstream progression). Reach 12 and Reach 9 were considered “pre-treatment” assessments, as habitat improvement projects to reduce stream bank erosion and improve pool and cover habitat for larger salmonids in these reaches occurred following our surveys. Data from the Reference reach will be important for distinguishing whether changes detected over time are natural or from the applied stream work. Our surveys revealed that all three reaches were quite similar in habitat, as well as macroinvertebrate and fish communities. Reach 9 had the most fish species due to one very large pool, but otherwise, was not very different from Reach 12. Reaches 12 and 9 had areas with unstable channel conditions and eroding banks, which were not present in the Reference reach. Therefore, the Reference reach ranked highest in the MPCA Stream Habitat Assessment (MSHA) protocol scoring system and percent canopy cover over the stream channel. The Reference reach also had more pools with slower-flowing water and woody debris, which Brook Trout favor. Thus, we found greater Brook Trout abundance and fitness in the Reference reach. In summary, our survey indicates all reaches were relatively similar. This assessment is important because it demonstrates the section of the river we selected for the Reference reach will adequately capture natural changes over time, while still being a comparable river segment to Reach 12 and 9.