Results of Pre-Treatment Habitat and Biota Surveys from the Knife River, MN Watershed

Abstract

This report follows the same layout and data summaries as the report provided to the Lake Superior Steelhead Association (LSSA) in 2017 (Dumke and Wellard-Kelly, 2017). Thus, much of the text from introduction and methods sections are repeated because each report has been written as a stand-alone document. The Natural Resources Research Institute (NRRI) was contracted in 2017 by LSSA to conduct pre-treatment stream habitat, fish, invertebrate, and water chemistry surveys on three segments of the Knife River mainstem anticipated to have channel restoration work applied in the future. The reaches were named ‘Reach 4.5,’ ‘Reach 4_ED,’ and ‘Reach 4_CB’ to match section labels used in planning by LSSA. We also measured all the same parameters in an upstream reach not expected to undergo any treatment, which serves as the control for later comparisons. This before-after-control-impact (BACI) design is our standard for attributing changes over time to specific treatments applied to the stream and is very useful in evaluating changes caused by habitat improvement projects. In total, four river segments (Reach 4.5, Reach 4_ED, Reach 4_CB, and Reference) were surveyed by NRRI with the full suite of options. In addition, three upper-watershed reaches (Mcarthy, Red Dot, and White Landing) were surveyed via electrofishing only with the goal of detecting age0 Rainbow Trout presence, and two reaches on the Knife River mainstem were surveyed with rapid-response thermometers to detect ground-water inputs which would be important trout refuge during hot summer periods.

We found that all reaches had water quality parameters acceptable for all salmonid species present in the Knife River watershed. In fact, we found a ground-water spring within one of temperature survey reaches. The pre-treatment reaches had lower MSHA habitat scores than the Reference, which was largely due to the presence of large eroding stream banks, but all reaches had fish habitat in the form of woody debris and pools. Brown Trout were present in the lower segments, but absent in upper watershed reaches. Brook Trout comprised more of the fish community as surveys progressed into the upper Knife River watershed, which is typical. Rainbow Trout were present in every electrofished river section, but only one age0 Rainbow Trout was collected within White Landing, and no age0 were detected in Red Dot. Red Dot and White Landing were not far apart, and the low capture of age0 Rainbow Trout indicates there was very little spawning activity, or poor spawning success, of Rainbow Trout in these upper sections during spring 2017. Macroinvertebrate communities were similar among the four reaches sampled for bugs, but the Reference had slightly fewer sensitive taxa, likely due to that reach being a steeper slope and dominated by larger boulders that were half-buried in the stream bed by smaller rocks (which offers fewer spaces between rocks for invertebrates to hide).