Presentation Type

Oral Presentation

Category

STEM (science, technology, engineering, mathematics)

Abstract/Artist Statement

Beaver-based restoration has shown to be an effective restoration strategy for turning incised streams into complex and dynamic systems. However, there are still uncertainties regarding the pros and cons of beaver and beaver dam analogs (BDAs) as it pertains to whole system effects. Concerns focus on whether these impoundments increase temperatures beyond thermal tolerances of cold-water species, reduce stream connectivity, and exacerbate negative effects of non-native species. In order to provide more context surrounding these concerns, we began a multiyear Before-After-Control-Impact (BACI) study on three pairs of streams (one restored with BDAs and one control) across Western Montana. In each stream, we measured changes in physical habitat (e.g., summertime water temperature, hydrologic residence time, instream habitat) and fish characteristics (e.g., movement, species composition). Thus far we have completed one season of pre-restoration (2019) and one season of post-restoration (2020) data collection. Generally, the effects of the restoration varied by site. For example, in one set of sites, there was evidence of an increase in residence time of water post-restoration leading to increased baseflows downstream of the BDAs. While we did not observe this effect in the other two restored streams. Additionally, we observed more variation in mean and maximum temperatures, as well as warmer temperatures, in the restored sites post-restoration compared with the controls. Even though we observed higher temperatures in the restored sites, this did not translate to increased temperatures downstream of the restoration reach. Here we present these and other preliminary findings from our field efforts.

Mentor Name

Lisa Eby

ALahr_GradCon.mp4 (73333 kB)

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Quantifying the effects of Beaver Dam Analogs on fish habitat and communities

Beaver-based restoration has shown to be an effective restoration strategy for turning incised streams into complex and dynamic systems. However, there are still uncertainties regarding the pros and cons of beaver and beaver dam analogs (BDAs) as it pertains to whole system effects. Concerns focus on whether these impoundments increase temperatures beyond thermal tolerances of cold-water species, reduce stream connectivity, and exacerbate negative effects of non-native species. In order to provide more context surrounding these concerns, we began a multiyear Before-After-Control-Impact (BACI) study on three pairs of streams (one restored with BDAs and one control) across Western Montana. In each stream, we measured changes in physical habitat (e.g., summertime water temperature, hydrologic residence time, instream habitat) and fish characteristics (e.g., movement, species composition). Thus far we have completed one season of pre-restoration (2019) and one season of post-restoration (2020) data collection. Generally, the effects of the restoration varied by site. For example, in one set of sites, there was evidence of an increase in residence time of water post-restoration leading to increased baseflows downstream of the BDAs. While we did not observe this effect in the other two restored streams. Additionally, we observed more variation in mean and maximum temperatures, as well as warmer temperatures, in the restored sites post-restoration compared with the controls. Even though we observed higher temperatures in the restored sites, this did not translate to increased temperatures downstream of the restoration reach. Here we present these and other preliminary findings from our field efforts.