Quantitative Food Web Analysis to Detangle Restoration Effectiveness in Co-limited Habitats

Year: 2020
Presenter/s: John Jorgensen
Symposium Session: 2020 - 05 Assessing biotic response to environmental change
Topics covered: amphibians, beavers, fish-cutthroat, fish-salmon, fish-steelhead, monitoring, riparian, and stream


Quantifying carrying capacity in lotic ecosystems is central to identifying limiting factors and prioritizing restoration actions for native anadromous salmonid populations. Geomorphic and habitat-based monitoring metrics, models, and assessments are available to evaluate ongoing physical limitations in stream reaches. However, these approaches have inherently limited ability to resolve ongoing uncertainties of biologically mediated limitation, such as food preference, food availability, and competition with non-native species. Further, biological assessment tools that use static metrics (abundance, biomass and diversity) cannot directly measure energetic limitations (food availability and trophic routing), and therefore remain inadequate for quantitatively defining biotic limitations, contributing to carrying capacity. Thus, alternative monitoring protocols and subsequent analytical procedures are needed to capture food web processes that directly affect energetic routing.
To understand the effectiveness of habitat restoration treatments designed to increase carrying capacity in co-limited streams, we measured food web responses within a spring creek over multiple years in the Upper Columbia River Basin (WA). We used trophic basis of production and bioenergetic methods to identify and quantify co-limited drivers.

Here we present and discuss: 1) a quantitative food web approach and its associated advantages and disadvantages in the context of stream restoration, 2) initial project results using estimates of energy routing to evaluate habitat restoration and potential impacts of non-native fish, and 3) a new quantitative analysis tool (R package) and its application in a broader management context.