Response diversity among tributaries with variable flow permanence patterns buffers salmonid spawning habitat availability to interannual snowpack variation

Intermittent tributaries can support spawning activities of native fishes if they flow long enough and warm enough for offspring to develop and access perennial habitats. As climate change alters streamflow permanence patterns, it is critical to understand how this may impact the availability of spawning habitats to native fishes. Here, we describe the spatio-temporal variability in annual spawning suitability of intermittent and perennial tributaries in an Intermountain West river basin, and how these conditions are impacted by watershed physiographic and annual climatic conditions. We assessed spawning suitability of tributaries as the window of days during which the eggs of spawning individuals would be able to accumulate sufficient degree days to hatch and emerge before the stream dried or the growing season ended. In the low snowpack year, suitable spawning habitat was concentrated in perennial tributaries, as intermittent streams did not support sufficient surface flows. However, in a subsequent high snowpack year, intermittent tributaries provided extensive suitable spawning habitat, while perennial tributaries demonstrated reduced suitability due to cold temperatures. Importantly, the total suitable spawning window across the basin remained relatively constant between years, as suitability gains in intermittent tributaries balanced the losses in perennial tributaries. Our results highlight how the interaction between flow duration and temperature complicates predictions about how increased intermittency under climate change can be expected to impact native fishes.

Primary Presenter: Timothy Walsworth, Utah State University (timothy.walsworth@usu.edu)

Authors:

Timothy Walsworth, Utah State University  (timothy.walsworth@usu.edu)

Skylar Rousseau, Utah State University  (a02389989@usu.edu)