Assessing the Impact of Altered Peak Flow Regimes on Salmon Populations
Abstract
Peak annual streamflow can play an important role in the biophysical interactions of fluvial habitats. In the case of salmonids, peak flows can scour the channel bed, resulting in reduced survival during the egg incubation stage. Current climate projections for the northwestern United States show significant changes in rainfall patterns, altering the timing and magnitude of winter floods. However, these impacts can vary significantly between species within the same ecosystem. The goal of this study was to examine the impact of changing frequency and magnitude of peak flows on salmon spawner abundance. Using an empirical relationship between peak flow and juvenile survival combined with a lifecycle model, we examined four species (spring-run Chinook salmon Oncorhynchus tshawytscha , fall-run Chinook salmon O. tshawytscha , coho salmon O. kisutch , steelhead O. mykiss ) within the Chehalis River, Washington State, USA. We stochastically generated a time series of floods based on recurrence intervals from recent gage data. In the life cycle model, we then related these annual floods to a survival change for the egg incubation stage based on an empirical relationship between peak flows and egg to outmigrant survival rates. Future increases in peak flows decreased the annual incubation survivals, and the model predicted decreasing spawner abundance as a result of climate change. In our results spring and fall Chinook were the most sensitive to changing winter flow regimes, while coho salmon and steelhead populations were likely to be limited by survival during later rearing stages. By augmenting both the recurrence of peak flows as well as habitat quality and availability, this assessment indicates the potential impact of peak flow variability on spawner abundance and gives an indication of which restoration actions will have the most benefit.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMEP41C2329N
- Keywords:
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- 0442 Estuarine and nearshore processes;
- BIOGEOSCIENCES;
- 0481 Restoration;
- BIOGEOSCIENCES;
- 1813 Eco-hydrology;
- HYDROLOGY;
- 1825 Geomorphology: fluvial;
- HYDROLOGY