Modelling climate change effects on Atlantic salmon: Implications for mitigation in regulated rivers

Area of Science:

• Environmental Science
• Climate Science
• Fisheries Science

Background:

• Climate change is predicted to significantly alter river temperature and discharge regimes.
• River flow and temperature are critical factors influencing the survival and life history of aquatic species, particularly Atlantic salmon.
• Regulated rivers present unique challenges and opportunities for managing aquatic populations under changing climate conditions.

Purpose of the Study:

• To investigate the impact of climate-induced changes in water temperature and discharge on Atlantic salmon abundance in a regulated river.
• To explore mitigation strategies for negative climate change impacts on salmon populations through regulated discharge regimes.
• To assess the effectiveness of different climate models and scenarios on predicting future salmon population dynamics.

Main Methods:

• Utilized a spatially explicit individual-based model to simulate juvenile Atlantic salmon population abundance.
• Employed climate data from Hadley Centre's GCM HadAm3H and Max Plank Institute's GCM ECHAM4 to generate future temperature and discharge scenarios.
• Compared predicted populations under future scenarios with control scenarios representing past conditions and simulated different minimum discharge regimes.

Main Results:

• Juvenile Atlantic salmon (parr) abundance decreased across all future climate scenarios compared to control conditions, primarily due to reduced wetted areas.
• The extent of population decrease varied depending on the specific climate scenario, Global Climate Model (GCM), and GCM spatial domain.
• Increasing the minimum permitted discharge significantly increased the abundance of both parr and smolt in three out of four examined GCM/GCM spatial domains.

Conclusions:

• Climate change poses a significant threat to Atlantic salmon populations in regulated rivers through altered hydrological conditions.
• Implementing strategic water releases from reservoirs during critical periods for juvenile salmon can effectively mitigate the negative impacts of climate change.
• Regulated rivers with upstream storage capacity offer a viable management approach to enhance salmon resilience to climate change.