Impact of Changes in Streamflow and Temperature on Endangered Atlantic Salmon

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Coastal rivers draining into the Gulf of Maine are home to the endangered Gulf of Maine Distinct Population Segment of Atlantic salmon. The Gulf of Maine population began to decline significantly by the late 19th century, leading to the closure of the commercial Atlantic salmon fishery in 1948. In recent years, populations have again begun to decrease again. State and federal fisheries biologis...

Coastal rivers draining into the Gulf of Maine are home to the endangered Gulf of Maine Distinct Population Segment of Atlantic salmon. The Gulf of Maine population began to decline significantly by the late 19th century, leading to the closure of the commercial Atlantic salmon fishery in 1948. In recent years, populations have again begun to decrease again. State and federal fisheries biologists are concerned that climate-related changes in streamflow and temperature could impact salmon survival in these rivers. Projections of future climate conditions for the Northeast indicate warming air temperatures, earlier snowmelt runoff, and decreases in streamflow during the low flow period (summer). In the spring, snow melts in the Northeast and recharges groundwater supplies. As climate conditions change, snow is melting earlier, resulting in longer periods of low streamflow in summer. These changes are of concern because this period is critical in the Atlantic salmon life cycle.

 

The goal of this project was to investigate changes in summer low streamflow and stream temperatures to identify how endangered Atlantic salmon populations might be affected by these changes. Researchers assessed past changes in groundwater discharge to rivers in the Gulf of Maine using historical flow data and estimated future streamflow, temperature, and groundwater discharge during summer low-flow periods using climate-model data and detailed watershed models.

 

A main result of this work was the development of a watershed model for four rivers in Maine that provide important habitat for Atlantic salmon: The Pleasant, Narraguagus, Sheepscot, and Royal Rivers. Researchers developed models of these river basins that provide daily streamflow, which enables managers to characterize the timing and quantity of water moving through each basin. This information can then be used to test how different streamflow and water temperature conditions might impact salmon.

 

This research expands our knowledge of the effects of climate-related changes on Atlantic Salmon, and can help managers make more informed decisions on the management of these ecosystems, given projected future changes in climate.