Climate Change: Potential Impacts on Juvenile Chinook Salmon Growth in Coastal Environments

To study the impact of projected increases in water temperature on fish growth, changes in juvenile Chinook salmon growth rates during early marine residence were examined under future climate scenarios in Oregon small estuaries and sandy beach surf zones using bioenergetics and habitat specific temperature models using locally obtained data. The Chinook salmon growth curve exhibits a slow increase in growth rate with increasing temperature up to an optimum range, followed by a rapid decline. Under current observed consumption rates and prey energetic density, future increases in temperature (mean±SD: 2.6±1.5°C) would lead to decreased growth rates in both habitats (4.2±3.5%), despite behavioral thermoregulation. Juveniles could compensate for increases in water temperature because the increases in consumption rates or prey energy density (<5%) required to maintain growth at present levels are within the range of current values. However, decreases in growth could be significant in San Francisco Bay, Columbia River and Puget Sound, where temperatures can be >2°C higher than in Oregon nearshore habitats (10.83±1.49°C). Because salmon survival and movement can be related to growth, these results suggest the potential impact of increasing temperatures on populations will depend on the conditions currently experienced with relation to the Chinook salmon growth curve.