Investigating thermal windows of juvenile Sockeye Salmon populations in freshwater

The influence of climate warming on the growth of juvenile Fraser River Sockeye Salmon rearing in nursery lakes is poorly understood, particularly in the context of the multiple factors that regulate growth in these environments. This represents a key area where climate change and other forcings may be influencing stock outcomes (i.e. productivity), unbeknownst to fisheries managers.

We aim to fill this gap by reconstructing stock-specific long-term time series of annual growth rates of juvenile Sockeye Salmon in freshwater in relation to their thermal environments. The PSC Scale Laboratory plans to measure an additional 10,000 scales this fall and winter to extend the current existing data of scale growth (1990-present) to 1970 – present. Scales of major Fraser River Sockeye Salmon stocks have been consistently collected by the PSC since 1950s and can be paired with otolith samples since the 1970s. Matching freshwater growth of Sockeye Salmon with adult returns will show the relationships between the freshwater growth and overall survival. Linking freshwater growth with biological factors (e.g. number of spawners) and environmental factors, particularly a large range of temperatures, will quantitatively determine the stock-specific thermal windows and identify the thermal optima.