Stock-Specific Variability in Productivity as a Function of Juvenile Fish Condition and Abundance in Freshwater

The energetic condition and abundance of juvenile sockeye salmon from several key Fraser sockeye rearing lakes have been examined in detail by DFO’s Freshwater Ecosystems Section for the past five years. Key results from this research include: stock-specific variability in energetic condition of smolts – reflective of variability in lake productivity; interannual variability in smolt condition (e.g. storage lipids) and abundance that are consistent with direct density dependence growth (e.g. large spawning escapements); interannual variability in fall fry condition- consistent with delayed density dependence; and variability in stocks on the portion of individuals at or near critical minimal energy levels – potentially predictive of future stock-specific marine survival. These results have implications for setting spawning escapement targets, restoration activities, and ultimately harvest allocations for different stocks. However, given this research is novel and there are only a limited number of years for which this data are available, advice based on a few years of information would be highly uncertain.

We propose to continue this research and strategically monitor stock-specific variability in energetic condition (plus other metrics of fish condition) in conjunction with estimates of abundance (i.e. Hydroacoustics estimates, fence counts) for a broader mechanistic understanding of juvenile energy dynamics in relation to survival. The results of this project will provide a better understanding of the factors that limit both sockeye survival and condition in freshwater lakes. Interannual and stock-specific variability in smolt condition may also provide insight into the early marine survival of Fraser sockeye.