Retrospective growth analyses of Chum salmon (Oncorhynchus keta) in relation to adult returns and environmental factors

Due to the complicated life history of Pacific salmon, which environmental factor (s) has major influences on their growth and productivity remains unknown, particularly accounting for their entire life history. Most previous studies focus on the short time period when they first enter the ocean. We will fill the gap by investigating salmon growth in all their marine years. We plan to use Chum salmon in southern British Columbia as an example to address this question because Chum salmon migrate to the ocean right after hatching, providing the great candidate to compare marine growth in the multiple years and seasons.
We propose to process the historic scales, measuring the seasonal (summer and winter separately) growth and identifying stocks, to reconstruct stock-specific long-term time series of growth rates of Chum salmon in multiple ocean years. Fish scales provide a record of individual growth during their entire life history and have long been used to study age structure and growth. The scales of Chum salmon have been consistently collected with fish length measured during a test fishery in Johnstone Strait since 1980. In recent years, along with the scales, tissues for genetic stock identification have been collected and processed on a fairly consistent basis from that test fishery. The number of stock-specific adult returns (2008-2019) can be estimated using the Chum Genetic and Environmental Management Model (ChumGEM) based on recent catch, escapement, and the genetic data.

By linking growth rates of Chum salmon stocks with density dependence and ocean conditions (1980-2019), this project will attempt to define which environmental factor(s) would be the best indicator of returns for each stock; by linking growth rates of Chum salmon stocks with the stock-specific adult returns, this project will determine which season and year of growth rate would be the best indicator of adult returns for each stock.