Life History and Smoltification Shape Genomic Signatures of Thermal Tolerance in Chinook Salmon

This project investigates how thermal tolerance is shaped by life history and developmental transitions in Chinook Salmon (Oncorhynchus tshawytscha) from southern British Columbia. Chinook Salmon display distinct ecotypes, stream-type and ocean-type, that differ in the duration of freshwater residency and timing of smoltification, the developmental process that prepares juveniles for transition to seawater. We studied four populations representing these ecotypes to understand how smoltification and life history influence thermal resilience across environments. The project combines physiological assays with two types of genomic datasets: RNA sequencing (RNA-seq) of gill tissue to assess gene expression, and pooled whole-genome sequencing (PoolSeq) of individuals with high and low thermal tolerance (CTmax) to identify genetic variants associated with thermal performance. By integrating population-specific gene expression profiles and allele frequency differences, this research aims to identify key pathways and regulatory mechanisms involved in thermal stress responses. The results contribute to a broader understanding of how environmental and evolutionary factors interact to influence climate resilience in a culturally and ecologically important species.