Dataset for: Spatial and environmental effects on Coho Salmon life-history trait variation

Adult size, egg mass, fecundity and mass of gonads are affected by trade-offs between reproductive investment and environmental conditions shaping the evolution of life-history traits among populations for widely distributed species. Coho salmon Oncorhynchus kisutch have a large geographic distribution and different environmental conditions are experienced by populations throughout their range. We examined the effect of environmental variables on female size, egg size, fecundity, and reproductive investment of populations of Coho Salmon from across British Columbia using an information theoretic approach. Female size increased with latitude and decreased with migration distance from the ocean to spawning locations. Egg size decreased with average intragravel temperature during incubation, migration distance, in larger rivers, but increased in rivers that were lake headed. Fecundity increased with latitude, warmer temperature during the spawning period, and river size, but decreased in rivers that were lake headed compared to rivers with tributary sources. Gonadal somatic index increased with latitude and decreased with migration distance. Latitude of spawning grounds, migratory distance and temperatures experienced by a population, but also hydrologic features – river size and headwater source – are influential in shaping patterns of reproductive investment, particularly egg size. The lack of an effect of latitude on egg size suggest that local optima for egg size may drive the positive relationship between egg number and latitude – a pattern that is partially off-set by larger female size and gonadal somatic index with latitude.