The influence of environmental variables on larval development of coho salmon (Oncorhynchus kisutch), with specific focus on the influence of near-freezing incubation temperatures, was examined across populations within British Columbia. A survey across the geographical distribution within British Columbia was conducted to determine the range and variability of incubation temperatures experience by incubating coho salmon. Temperatures throughout incubation differed significantly among locations, averaging approximately 1 °C in colder interior locations and approximately 5 °C in warmer coastal locations. Environmental variables influenced egg size, fecundity, female size and gonadal somatic index, such that higher latitude of spawning grounds increased, larger systems decreased, and increased temperatures experienced by a population increased the four life-history traits. Suggesting significant effects of latitude of spawning grounds, size of spawning system and temperatures experienced by a population on shaping patterns of reproductive investment. ...