Historically, spring-run and fall-run Chinook salmon have been considered as separate subspecies, races, ecotypes, or even as separate species of fish. A new genetic analysis, however, shows that the timing of migration in Chinook salmon is determined entirely by differences in one short stretch of DNA in their genomes.
Click here for original story, Spring-run and fall-run Chinook salmon aren’t as different as they seem
Source: Phys.org