Salmon have complicated DNA that, at some point in the past, was completely duplicated. These duplicated genomes are hard to sequence because every gene has multiple copies, and in the past, duplicated genes were filtered out before studies were conducted on how salmon adapted to different environments. But new work on humans, yeast and rats shows that duplicated genes are often responsible for important adaptations. Now, geneticists at SAFS have developed a new method that enables study of gene duplicates in Pacific salmon, and have found that variation within these formerly unstudied genes is responsible for when salmon return from the sea, differences in body shape and size, and even whether individuals from the same species choose to migrate to the sea (sockeye salmon) or not (kokanee). These approaches will unleash a new wave of important studies to better inform fisheries and hatchery managers of genetic variation important for response to climate change, response to pollution, or disease resistance. The new research was authored by SAFS postdoc Morten Limborg, Wesley Larson, and SAFS professors Lisa Seeb and Jim Seeb, and appears in Molecular Ecology.