Salmon are shrinking, and it shows in their genes

Male salmon are maturing earlier and becoming smaller, and it shows in their genes. This was the discovery of a study that examined scale samples from salmon in the River Teno in Northern Finland over a 40-year period, and looked at the population genetic profile of a gene that determines salmon's age of maturity and size. The results show that the 'big salmon gene version' has become rarer in the population over time, and has been replaced by the 'small salmon gene version'.

The study, conducted by scientists from the University of Helsinki in co-operation with Natural Resources Institute Finland and the University of Turku, was published in the journal Nature Ecology and Evolution and was featured on the magazine's November issue's cover.

Work - Consortium - Age - Mature - Size

Previous work by the consortium has shown that the age at which salmon mature is getting younger, and consequently also the size of salmon that are spawning is getting smaller. They also identified a single gene Vgll3 that has a large influence in determining the age at which salmon reach sexual maturity. They identified two forms or alleles of the gene that appear to signal to the salmon to either mature later at a larger size or mature earlier at a smaller size. The later salmon mature, the bigger they grow.

"We knew from our earlier research that the age at maturity had been decreasing over this period. Now we wanted to see if there were signs of this also at the genetic level, that is, whether it was an evolutionary change," professor Craig Primmer from the Faculty of Biological and Environmental Sciences at the University of Helsinki explains.

Evolution - Changes - Genes

"Basically, if we see that 'salmon are shrinking', we can't be sure if it is evolution. For that, we need to know there are also changes in their genes. Now we also...