Tip of The Day - October 25, 2016

Photo by Tom Semadeni

Snowy Road

Origin of Atlantic Salmon

About 80 million years ago, salmon underwent a whole genome duplication event in which they switched from being diploid to tetraploid. Slowly over time, they have drifted back to being diploid, but part of their genome (about 10%) is still tetraploid. There are no genetic markers (SNPs) identified in these regions. I will ignore the tetraploid part of the genome in this simulation project.

An ice glacier covered most of Canada 14,000 years ago and began to recede about 10,000 years ago. Thus, Atlantic salmon did not occupy rivers in Nova Scotia or New Brunswick until the ice had departed. So we can assume that North American Atlantic salmon have existed only in the last 10,000 years, at most. In Europe, pictures of salmon have been found in caves in France and Spain, and on tools made of wood, bone, or antlers dated to be 10,000 years old. If a generation in salmon is 4 years, then there could have been 2500 generations in existence for North American Atlantic salmon.

The European Atlantic salmon have 29 pairs of chromosomes and the North American Atlantic salmon have 27 pairs. Part of chromosome 1 in European salmon joined with chromosome 23, chromosomes 26 and 28 in European salmon merged together, and chromosomes 8 and 29 in European salmon merged together in the North American salmon.

Interestingly, European and North American salmon can interbreed, although the F1 female often does not mature. The F1 male can mature and backcrosses to the parent strains are possible, but all offspring are infertile. The migratory patterns of European and North American salmon in the ocean are similar and the two varieties overlap their territories. With global warming both varieties are migrating further north to the cooler waters. Salmon do not like warm waters (above 20 C). In the simulation, we will not worry about intermixing of varieties, because all fish will be in tanks or sea cages.

Photo by Tom Semadeni

Stream in Snow