Hybridization Dynamics Between a Wild Atlantic Salmon Population and Aquaculture Escapees

The factors determining the vulnerability of wild Atlantic salmon populations to genetic invasion by aquaculture escapees are poorly understood.  The Teno River salmon stock of northern Lapland includes multiple, genetically and demographically distinct wild populations distributed over many tributaries. Scales from >100,000 fish have been collected throughout the Teno for 40 years, generating a long-term genetic dataset with which to monitor changes due to aquaculture influences. Aquaculture escapees have been recorded in the river since the late 1980s.

A full understanding of hybridization between wild salmon and aquaculture escapees requires genetic markers to accurately identify early and later-generation hybrids. Although aquaculture fish comprise multiple distinct lines, areas of the genome responding to domestication selection may show parallel changes over lines and thus collectively discriminate them from wild individuals. We utilized a 220K Atlantic salmon SNP chip and two large reference samples: wild fish collected throughout the Teno before 1985, and escapees caught in the Teno and adjoining coastal waters, to pinpoint such discriminatory regions. Diagnostic SNPs, in combination with the Teno scale archive, will be used to investigate the genetic contribution of aquaculture fish to the Teno populations over time and space and relate it to environmental and demographic factors.