An assessment of hybridization potential between Atlantic and Pacific salmon

Salmonids possess straying abilities that allows them to exploit open territory and establish new populations. Atlantic salmon (Salmo solar) are expanding their distribution primarily as first-generation escapes from aquaculture, whereas Pacific salmon (Oncorhynchus spp.) are expanding their range in polar and temperate regions due to both anthropogenic and natural influences. Here we utilize artificial intergeneric reciprocal crosses to assess the ability of seven species of Pacific salmon to hybridize with Atlantic salmon. Most cross types were found to produce low numbers of hatched embryos, but none survived to sexual maturation. Survivors consisted of diploids and triploids containing both Atlantic and Pacific salmon parental genomes. Thus, introgression of DNA between Pacific and Atlantic salmon may occur to form F-1 hybrids, but transmission to subsequent generations is expected to be rare and occur only over evolutionary time scales. Further, the low viability observed for the most part at early stages of development and in both reciprocal crosses indicates that intergeneric crosses in nature between Atlantic and Pacific salmon are expected to have severe fitness consequences for both dams and sires.