Somatolactin mRNA expression during the parr-smolt transformation in hatchery-reared Atlantic salmon Salmo salar smolts

Expression of somatolactin (SL) mRNA was quantified during smoltification at 2 week intervals during January and February and weekly during March, April and May 2004 in a line‐bred ranching stock of Atlantic salmon Salmo salar. Gene expression of SL (and a splice variant termed SL180) was lower in fish sampled in the later weeks of smoltification than in those at the beginning, a pattern opposite to that of gill Na+ K+‐ATPase activity.