Genetic and life history differentiation between donor and derivative populations of Atlantic salmon

We examined the genetic structure of two North American populations of Atla ntic salmon Salmo salar, those of the Connecticut and Penobscot rivers, The native population in the Connecticut River (at the southern edge of the sp ecies' natural distribution) was extirpated nearly 200 years ago. A restora tion population was founded about 30 years ago with individuals from the Pe nobscot River, 400 km north of the Connecticut River. We investigated the c urrent variation of both populations at enzymatic and microsatellite loci t o assess the genetic changes that have occurred in the Connecticut River po pulation with respect to the predominant (brood source) population. Signifi cant differences between the two stocks were found at both enzyme and micro satellite loci and in the age of maturity of returning adults.