Abstract
A study was conducted in in the Dale River as a part of a stock enhancement programme. The aim was to compare growth and the incidence of precocious maturation between offspring from precocious and large maturing males, and to study genotype‐environment interactions. River and hatchery performance was compared for 5 × 2 maternal half‐sib family groups, which were stocked as 0+ juveniles or maintained in the hatchery throughout. To identify the offspring, the broodfish were characterized by DNA‐fingerprinting (eight microsatellite markers). Smolt size of 1+ hatchery‐reared smolt and fish caught in a smolt trap, and the size and incidence of precocious maturation among 1+ hatchery‐reared parr and 1+ and 2+ parr caught in the river are compared between the families.