Atlantic salmon farming is moving towards extended periods of land-based production to minimise the time at sea, but this increases the risk of unwanted male sexual maturation. As the timing of puberty is driven by genetics (e.g. vgll3) and the environment, we used a domesticated strain of vgll3 heterozygous broodstock to produce three all-male half-sibling families (A-C) using three different production regimes to assess the timing of first puberty. Firstly, “large smolts” were produced in a flow-through system on 13°C freshwater and constant light from first feeding (day 0) up to 1kg (day 354). Genetics explained a significant (p<0.05) amount of the variation, with 93, 71, and 34% of the expected early (EE), intermediate (EL), and late (LL) maturing vgll3 genotypes being pubertal on day 354, respectively (Figure 1A). Secondly, “post-smolts” were produced by switching half the large smolts to 13°C seawater at 420g (day 272) and growing them in tanks to 0.95kg (day 354). This led to a significant 14% reduction in the total incidence of puberty by day 354 compared to the large smolts (Figure 1B). However, the regulation of pubertal timing by vgll3 did not interact with salinity. Thirdly, traditional “under-yearling” smolts were produced using periods of natural or manipulated temperature and photoperiod, followed by transfer to a sea-cage at 150g in December (day 290) where they stayed for one year until harvest at 4.8kg (day 648). None of these fish were mature at sea transfer, but 9% were at harvest, with 22, 7, and 2% of the early, intermediate, and late vgll3 genotypes being mature, respectively. When comparing the regimes, family effects outside of vgll3 on the prevalence of sexual maturation were significant for the large-smolt regime, but not in the under-yearling regime (Figure 1C). In conclusion, i) selecting for the late vgll3 allele is an effective method to delay puberty over a range of production regimes, ii) family effects outside of vgll3 were not consistent across regimes, and iii) using seawater reduced the incidence of precocious puberty during land-based production.