Inter- and intrapopulation variation in temperature sum requirements at hatching in Norwegian Atlantic salmon

The duration of the ontogenetic development of the eggs up to hatching time was studied under stable water temperatures for a total of 47 families (th e offspring of a single pair of spawners) from eight wild populations and o ne domesticated stock of Norwegian Atlantic salmon. Eggs From each family w ere incubated at stable water temperatures of 7.3 and 9.4 degrees C. The nu mber of days required to 50% hatching differed significantly between popula tions for both experimental temperatures together and for each temperature separately. The interpopulation and intrapopulation Variation each accounte d for about 50% of the overall variation. Significant differences were foun d for the days required to 50% hatching between eggs of the domestic stock from The Norwegian Salmon Breeding Company and two natural populations and between some of the wild populations. It is concluded that the lime require d from fertilisation to hatching in Atlantic salmon is a population-specifi c adaptive trait. (C) 1999 The Fisheries Society of the British Isles.