Tributary-specific variation in timing of return of adult Atlantic salmon (Salmo salar) to fresh water has a genetic component

Abstract

Variation in the timing of return of adult Atlantic salmon (Salmo salar) to rivers contributes diversity to salmon fisheries and is therefore an important effect on their economic value. In this paper, we test two sequential null hypotheses: (i) that run timing does not vary among populations from different tributaries and (ii) that differences in time of return between populations from different tributaries are not evident following transfer to a common location. Adult fish originating from two tributaries of the River Tay, the Almond and Tummel, were caught in local fisheries on different dates. For both tributaries, run timing in two-sea-winter (2SW) fish was earlier than for one-sea-winter (1SW) fish. Within both sea-age classes, recaptures of Tummel fish preceded those from the Almond. After the progeny of Almond and Tummel fish were transferred to a third tributary of the River Tay, the Braan, differences in run timing between the tributary groups were identified for both sea-age classes. The differences were highly consistent with those present in fish that had reared in their native tributaries, indicating a strong heritable component for the run timing trait. Tributary-specific differences in run timing have important implications for the management of seasonally complex fisheries.