Evidence for bottom-up trophic effects on return rates to a second spawning for Atlantic salmon (Salmo salar) from the Miramichi River, Canada

Abstract

Increased return rates of consecutive repeat-spawning Atlantic salmon (Salmo salar) have been noted in the Miramichi River during the past two decades, and the short period for their reconditioning at sea suggests that they occupy the southern Gulf of St Lawrence ecosystem. A 40-year time-series of observations was used to examine linkages between return rates to a second spawning for Atlantic salmon in the Miramichi River and changes in the small fish community of the southern Gulf of St Lawrence that is potential prey for adult salmon. The positive association between the variations in the return rates of repeat spawners and the variations in the small fish biomass index early in the reconditioning year at sea provides evidence that abundant food supplies after return to sea following first spawning may be beneficial for the survival of Atlantic salmon to a second consecutive spawning. In contrast, no association was found between prey availability and return rates of alternate repeat spawners that presumably recondition outside the Gulf of St Lawrence. © 2012 Fisheries and Oceans Canada. Published by Oxford University Press.