PNNL

Abstract

Predicting the consequences of climate warming for Pacific salmon depends importantly on information about bioenergetic responses to thermal variation. A major challenge is that such responses can be difficult to study in natural environments. We experimentally constructed a temperature-dependent, otolith – water fractionation relationship for oxygen isotopes (?18O) in Chinook salmon by rearing juvenile fish at nominal temperatures from 6 to 21°C. Temperature and otolith precipitation rate had significant effects on the otolith – water ?18O fractionation, but somatic growth rate did not. The slope of the ?18O fractionation equation also differed significantly from that of inorganic aragonite. Our results suggest expression of kinetic effects on ?18O fractionation in the otoliths of Chinook salmon near their pejus temperature, but these are likely confounded by other physical and physiological processes involved in otolith formation. Species-specific ?18O fractionation equations have considerable utility to reconstruct temperature history in Pacific salmon, but ensuant inferences should recognize the potential for analytical error arising from interacting vital effects.