Influence of growth and temperature on strontium deposition in the otoliths of Atlantic salmon

Sr:Ca ratios measured in the otoliths of sea-caged Atlantic salmon Salmo salar showed distinct seasonal peaks that were unrelated to water temperature and somatic growth, suggesting other factors have a greater influence on strontium deposition. Atlantic salmon remained in the sea-cages for two seasons, or equivalent to two-seawinter fish in the wild and were subjected to seasonally varying temperatures. Water temperature appeared to be inversely related to the Sr: Ca ratios, but this relationship was statistically not significant. Furthermore, water temperature could not explain the distinct increase in the strontium during the second year. The intensity of the Sr peaks increased in the second season while average winter water temperatures were consistent between years. Additionally, strontium deposition in the otoliths was unrelated to somatic growth. Somatic growth, as evidenced by circuli spacings on the scales, was largely invariant and therefore could not explain the observed peaks. Though not explicitly measured, the data are consistent with the notion that strontium deposition is a function of maturity state in Atlantic salmon. (C) 2004 The Fisheries Society of the British Isles.