STRONTIUM-CALCIUM RATIOS IN JUVENILE ATLANTIC HERRING CLUPEA-HARENGUS L OTOLITHS AS A FUNCTION OF WATER TEMPERATURE

The effect of environmental temperature on the atomic concentration ratios of strontium to calcium in fish otoliths was investigated for young-of-the-year juvenile Atlantic herring Clupea harengus L. which were captured from the wild and held in the laboratory for 1 yr. The fish were maintained in large volume, flowing seawater tanks and were subject to the seasonal temperature cycle of Maine coastal waters ( almost-equal-to 2-18-degrees-C). Otolith Sr/Ca ratios were measured for 136 fish and related to temperature by a hyperbolic Michaelis-Menten function. The greatest temperature effect occurred at lower temperatures, where Sr/Ca ratios increased with decreasing temperature. There was less of an effect at warmer temperatures where the Sr/Ca ratios approached an asymptote. The results are interpreted in terms of the effect of environmental temperature on the physiological processes that result in a discrimination against the passage of strontium from seawater into the saccular endolymph which baths the otoliths. We suggest that at lower temperatures, where those physiological processes become slowed or impaired, strontium passes more readily into the endolymph and becomes incorporated into the otolith aragonite, thus supporting the use of otolith Sr/Ca ratios in studies of life histories of fishes at environmental extremes.