STRONTIUM CALCIUM RATIOS IN STATOLITHS OF THE NEON FLYING SQUID, OMMASTREPHES BARTRAMI (CEPHALOPODA), IN THE NORTH PACIFIC-OCEAN/

Strontium to calcium ratios were observed. along longitudinal sections of statoliths of nine neon flying squid, Ommastrephes bartrami (LeSue ur, 1821), including three mature females (422 to 454 mm mantle length , ML; 207 to 306 d old) obtained from the North Pacific (27-35 degrees N; 144-150 degrees E) during winter and six immature males and female s (187 to 226 mm ML; 126 to 164 d old) collected from 39 degrees N; 14 5 degrees E and 39 degrees N; 169 degrees W during summer. The distanc es between the nucleus (core) and the edge of the dorsal dome were app roximately 660 to 690 mu m in mature females and 450 to 510 mu m in th e immature squid. Sr/Ca ratios were determined at intervals of 30 mu m between the nucleus and edge of the dorsal dome. Sr/Ca ratios were hi gher in areas near the nuclei and peripheral portions of the dorsal do me than in the middle portions of the statoliths (270 to 420 mu m from the nuclei, corresponding to ages of 60 to 90 d) in mature females; t hus a U-shaped pattern was evident. Sr/Ca ratios in the six immature s quid decreased from nucleus to the dorsal dome; in three squid the rat ios slightly increased toward the dorsal dome edge. The observed Sr/Ca ratios in immature squid were considered to represent younger portion s of the U-shaped pattern. In the present study we discuss this pal:te rn in relation to environmental and biological conditions of O. bartra mi, which undertakes seasonal migrations between spawning grounds in t he Subtropical Domain and feeding grounds in the Subarctic Domain and Transitional Zone in the North Pacific Ocean. Although Sr/Ca ratios ar e potentially affected by ambient water temperature and ontogenetic co nditions, including somatic growth and statolith growth, it was imposs ible to evaluate each environmental and biological effect separately, as variations in these factors are complicated and effects could be in terdependent.