Abstract
Otoliths of Pacific herring (Clupea pallasi) were collected from Puget Sound, Washington, and were analysed for oxygen and carbon isotope ratios (δ18O and δ13C). It was expected that if adult herring spawn at different localities with different δ18O and δ13C values, these isotope variations would constitute a natural tag that can be used to distinguish the herring spawning stocks. For a test project, we took aragonite powder samples from the surface of otolith nuclei and the second summer otolith rings, respectively. Isotopic composition of otolith nuclei from the Georgia Strait had lowest isotope values (from 8.2 to 2.0 VPDB (Vienna Peedee belemnite) in δ18O and 6.8 to 3.9 VPDB in δ13C), significantly different from those collected from two southern Puget Sound spawning grounds (from 3.9 to 0.9 VPDB in δ18O and 5.6 to 2.0 VPDB in δ13C). This isotopic identification is consistent with the biological observation and the actual sample collection. Stable isotopic information extracted from the summer otolith rings, in contrast, showed two types of herring in 1999 corresponding to the migratory and non-migratory stocks in Puget Sound. The rate of the two types of herring was about 70% versus 30%.
Published Version
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