The hypothesis was tested that the sagittae of age 2 year Pacific halibut Hippoglossus stenolepis are interchangeable, by analysing whole-otolith preparations for element-to-calcium ratios of 10 trace metals (7Li, 25Mg, 55Mn, 56Fe, 60Ni, 63Cu, 66Zn, 88Sr, 138Ba and 208Pb) and carbon and oxygen stable isotope ratios (13C and 18O). After detrending for significant (α= 0·05) relationships between elemental concentration and otolith mass, significant (paired t-tests, P < 0·01) asymmetry was detected in 13C and 18O, and 88Sr:48Ca. Right (smaller) sagittae exhibited higher 13C and 18O, and lower 88Sr:48Ca, than left sagittae. Significant (α= 0·05) left–right differences were not detected in the remained trace metals. Given that sagittae are the same size at hatch and diverge as H. stenolepis age, the larger otolith is presumably biased towards later-accreted carbonate. Estuarine-reared flatfish probably exhibit more pronounced dissimilarities than observed here, given greater environmental variability in such habitats relative to coastal halibut nurseries, and the importance of salinity and temperature in regulating elemental uptake.
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