Elemental chemistry of left and right sagittal otoliths in a marine fish Hippoglossus stenolepis displaying cranial asymmetry

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 (δ¹³C and δ¹⁸O). 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 δ¹³C and δ¹⁸O, and ⁸⁸Sr:⁴⁸Ca. Right (smaller) sagittae exhibited higher δ¹³C and δ¹⁸O, 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.