MICRO-RAMAN SPECTRAL STUDY OF VATERITE AND ARAGONITE OTOLITHS OF THE COHO SALMON, ONCORHYNCHUS KISUTCH

Abstract Raman spectra of naturally occurring vaterite and aragonite have been recorded from the otolith of the coho salmon Oncorhynchus kisutch (Teleostei: Salmonidae). Multi-channel micro-Raman spectroscopy has made it possible to measure vaterite and aragonite spectra with high signal-to-noise ratios and with spatial resolutions across otoliths of 1–5 μm. Vaterite Raman spectra show both a shift and the presence of multiple bands in the region of the characteristic calcium carbonate symmetrical stretching ( v 1 ) and in plane bending v 4 modes, as well as vaterite-specific bands at 266 and 301 cm −1 in the low frequency region. The low frequency Raman-active lattice modes of vaterite are reported here for the first time.