Stock identification of cultured fish and shellfish by composition of trace elements in the hard tissues : a new technology for identification of product origin.

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For trace-elemental fingerprint studies in fish otoliths, industry-coupled plasma mass spectrography (ICPMS) has not used in Japan. The present study was undertaken to develop ICPMS-based trace-elemental fingerprint studies in the hard tissues of cultured fish and shellfish in Japan. Following results were obtained.1. We developed standard methods to determine trace-elemental composition of fish otoliths and shells of shellfish using solution-based and laser abration ICPMS. Trace-elemental compositions were useful fingerprints that could identify product origin of cultured species.2. We clarified migratory patterns of some salmonid and eel species using Sr contents and Sr/Ca ratio of otoliths determined by EPMA and revealed that the method is a powerful tool to study migration patterns of anadromous, catadromous or diadromous fishes.3. We developed a DNA microarray to identify stocks of chum salmon. The array was accurate and time effective, and required no special equipments such as DNA sequencer. Therefore, the method is especially a powerful tool to identify chum salmon stocks in the field study and on board.4. We immunohistochemically localized otolith matrix proteins, OMP-1 and otolin-1, and suggested important rolls of these proteins in calcification and formation of otolith micro structures. We also revealed that the aragonite saturation ratio of endolymph was maintained over 1.0 through the day-night cycle, suggesting aragonite crystal growth could be continued through a day. On the other hand, mRNA expression of otolin-1 showed clear daily rhythm with significantly higher expressions during night-time, suggesting a key fuction of otolin-1 to construct daily rings. In masu salmon, increases in Sr concentrations and Sr/Ca ratios in the serum occurred 7 days after the seawater transfer. Such a time-lag must be taken into account to reconstruct migration patterns in the anadromous fishes.