Multi-way analysis of trace elements in fish otoliths to track migratory patterns

Spawning striped bass in the Shubenacadie watershed of Nova Scotia, Canada exhibit three dorsal coloration patterns: green, indicative of fish from the ocean; black, indicative of fish that overwinter in a fresh headwater lake, and mottled fish of unknown origin. Microchemical analysis of growth rings in fish otoliths (calcareous particles found in the inner ear of certain lower vertebrates), measured by laser ablation-inductively coupled plasma/mass spectrometry (LA-ICP/MS), from fish captured during the 1999 Shubenacadie spawning period were analyzed by Tucker-3 multi-way principal component models. Using this technique, multidimensional patterns were discovered in the trace element measurements indicating that migratory patterns of individual striped bass can be tracked from the time-dependent trace element record deposited in the otoliths. Of the nine fish analyzed by LA-ICP/MS, trace element composition at year 0 suggested that all nine fish originated from the same locale. Differentiation in the trace element record was observed in subsequent years. Clustering of the trace element data for six fish unambiguously coincided with dorsal coloration. The three remaining fish exhibited trace element patterns that suggested migration between freshwater and marine conditions at one or more periods during life.