Nippon Suisan Gakkaishi 73 (5), 859-866 (2007)

Changes in otolith microstructure and microchemistry of two Siganid fishes during settlement period

HIDEAKI YAMADA AND TAKURO SHIBUNO

Ishigaki Tropical Station, Seikai National Fisheries Research Institute, Fisheries Research Agency, Ishigaki, Okinawa 907-0451, Japan

Otolith microstructure and microchemistry were examined in the early life stages of Siganus guttatus and S. fuscescens collected around the Yaeyama Islands, Okinawa Prefecture. The formation of a settlement mark, characterized by a rapid decrease in otolith increment width, was found to occur at settlement of both species. Otolith Sr:Ca ratios, analyzed using an electron probe micro analyzer (EPMA), were relatively constant in the pelagic larval period, followed by an increase in the ratio 4-5 days before settlement. This microchemical change associated with settlement was independent of year class and species in spite of the fact that the nursery grounds of both siganid fishes are distinct in environmental conditions. These results suggest that otolith Sr:Ca ratios at the pre-settlement stage of the two siganid fishes are endogenously controlled.


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