Nippon Suisan Gakkaishi 75 (3), 419-424 (2009)

Use of otolith microchemistry to estimate the migratory history of Japanese dace Tribolodon hakonensis in the Kamo River, Mie Prefecture

DAISUKE ISHIZAKI,1 TSUGUO OTAKE,2 TATSUYA SATO,1
TAIGA YODO,1* MOTOI YOSHIOKA1 AND MASAAKI KASHIWAGI1

1Graduate School of Bioresources, Mie University, Tsu, Mie 514-8507, 2International Coastal Research Center, Ocean Research Institute, the University of Tokyo, Otsuchi, Iwate 028-1102, Japan

The diadromous migratory history of Japanese dace Tribolodon hakonensis in the Kamo River, Mie Prefecture, was studied by examining the concentrations of strontium (Sr) and calcium (Ca) in their otoliths (lapillus) using wavelength dispersive X-ray spectrometry on an electron microprobe. In the rearing examination, individuals which were collected in freshwater and acclimated to a seawater environment (20-37‰) showed a Sr:Ca ratio increase in the otolith. The relationship between otolith radius and standard length of Japanese dace fitted well to the logistic regression model. These results indicate that otolith microchemistry analysis is effective for clarifying the migratory history of Japanese dace. This analysis showed that 93 of 94 specimens collected from spawning aggregations in the Kamo River, had seawater-dwelling experience. In those specimens, the standard length at seaward migration was back-calculated as 18-152 mm except for two specimens. The seaward migration age corresponded to age 0 to 1 from the age and standard length distribution of Japanese dace in the Kamo River.


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