Age and growth of the yellowbelly threadfin bream Nemipterus bathybius in Kagoshima Bay, southern Japan were examined using sectioned otoliths of 1359 fishes collected from April 1998 to November 2000. Monthly changes in marginal growth increments indicated that ring marks (outer edge of opaque zone) were formed once a year between May and August. Assuming a birth date of 1 July from the monthly change of gonadosomatic index, ages ware assigned to every individual according to the number of ring marks. Length-at-age and weight-at-age data were best fitted to the von Bertalanffy among the three growth models. Equations obtained were FL_t = 274.7(1 -exp(-0.341(t+ 0.762))) for males and FL_t = 231.0(1 - exp(-0.161 (t+ 4.405))) for females, where t is age (year) and FL, is the fork length (mm) at age t, and they were significantly different (i.e. males grew faster than females). Maximum age observed was approximately 8 years for males and approximately 10 years for females.
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