Age and growth of red tilefish Branchiostegus japonicus from western Wakasa Bay, Japan, based on otolith analyses using the cross-section and surface methods

摘要

Age and growth of red tilefish Branchiostegus japonicus caught from June to December, 2012 in western Wakasa Bay, Japan, were investigated based on otolith analyses using the cross-section and surface methods. Assuming annual formation of ring marks and a hatching date of September 1, which was inferred based on observed monthly change in the proportion of mature females (GSI >= 2.5), ages were assigned to individuals according to the number of ring marks in the sectioned otoliths. Since there were almost no one-or two-year-old fish specimens sampled, back-calculated length data of these fish were complemented using otoliths of ring groups 1. 3 by the surface method. Briefly, the first and second ring radii of each specimen were substituted into relational expressions between otolith radius and standard length of females and males. Length-at-age data were fitted to the von Bertalanffy growth equations by a non-linear least squares method. The equations were estimated as follows: Lt=276 (1-exp(-0.490(t-0.215))) for females and Lt=389(1-exp(-0.320(t-0.0483))) for males, where Lt is the standard length (mm) at age t. The maximum ages observed were 18 and 14 years for females and males, respectively.