Age and growth of Japanese flounder Paralichthys olivaceus from the coastal waters around Kagoshima Prefecture, Japan, using transverse sections of otoliths

Abstract

The ages of Japanese flounder Paralichthys olivaceus sampled from the coastal waters around Kagoshima Prefecture, Japan were determined from 1,009 transverse sections of otoliths. The monthly changes in the percentages of sectioned otoliths with opaque margin revealed that one annulus was formed per year during December to April. Assuming a birth date of February 1 from the monthly change of gonadosomatic indices, ages were assigned to every individual according to the number of opaque zones, and then fitted to the von Bertalanffy growth equations. Estimated equations were Lt = 547.0{1-exp [-0.524(t+0.742)]} for males, and Lt = 844.0{1-exp [-0.284(t+0.789)]} for females, where t is age (year) and Lt is total length (mm) at age t. These two equations were significantly different (p < 0.01) and the total length of females calculated from the equation was larger than that of males except at 1 year old. Growth of released fish did not differ from that of the wild fish in both sexes and the maximum age observed was 18 years for males and 13 years for females. Samples collected from Kagoshima Prefecture showed a higher growth rate than those from the northern Sanriku, Japan.