Age, growth and age composition of tonguefish, Cynoglossus abbreviatus, in the central Seto Inland Sea, Japan

Abstract

We examined age and growth by thoroughly observing otolith sections of tonguefish, Cynoglossus abbreviatus, caught by small trawl nets in the central Seto Inland Sea, Japan, from November 1998 to March 2000. Seasonal change in the proportion of opaque zone at the otolith margin showed that an opaque zone was formed each year from April to June. The Von Bertalanffy growth equations were estimated as follows: TL_t=265.2 (1-e^{-0.91(t+0.325)}) for males and TL_t=328.1 (1-e^{-0.96(t+0.023)}) for females, where TL_t is the total length (mm) at t (year). These equations were significantly different between male and female. Age composition of fisheries landings ranged from 0+ to 6+ and 5+ for male and female, respectively, and showed a large proportion of the landings were immature fish under 2+.