Reproduction of cutlassfishes Trichiurus spp. from the South China sea

Cutlassfishes, Trichiurus Linnaeus, 1758, are the most important commercial marine fish species of China in terms of weight and they are found in all Chinese waters. However, no study has been conducted on the populations of Trichiurus in the South China Sea. The aim of this study was to investigate the reproduction of the populations of Trichiurus spp. in the South China Sea. In a 12 mo sampling period between December 1996 and November 1997, 14 95 specimens of T. lepturus and T. nanhaiensis were collected from Hong Kon g coastal waters. Spawning period and reproductive cycle were studied by ch ecking the temporal profile of the Relative Gonadal Index/Gonosomatic Index , and by examining ovaries macroscopically and whole oocytes microscopicall y. All 3 methods provided similar results: the spawning periods of T. leptu rus and T, nanhaiensis were March to June and April to August, respectively Both species were found to practice group-synchronous spawning and mature females are capable of spawning more than once each spawning season. The me an preanal lengths at sexual maturity of T. lepturus and T, nanhaiensis fem ales were 255 and 282 mm respectively. The sex ratios of both species were significantly different from 1:1 among different sampling months, and diffe rent age and size ranges.