Age and growth of cutlassfishes, Trichiurus spp., from the South China Sea

Age and growth of two species of cutlassfishes, Trichiurus spp. (Trichiuridae), from the South China Sea were examined. Between December 1996 and November 1997, 1495 specimens were collected from coastal waters near Hong Kong. Two species, Trichiurus lepturus and T. nanhaiensis, were harvested and ages of specimens were estimated by using transverse sections of the sagittal otoliths. Opaque growth rings were verified to have formed annually during February. Lee's phenomenon was not observed for either species, although T. lepturus tended to display reverse Lee's phenomenon. Otolith weight was linearly related to age, and accounted for about 72% and 76% of the variation in age (t) for T. lepturus and ir: nanhaiensis, respectively, comparable to the von Bertalanffy growth models in preanal length (PL). For older fish, otolith weight provided a more precise estimate of age than preanal length. Preanal length and age were fitted to the von Bertalanffy growth model by nonlinear regression, resulting in PL (mm) = 589{1 - e[-0.168 ((t + 2.682)])} (T. lepturus); PL (mm) = 602{1 - e([-0.207 (t + 2.044))} (T. nanhaiensis). Growth in length of the two species was significantly different (ANCOVA, F-2,F-1245=169.69, P<0.001).