CHARACTERISTICS OF AGE AND GROWTH OF SCHIZOTHORAX CURVILABIATUS IN THE LOWER REACHES OF THE YARLUNG ZANGBO RIVER

Estimating age structure of fish populations and growth of individuals are fundamental to assessing fish population dynamics and formulation of effective fisheries management. Obtaining accurate age information is the first step for precise understanding of these metrics. As one of the dominant species in the lower reaches of the Yarlung Zangbo River, little is known about the age estimations of Schizothorax curvilabiatus. 928 specimens of S. curvilabiatus were collected from December 2015 to November 2016 in the Motuo reach. Otoliths, vertebrae and opercular bones were examined to assess the suitability of the three calcified structures for age estimation. The results showed that otoliths were more suitable than vertebrae and opercular bones for age estimation of S. curvilabiatus. The standard length (SL) of S. curvilabiatus ranged from 48 to 508 mm, weight (W) ranged from 1.8 to 1898.9 g. The range of estimated age was 2—23 years for males, 2—43 years for females, and 1—4 years for those of undetermined sex. S. curvilabiatus populations in the Motuo reach were dominated by the specimens of 3—5 years. The intercept of length-weight relationship showed no difference between sexes and the function was described as W=2.279×10^–5 SL^2.931. The von Bertalanffy function was used to model the observed length-at-age data as L_t=590.2 1–e^{–0.096(t–0.282)}, W_t=3016.8 1–e^{–0.096(t–0.282)2.931} for females, and L_t=575.3 1–e^{–0.090(t+0.011)}, W_t=2798.9 1–e^{–0.090(t+0.011)2.931} for males. The inflexion point for the growth of females and males were 11.5 and 11.9 years, respectively. Accordingly, reasonable conservation measures, such as controlling fishing, habitat protection and strengthening artificial breeding, are needed to maintain the fish stock for future generations due to the increasing anthropogenic activities in the lower Yarlung Zangbo River.