Age and growth of Schizothorax waltoni (Cyprinidae: Schizothoracinae) in the Yarlung Tsangpo river, China

To better understand the biology of Schizothorax waltoni, the age structure and growth characteristics of S. waltoni were examined. The standard length (SL) range was 41-642 mm and the body weight (BW) range was 1.1-3788.1 g. Otoliths continually grew with increasing SL and increasing age, but asymmetrically over time. One annulus was formed each year, between April and July. Estimated age range was 4-37 yr for males, 4-40 yr for females, and 1-9 yr for those of undetermined sex. The SL-BW relationship was described as BW = 1.365 x 10(-5) SL2.984 for females, BW = 1.238 x 10(-5) SL2.999 for males, and BW = 3.664 x 10(-5) SL2.800 for undetermined specimens. The von Bertalanffy function was used to model the observed length-at-age data as Lt = 644.3 {1 -exp [-0.084(t -0.247)]} for females, and Lt = 586.2 {1 - exp [-0.084(t + 2.250)]} for males. Females grew faster than males. Knowledge of this species' characteristics of slow growth and a long life will be useful for establishing reasonable management practices for its conservation.