Age and Growth of Oxygymnocypris stewartii (Cyprinidae: Schizothoracinae) in the Yarlung Tsangpo River, Tibet, China

Bin Huo, Cong-Xin Xie, Bao-Shan Ma, Xue-Feng Yang, and Hai-Ping Huang (2012) Age and growth of Oxygymnocypris stewartii (Cyprinidae: Schizothoracinae) in the Yarlung Tsangpo River, Tibet, China. Zoological Studies 51(2): 185-194. To better understand the biology of Oxygymnocypris stewartii and its relationship with management considerations, the age and growth of O. stewartii were examined using sectioned otoliths of 712 specimens collected from Aug. 2008 to Aug. 2009. The standard length (SL) ranged 45-587 mm. The location of the 1st annulus was validated by a daily growth increment (DGI) analysis of otoliths. Monthly changes in the marginal increment ratio of the otoliths with 1-8 annuli indicated that an annulus forms once a year, from Mar. to June. The index of the average percentage error (IAPE) of the sectioned otoliths was 0.5%, and the coefficient of variation (CV) for the age estimation was 0.7%. Estimated ages ranged 3-17 yr for males, 2-25 yr for females, and 1-6 yr for those of undetermined sex. The SL-BW relationship was described as BW = 6.108 × 10-6 SL3.126 for females, BW = 9.872 × 10-6 SL3.052 for males, and BW = 3.203 × 10-5 SL2.821 for undetermined. The von Bertalanffy function was used to model the observed length-at-age data as Lt = 526.8 {1 exp[-0.141 (t 0.491)]} for males, and Lt = 618.2 {1 exp[-0.106(t 0.315)]} for females. Females grew at a slower rate but attained a larger size 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. http://zoolstud.sinica.edu.tw/Journals/51.2/185.pdf