Age and Growth of a Long-Lived Fish Schizothorax o'connori in the Yarlung Tsangpo River, Tibet

In total, 1126 individuals of Schizothorax o'connori were sampled during Aug. 2008 to Aug. 2009, from the Yarlung Tsangpo River, Tibet, and 2 tributaries to estimate the age and growth by an otolith analysis. The standard length (SL) ranged 33-553 mm and the body weight (W) ranged 4.3-2982.6 g. The SL-W relationship was described as W = 2.034 x 10 -5 SL 2.940 for the combined sexes. Furthermore, relationships of otolith dimensions (length, breadth, thickness, and weight) and fish length/age were described. Otoliths continually grew in size with SL, but growth became asymmetrical over time. Otolith weight was the only variable which synchronously increased with age. The index of the average percentage for age estimation of 2 independent readers was 3.24%, and 3.3% of otolith sections were considered illegible. The maximum observed ages were 40 yr for males and 50 yr for females. The mean length-at-age had no significant difference between sexes up to age 8 yr, while females attained larger lengths-at-age than males thereafter. The von Bertalanffy function was used to model the observed length-at-age data as L t = 499.7 (1 - e -0.095 (t +896) ) for males and L t = 576 .9 (1 - e -0.081 (t+0.946) ) for females. Females grew at a slower rate but attained a larger size than males. http://zoolstud.sinica.edu.tw/Journals/49.6/749.pdf.