Reproductive biology of Schizothorax waltoni (cyprinidae: schizothoracinae) in the yarlung zangbo river in Tibet, China

The reproductive biology of Schizothorax waltoni (Cyprinidae: Schizothoracinae) was studied by examining 1,145 individuals collected between August 2008 and August 2009 in the Yarlung Zangbo River, Tibet. The population had a significantly higher proportion of females than males (χ2 test, p < 0.05). Using a logistic regression, it was determined that the standard lengths at 50 % maturity were 369 mm for males and 479 mm for females; the ages at 50 % maturity were 10.2 years for males and 13.5 years for females. Based on the monthly proportions of macroscopic gonadal maturity stages and monthly variations in the gonadosomatic index, S. waltoni spawned over a short period, from March to April with a peak in March According to the size distribution of oocytes, S. waltoni appeared to show a high degree of spawning synchronicity. The fecundity of S. waltoni increased linearly with the standard length, body weight and ovary weight, but had no significant correlation with age. The mean fecundity of 21693 and mean relative fecundity of 13.4 eggs per gram of fish body weight suggest that S. waltoni might be especially vulnerable to exploitation.