Stock assessment and management implications of an endemic fish, , in the Yarlung Zangbo River in Tibet, China.

Background: is an endemic species only inhabiting the middle and upper reaches of the Yarlung Zangbo River and its tributaries at altitudes above 3600 m in the Qinghai-Tibet Plateau and has suffered a continuous decline of population size owing to anthropogenic disturbance. However, little is known about the stock status of this species and how to protect it. In this study, we evaluated the population status of and investigated two management policies including the minimum age limits and seasonal closure in the Yarlung Zangbo River.

Results: Estimates of the total mortality rate were 0.35 year for females and 0.65 year for males. The natural mortality rates were estimated as 0.10 and 0.22 year for females and 0.12 and 0.29 year for males using two empirical methods. The population may be in near full exploitation under the current harvesting strategy in the Yarlung Zangbo River, with a high chance of recruitment failure in the future. Although both minimum age limits and seasonal closure could be effective measures to conserve the stock, it was proposed that aseasonal closure was implemented each year from September to December according to the complexity of the application and the effects on the income of local fishermen and on the biological invasion.

Conclusions: The stock of may bein near full exploitation under the current harvesting strategy, with a high chance of recruitment failure in the future. Our results indicated that the imposition of the seasonal closure from September to December might be the effective measure to conserve the population.