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Vol. 54, 2015
Stock assessment and management implications of an endemic
fish, Oxygymnocypris stewartii, in the Yarlung Zangbo
River in Tibet, China
Bin
Huo1, Bao Shan Ma2,
Cong Xin Xie1*, You Jian
Duan1, Xue Feng Yang1
and Hai Ping Huang1
1College
of Fisheries, Huazhong Agricultural University, Wuhan, Hubei 430070,
China
2Yangtze River Fisheries Research Institute, Chinese
Academy of Fishery Sciences, Wuhan, Hubei 430223, China
Abstract
Background: Oxygymnocypris stewartii 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 O. stewartii 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−1 for females and
0.65 year−1 for males. The natural mortality rates
were estimated as 0.10 and 0.22 year−1 for females and 0.12 and 0.29 year−1 for males using two empirical methods.
The O. stewartii 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 O. stewartii stock, it was proposed
that a seasonal 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 O. stewartii may be in 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 O.
stewartii population.
Key words: Oxygymnocypris
stewartii; Per-recruit;
Seasonal closure; Mortality; Conservation.
*Correspondence: E-mail: xiecongxin@mail.hzau.edu.cn
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