|Scientific Name:||Acipenser dabryanus|
|Species Authority:||Duméril, 1869|
|Red List Category & Criteria:||Critically Endangered A2bcd ver 3.1|
|Reviewer/s:||Pourkazemi, M., Zhang, H., Du, H. & Smith, K.|
This species is endemic to China and is restricted to the Yangtze River system. It has recently been extirpated from the lower reaches of river and is now restricted to the upper main stream in the Sichuan Province. It also enters major tributaries, including the Ming, Tuo, and Jialing rivers. In the late 20th century population numbers declined drastically due to overfishing and habitat degradation. Incidental catch data between 1982 and 2008 indicate that since 1982 only tens of specimens are being captured annually. Artificial propagation began in 1976 by the Chongqing Fisheries Institute, China. Since 2007, more than 5,000 individuals have been released into the upper reaches of the Yangtze River for stock rehabilitation (Zhang et al. 2009). Dam construction has caused major adverse effects to the habitat of this species and have resulted in a reduction in its area of occurrence of this species. The naturally occurring population is considered to be very small and it is thought this species only survives in the wild due to restocking. No evidence exists to show that re-stocked animals are reproducing in the wild. Therefore, due to inferred and suspected population declines, along with a decrease in the area of occupancy and historical overfishing, this species has been assessed as Critically Endangered (Possibly Extinct).
|Range Description:||This species is endemic to China and is restricted to the Yangtze River system. Historically, under the natural, unaltered conditions that existed until the middle of the 20th century, this species inhabited the upper and middle reaches of the Yangtze River and its large tributaries, including the Ming, Tuo, Jialing, Xiang and Han rivers, as well as the large lakes linking attached to the Yangtze River.
A. dabryanus has recently (possibly since 1995) been extirpated from the lower river and is restricted to the upper main stream of the Yangtze River in the Sichuan Province. It also enters major tributaries, including the Ming, Tuo, and Jialing rivers. (Zhuang et al. 1997).
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||The natural population of this species was not considered to be large. Historically, this was an important species in commercial fisheries of the upper reaches of the Yangtze River (Chen 2007). In the late 20th century population numbers declined drastically because of overfishing and habitat degradation. Incidental catch data between 1982 and 2008 indicate that since 1982 only tens of specimens are being captured annually and there have been no capture records below the Gezhouba Dam since 1995. The stock has dropped markedly during the past 20 to 30 years and now the production is so small and scattered, that no exact account of total production is reported. Artificial propagation began in 1976 by the Changjianq Fisheries Institute, China. Since 2007, more than 5,000 individuals have been released into the upper reaches of the Yangtze River for stock rehabilitation (Zhang et al. 2009).|
|Habitat and Ecology:||
This is a small sturgeon species that is permanently resident in freshwater. It usually inhabits the middle and lower layers of the water and prefers slow moving water that is rich in humus, and feeds on demersal organisms (those that live at or near the bottom of a body of water).
This species spawns in upper reaches of the Yangtze River, in the spring (March-April) and the autumn (October-December). Its key spawning reach is between Maoshui and Heijang, a stretch of 321.7 km (The Chanjiang Aquatic Resources Survey Group 1988).
This species has historically experienced unsustainable levels of fishing. Furthermore, mesh sizes of fishing nets have reduced, thereby capturing young, especially during the periods when many juveniles concentrate to feed.
Fishing effort and intensity has also increased in the past, for example in the Neijiang reach of the Tuo River there were only 500 fishing boats in 1950s, but this number increased to about 2000 by 1985. In the Leshan Reach of the Ming River, drift gill nets are crowded together from day to night.
The primary traditional fishing season in the main stream of Yangzte River is between March and August, with more than 30% of the catch processed between April and May. However, this is also spawning season of A. dabryanus, therefore spawning stock are particularly vulnerable to capture.
Furthermore, the construction of the Gezhouba Dam in 1981 and the Three Gorges Dam in 2003 have caused major adverse effects to the habitat of this species and have resulted in a reduction in the area of occurrence of this species, which is now restricted to the upstream river, above the dams. More recently, the construction of the Xiangjiaba Dam in 2008 is situated in the middle of this species spawning reach and therefore is expected to adversely affect the population through habitat fragmentation and associated habitat degradation.
Additionally pollution from increasing human development affects the entire Yangtze basin. Much untreated waste water discharges into the river each year. Water quality is also affected by run-off caused by deforestation of the the upper Yangtze Valley (Zhuang et al. 1997).
A three month seasonal fishing ban between February and April was introduced in 2002 in the upper Yangtze River.
This species has been listed as a First Class Protected Animal of the State since 1988, and has received the same effective protection as Acipenser sinensis. This species was also listed on CITES Appendix II in 1998.
Artificial propagation was first carried out in 1976. Since 2007 more than 5000 juveniles have been released into the upper Yangtze River for stock rehabilitation, but these species are not thought to be breeding in the wild and no larvae have been seen in recent years.
It is considered that the survival of this species is entirely reliant on restocking efforts, without which this species would possibly become extinct (Zhang et al. 2009).
Since the 1970s, the Institute of Aquatic Products of Sichuan Province have increased efforts regarding raising and breeding of A. dabryanus. For example young A. dabryanus from the Yangtze River have been introduced into the Changshou City reservoir for culturing (The Changjiang Aquatic Resources Survey Group 1988).
In 2000 the first national nature reserve was created in the upper Yangzte river. The area of this reserve was extended in 2005 to mitigate the conflict between hydroelectric projects and the maintenance of the functionality of the ecosystem. The reserve is now the largest aquatic reserve in China, which has a total length of 1162.6 km (including 436.5 km of the main river) (Zhang et al. 2009).
|Citation:||Qiwei, W. 2010. Acipenser dabryanus. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2. <www.iucnredlist.org>. Downloaded on 12 March 2014.|
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