Yangtze River Demersal Habitat
This taxon is one of a number of demersal species in the Yangtze River system. Demersal river fish are found at the river bottom, feeding on benthos and zooplankton.
The upper Yangtze basin consists chiefly of Paleozoic limestone and terrigenous sedimentary rock, with some granitic material. The most downstream element of the upper Yangtze basin is often termed the Sichuan Basin; here the Yangtze cuts through Triassic and Permian material before entering the Three Gorges. The Three Gorges area is a stretch of the Yangtze that runs approximately 660 kilometers, terminating at the site of the Three Gorges Dam. Prior to construction of the dam, the Three Gorges area was a site of exceptional natural beauty; after dam construction the gorge areas were filled with approximately 100 meters in depth of Yangtze water, and considerable amounts of the watershed were graded.
The lower Yangtze basin consists of anabranching river structures and Pleistocene coastal terraces. Prior to development of the Three Gorges Dam, the Yangtze Delta was replenished with a copious sediment load reaching the river mouth; however, the dam has now severely limited the natural flow and deposition of sediment to the delta region. Consequently, the integrity of the delta is been compromised, with scouring exceeding deposition, and the very stability of the delta is endangered.
Lower and middle basins of the Yangtze carry heavy pollutant loads. In the lower Yangtze basin nitrate levels are high, measuring at about 1000 tons per day at Datong; these levels accrue from high applications of chemical fertilizer applied and also considerable loadings of untreated sewage due to the large human population of the basin, with correspondingly little infrastructure for sewage treatment.
Heavy metal concentrations are also high in the lower Yangtze, with measurements of dissolved lead at 0.078 microgram/liter; cadmium (0.024 microgram/liter), chromium (0.57 microgram/liter), copper (1.9 microgram/liter), and nickel (0.50 microgram/liter). Levels of dissolved arsenic have been measured at 3.3 microgram/liter) and zinc at 1.5 microgram/liter), both notably higher by factors of 5.5 and 2.5 respectively than other typical large world rivers. In Yangtze River suspended sediment, arsenic comprises 31 microgram/gram, lead comprises 83 microgram/gram, and nickel comprises 52 micrograms/gram of sediment content
There are several large native demersal fish found in the Yangtze River, chiefly the 250 centimeter (cm) long endangered Yangtze sturgeon (Acipenser dabryanus), the 120 cm Chinese sturgeon (Acipenser sinensis), the 200 cm Giant mottled eel (Anguilla marmorata), the 122 cm black carp (Mylopharyngodon piceus), the 300 cm Chinese paddlefish (Psephurus gladius), and the 100 cm Silurus meridionalis. Furthermore, there are a few exceptionally large native benthopelagic fishes found in the Yangtze, namely, the 105 cm Silver carp (Hypophthalmichthys molitrix), the 200 cm Wuchang bream (Megalobrama amblycephala), the 200 cm yellowcheek (Elopichthys bambusa), the 145 cm common carp (Cyprinus carpio carpio), the 122 cm Mongolian redfin (Chanodichthys mongolicus), the 102 cm predatory carp (Chanodichthys erythropterus) and the 100 cm snakehead (Channa argus argus).. The demersal fish Silurus meridionalis also is found as a Yangtze River endemic species.
Habitat and Ecology
Adults reach the middle sections of the river in September or October, where they overwinter. Ripe individuals were formerly found as far inland as the Jingsha River during the following October and November, where they spawned. Prior to construction of the Gezhouba Dam, the migration distance was as long as 2,500 to 3,300 km. Spawning sites often occur in turbulent sections of the river with rocky substrate and steep cliffs on both banks.
The roe is very large and it sinks and sticks to gravel until hatching. The hatched fries descend from the river to sea near the coast where they grow. They feed mainly on zoobenthos and other bottom invertebrates.
Juvenile A. sinensis of 7 to 38 cm tail length occur in the Yangtze River estuary from the middle of April through early October. These are presumably one-year-old individuals. Juveniles weighing a few kilograms can be found in coastal waters near the river mouth. Individuals from 25 to 250 kg in weight were registered in some fishing grounds of East China Sea and Yellow Sea. This species attains a length of more than 3 metres.
Molecular Biology and Genetics
Barcode data: Acipenser sinensis
Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.
See the BOLD taxonomy browser for more complete information about this specimen and other sequences.
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Download FASTA File
Statistics of barcoding coverage: Acipenser sinensis
Public Records: 2
Specimens with Barcodes: 3
Species With Barcodes: 1
IUCN Red List Assessment
Red List Category
Red List Criteria
- 1996Endangered (EN)
In the 1970s, the total spawning population of this species was estimated at 10,000 individuals. In 1981, the construction of the Gezhouba dam isolated the upper reaches of the Yangtze river. In 1983 and 1984, the mean spawning stock size was estimated at 2,176 individuals (946 and 4,169 as 95% confidence intervals). Available data from acoustic surveys show that between 2005 and 2007, the total spawning stock of Chinese Sturgeon was 203-257. This data indicates a 97.5% reduction in the total spawning population over a 37 year period.
During 1996-2001, studies using tag-recapture methods, population structure analysis and sonar counting indicated that the spawning stock in the Yichang spawning area (mid-lower reaches of the Yangtze river) had decreased since the completion of the Gezhouba Dam. Annual estimates of spawning adults within the 40 km (including the 4km long spawning area) ranged from 199 to 473 (Chang 1999, Wei 2003).
Between 1983 and 2007, more than 9 million juveniles were released into Yangtze River to increase wild stocks. Prior to 1996, only the larvae were released as techniques had not been developed to cultivate fry, so survivability is expected to be very low (Wei 200, Chen 2008). After 1999, improvement in hatchery techniques allowed juveniles to be raised and the released, but the contribution to wild stocks is considered to be less than 10% (Wei 2003, Zhu 2003).
Habitat fragmentation, alteration, destruction and changes to hydrological conditions also significantly impacts this species. The construction of the Gezhouba dam in 1981 blocked the migration routes of this species, making it impossible for it to reach spawning sites in the upper reaches of the river. Currently, there is just one remaining spawning ground, which is situated below the Gezhouba dam.
In 2003, the Three Gorges dam was constructed 40 km upstream of the Gezhouba dam. This has changed the hydrological regime (lowering the water level of the river in autumn and winter) and affected the water temperature.
Additionally, an increase in the amount of shipping traffic in the Yangtze river could be detrimental to the Chinese Sturgeon.
New evidence shows that water pollution is a potential factor lead to the decline of Chinese Sturgeon. Synthetic chemicals in water could contribute to the population decline of this species by significantly decreasing both the quality and quantity of eggs and spawning frequency of fish (Hu 2009).
Commercial fishing has been closed since 1983, and now just small numbers (less than 40 individuals in recent years) are caught for scientific or propagation purposes.
In 1988, A. sinensis was listed a Class I State protected animal. In 1996, Yichang Chinese Sturgeon Nature Reserve was established, protecting the spawning population. In 2002, a Chinese Sturgeon Nature Reserve in the Yangtze River estuary was established to protect juvenile sturgeons gathering there. This species was listed on CITES Appendix II in 1998.
In 1983, the Yangtze River Fisheries Institute artificially spawned this species (Fu et al. 1985). From 1983 to 2007, more than 9 million Chinese Sturgeon (including larvae) were released into Yangtze River to increase the stock (Xiao et al. 1999, Chen 2007).
Currently, adult sturgeons are captured on spawning ground to be used for artificial breeding . Efforts are being made to rear and breed this species in captivity so that captive adults can be used for stocking in the future.
Relevance to Humans and Ecosystems
The Chinese sturgeon (Acipenser sinensis; Chinese: 中华鲟; pinyin: zhōnghuá xún) is critically endangered member of the family Acipenseridae in the order Acipenseriformes. Historically, this anadromous fish was found in China, Japan, and the Korean Peninsula, but it has been extirpated from most regions due to habitat loss and overfishing.
It is strictly protected by the Chinese government, named a "national treasure" much like its mammalian counterpart, the giant panda. China has several conservation programmes, including reserves specifically aimed at this species and restocking through release of juveniles in the Yangtze River.
Sturgeon are comparatively basal species of fish, which date back to the Cretaceous period. Scientists believe it is a transitional species of cartilaginous fish and bony fish, and is also regarded as a kind of Ganoidei with cartilage. The fish is marked by multiple blocks of osteons.
Chinese sturgeon can range between 200 and 500 cm (79 and 197 in) in body length, and weigh 200 to 500 kg (440 to 1,100 lb) on average. It is believed an adult sturgeon can reach up to 5 m (16 ft) in length, and weigh over 450 kg (990 lb), ranking among the largest sturgeon in the world. Its head is acuminate, with the mouth under its jaw.
Most sturgeon spawn in fresh water and migrate to salt water to mature. The Chinese sturgeon can be considered a large freshwater fish, although it spends part of its lifecycle in seawater, like the salmon, except Chinese sturgeon spawn multiple times throughout their lives.
The Chinese sturgeon has a habit of upstream migration; it dwells along the coasts of China's eastern areas and migrates back up rivers for propagation upon reaching sexual maturity. It has the longest migration of any sturgeon in the world, and once migrated more than 3,200 km (2,000 mi) up the Yangtze. The sturgeon's reproductive capacity is poor; it may breed three or four times during its life, and a female sturgeon can carry in excess of a million eggs in one cycle, which are released for external fertilisation when mature. The survival rate to hatching is estimated to be less than 1%.
The Chinese sturgeon is a critically endangered species native to China. It is largely dispersed over the main streams of the Yangtze River and coastal regions of Qiantang River, Minjiang River, and Pearl River. Most aquatic animals are food for the young of the Chinese sturgeon, while the adults feed on aquatic insects, larvae, diatoms, and humic substances.
In the 1970s, an estimated 2,000 Chinese sturgeon spawned in the Yangtze River every year. Now, that number is down to several hundred due to the threats to its habitat, such as pollution and other human action. The channel for adult fish migrating to traditional spawning sites such as the Jinsha River in the upstream of Yangtze River was blocked after the construction of the Gezhouba Dam hydroelectric power project in the early 1980s.
The sturgeon is also highly sensitive to increased noise on the river caused by growing river traffic, as well as being vulnerable to death or injury by boat propellers.
Protection and research
The primitiveness of the Chinese sturgeon makes it a great academic interest in taxonomy and biology. For this reason, China has been studying ways to breed and preserve the endangered species, classified as "China's Class One Protected Animals" since the 1970s.
Built in 1982, the Chinese Sturgeon Museum is part of the Chinese Sturgeon Institution of China which is using artificial breeding techniques to try to preserve this endangered species. The museum is located on a small island called Xiaoxita in the Huangbo River, within Yiling District of Yichang.
The Yangtze River Fisheries Research Institute of the Chinese Academy of Fisheries Sciences in Jingzhou is one agency charged with breeding sturgeon in captivity for restoring the river population before the species disappears.
Some success has been claimed by the authorities from artificial inducement for spawning and stream discharge for incubation. On 29 April 2005, to mark the 20th anniversary of the China's efforts to protect the species, over 10,000 sturgeon fry, 200 junior sturgeon, and two adult fish were released into the Yangtze River at Yichang. During the course of the project, 5 million fish bred in captivity have been released into the wild. However, in 2007, 14 young sturgeon were surveyed near the mouth of Yangtze compared with 600 the year before, causing concern that effort was a losing battle in the crowded and polluted Yangtze river.
To mark China's hosting the Olympic Games, the Chinese Central Government made a gift of five sturgeon, symbolising the five Olympic rings to Hong Kong. The fish made their debut in Ocean Park Hong Kong on 20 June 2008. One of the fish, however, died by January 2009 due to unknown causes.
- Qiwei, W. (2010). "Acipenser sinensis". IUCN Red List of Threatened Species. Version 2012.2. International Union for Conservation of Nature. Retrieved 24 February 2013.
- ""Living fossil of fish" Chinese sturgeons debut in HK". Xinhua. 20 June 2008.
- "Chinese sturgeon". Chinese Ministry of Culture. Retrieved 15 July 2008.
- Dwayne Meadows, Heather Coll (October 2013). "Status Review Report of Five Foreign Sturgeon". Report to Office of Protected Resources. National Marine Fisheries Service. p. 78. Retrieved November 29, 2014.
- Elaine WU (15 July 2008). "At home in saltwater and fresh". South China Morning Post (Hong Kong).
- Stefan Lovgren (15 August 2007). ""Living Fossil" Fish Making Last Stand in China". National Geographic. Retrieved 15 July 2008.
- "Chinese Sturgeon Set Free". China.org.cn. 29 April 2005. Retrieved 15 July 2008.
- Chinese Sturgeon Museum
- "Scientists sound alarm as Chinese sturgeon battle for survival". AFP. 23 July 2007. Retrieved 15 July 2008.[dead link]
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