| Acipenser dabryanus | |
|---|---|
| Conservation status | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Actinopterygii |
| Order: | Acipenseriformes |
| Family: | Acipenseridae |
| Genus: | Acipenser |
| Species: | A. dabryanus |
| Binomial name | |
| Acipenser dabryanus Duméril, 1869 |
|
The Yangtze Sturgeon (Acipenser dabryanus), also known as Dabry's Sturgeon, is a member of the family Acipenseridae and the order Acipenseriformes.
It is thought to have lived at the same time as dinosaurs, dating back to a period 140 million years ago. Because of that, it is sometimes also known as a living fossil. It is an animal strictly protected by the Chinese government, named a "national treasure" much like its mammalian counterpart, the Giant Panda.
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The sturgeon is a comparatively basal species of fish, which date back to the Cretaceous period.[2] 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.[3]
Specimens can range between 200 to 500 cm (79 to 200 in) in body length, and weigh 200 to 500 kg (440 to 1,100 lb) on average. A grown-up sturgeon measures up to 4 metres (13 ft) long, and weighs over 450 kg (990 lb), ranking the third biggest only to the White sturgeon and Atlantic sturgeon. Its head is acuminate, with the mouth under its jaw.[3]
Sturgeon are anadromous meaning they spawn in fresh water and migrate to salt water to mature.
The Chinese variety can be considered a large fresh water fish, although it spend part of its life-cycle in seawater, like the salmon.[4]
The Yangtze Sturgeon has a habit of upstream migration: they dwell along the coasts of China's eastern areas and migrate 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.[5] The sturgeon's reproductive capacity is poor: it may breed three or four times during its life-cycle, and a female sturgeon can carry in excess of a million eggs in one pregnancy, which are released for external fertilisation when mature. The survival rate to hatching is however estimated to be less than 1 percent.[4]
The Yangtze sturgeon is a precious but 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.[3] Most aquatic animals are food for the young of the Chinese Sturgeon, while the adults feed on aquatic insects, larval, diatom and humic substances.[3]
In the 1970s, there were an estimated 2,000 spawning Chinese sturgeons in the Yangtze River every year. Now that number is down to several hundred due to the threats to its habitat, such as pollution[6] 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 hydro-electric power project in the early 1980s.[5]
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.[5]
The primitiveness of the Yangtze 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 1970s.[2]
Built in 1982, the Chinese Sturgeon Museum is part of the Yangtze Sturgeon Institution of China which is using such 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.[7]
The Yangtze River Fisheries Research Institute of the Chinese Academy of Fisheries Sciences in Jingzhou is one agency charged with breeding sturgeons in captivity for restoring the river population before the species disappears.[5]
Some success has been claimed by the authorities from artificial inducement for spawning and stream discharge for incubation.[3] In 29 April 2005, to mark the twentieth 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.[6] 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.[8]
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.[2] One of the fish, however, died by January 2009 due to unknown causes.