Yangtze sturgeon (Acipenser dabryanus)
|Also known as:||Dabry’s sturgeon|
|Size||Length: 130 – 250 cm (2)|
|Weight||16 kg (2)|
The Yangtze sturgeon is classified as Critically Endangered (CR) on the IUCN Red List 2007 (1), and is listed on Appendix II of CITES (3).
A prehistoric-looking fish, the Yangtze sturgeon has a long and slender body covered with rough skin and bony plates. A pointed snout extends from the triangular head and two pairs of barbels hang from the lower jaw. The upper side of the body varies from dark yellow through brown to dark grey, and this fades to milky white on the underside (4). Juveniles have a black body and tail with a light grey line running from head to tail (5).
Endemic to the Yangtze River, China (1).
The Yangtze sturgeon is found in a variety of freshwater habitats, away from the riverbank in water eight to ten metres deep. Adults appear to prefer regions with a sandy silt bottom, and young stay in sandy shallows (4).
This nocturnal fish undertakes regular migrations, and after becoming sexually mature at seven to eight years old, it swims upstream during the spring floods each year to spawn. A large number of sticky eggs are produced, which adhere securely to stones on the riverbed (4). From hatching to around three weeks old, the tiny juveniles remain close to the river bottom, feeding on zooplankton and hiding from predators. Once they reach 10 to 11 weeks old, they are large enough to migrate downstream to join the adults (5). Older Yangtze sturgeon consume small fish and aquatic plants (4).
The Yangtze sturgeon is at risk from over-fishing, pollution, and habitat degradation and loss. An important factor in its decline was the construction of the Gezhouba Dam across the Yangtze River at Yichang in Hubei Province in 1981. As this prevented upstream migration necessary for spawning, the Yangtze sturgeon is now only found above the dam (2).
Conservation of this fish is now urgent, with emphasis needed on habitat protection, capture control and stock replenishment. This sturgeon species spawns earlier in life than most sturgeons, and therefore has aquaculture potential for caviar production. Controlled production of the Yangtze sturgeon could both reduce fishing levels and allow reintroductions of fish back into the river (2).
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- Barbels: fleshy projections near the mouth of some fish.
- Endemic: a species or taxonomic group that is only found in one particular country or geographic area.
- Plankton: aquatic organisms that drift with water movements; may be either phytoplankton (plants), or zooplankton (animals).
- Reintroduction: putting an animal or plant into an area where the species or sub-species previously lived but from which they are locally extinct - usually referring to projects aiming to re-establish self-perpetuating populations.
IUCN Red List (December, 2009)