Escaped fish put old species at risk

Hybrid sturgeon released along with the floodwater

Experts are conducting a field investigation to assess flood damage to the ecosystem of the middle and lower reaches of the China's longest river - the Yangtze - after nearly 10,000 tons of foreign and hybrid sturgeon washed out of a breeding facility in heavy water flows.

Scientists worry that the hybrid and foreign species may now interbreed with endangered purebred Chinese wild sturgeon in the river, whose numbers have declined to dangerously low levels. Only 100 are thought to remain in the Yangtze.

Wei Qiwei of the Chinese Academy of Fishery Sciences, one of the investigators, said purebred Chinese sturgeon could face a heightened threat of extinction as a result of interbreeding with the foreign and hybrid species over the coming months.

"Too many foreign and hybrid sturgeon that were once raised along the middle and lower reaches of Yangtze River and its branches have escaped to the wild after floodwater discharges in July," said Wei, who also serves as director of freshwater biodiversity conservation in the Yangtze River Fishery Supervision and Management Office of the Ministry of Agriculture. "The purebred Chinese sturgeon is now facing a serious threat."

Purebred Chinese sturgeon date to 140 million years ago. But they are now on the razor's edge of survival. The population of adult purebred Chinese sturgeons was estimated at about 100 at the end of last year, compared with 10,000 in the 1970s, according to a protection plan for the fish released by the State Forestry Administration.

To protect the ancient species, fishing was banned as early as 1983, and a downstream conservation area was built.

A survey conducted by the fishery office estimated that after a reservoir opened a sluice to release floodwater on July 19, more than 9,800 tons of foreign and hybrid sturgeon in the Changyang and Yidu regions of central China's Hubei province were killed or escaped to the wild in Poyang and Dongting lakes, and to the middle and lower reaches of the Yangtze, where wild purebred Chinese sturgeons are living.

Floodwaters washed away the net-pen facilities used to raise the non-native species, causing huge economic losses.

It was the first time in 18 years that the Geheyan Power Station had discharged water over successive days in response to heavy rainfall.

The Wuhan-based Changjiang Water Resources Commission of the water ministry has also launched and investigation and is reviewing the matter, said Deng Yongyong, an official in the commission's publicity department.

Zhang Huiyun, a woman in Baiyanao village who makes her living by fishing, said all her 14 net-pens were washed away, and more than 1,500 kilograms of fish were killed or escaped, resulting in heavy economic losses.

Local fishery departments said fishermen reported catching foreign and hybrid sturgeon between July 26 and Aug 2.