The Chinese sturgeon, listed among the country's most endangered species, has been forced to change its eating habits due to the deterioration of water quality in the Yangtze River, researchers said yesterday after completing a one-year study.

The Chinese sturgeon is an endangered species under the highest level of state protection. Having evolved over millions of years, it is regarded as a living fossil by some marine biologists.

Now scientists only know that as a migratory fish, Chinese sturgeons lay eggs in the upper reaches of the Yangtze River. The young sturgeon swim thousands of kilometers to reach the sea.

"We know very little about their movement in the mouth of the river due to lack of research, let alone their habits in the sea," said Liu Jian, deputy director of the administration of the Shanghai Yangtze Estuarine Preserve for Chinese Sturgeon.

As a result, fishery experts monitored a 276-square-kilometer preserve near Chongming Island and nearby waters to study the fish's habits and movement.

"The investigation found the main food for the Chinese sturgeon is now water earthworms," said Zhuang Ping, deputy director of the East China Sea Fisheries Research Institute.

Two decades ago Chinese sturgeon could find abundant bottom dwellers such as clams to eat.
"Metal pollution in the Yangtze River decreased the number of bottom feeders, forcing the Chinese sturgeon to find another source of food," Zhuang said. "It's hard to tell whether the change is good or not. But it indicates at least the fish is trying to adapt to the environment."

In addition, the investigation also makes it clear that babies of the Chinese sturgeon gather at the mouth of the Yangtze River from May to August every year with a peak in June.

Based on this, the government enacted an administrative regulation for the preserve in April, banning any artificial activities in the preserve from May 1 to September 30 each year.

Anyone fishing in the preserve during the period will be given a maximum fine of 10,000 yuan (US$1,205).

(Shanghai Daily June 29, 2005)