Alien fish are threatening local fish systems in the Pearl River in south China.

Director of the Guangzhou Fishery Management Bureau Zou Rongya said the invasion of exotic fish is threatening the local aquatic system.

The Qingdaofu, or siluraformes, was identified recently as a particularly serious threat, Zou said.

Fishermen and clean-up workers have recently discovered a large number of these fish in the Bai'etang-Huangpu Port section of the Pearl River.

"Eight out of the 10 fish we catch in the Pearl River now are Qingdaofu," said one fisherman.

The fish, which look like angelfish, have eaten many small fish and have started rapidly producing their own fry.

"Its fast growth has seriously threatened other species' reproduction, leading to an unbalanced aquatic eco-system," Zou said.

The grey and white fish can grow 20-30 centimeters long and weigh about 1 kilogram, Zou said.

One fisherman in Guangzhou first caught a Qingdaofu in early 2003, when nobody could name it.

Probably originating in Latin America, the fish became a popular pet because of its strange appearance.

The fish is also found in Taiwan Province, where workers have tried several methods to deal with it but in vain, Zou said.

The species is one of the most aggressive to invade the river.

"Invasive fish species have changed the local aquatic system by modifying species composition, population structure and food chains," Zou said.

No effective methods have been found to eliminate it. All Zou could suggest was that fishermen did not throw it back if they caught it by mistake.

(China Daily June 18, 2005)