The introduction of biological species doesn't always benefit biodiversity but may threaten the natural survival of indigenous species, says Cao Wenxuan, an academician with the Aquatic Biology Institute of the Chinese Academy of Sciences.

Maintaining a balanced ecosystem was more important, Cao said.

An example of an introduced species becoming invasive occurred at Xingyun Lake in southwestern China's Yunnan Province when bullheads, a large-headed North American freshwater catfish of the carp genus, were brought to China in the 1970s.

The introduction caused numbers of indigenous carp to decrease sharply as both kinds of fish have familiar food chains, Cao said.

Due to a lack of natural prey or restraints, imported species usually can breed in large numbers in a very short period and destroy the ecological balance in China's lakes or rivers, according to Cao.

To prevent an invasion by such species eventually depended both on relevant legislation and improving public awareness, said Cao.

The man-eating piranha, for example, had been put on the banned list of imported aquatic species by Chinese customs.

Unsuitable pets, including ferocious man-eating fish, snakes and crocodiles, should not be released into the wild, Cao added.

To date, China has about 120 kinds of invasive biological species, including water hyacinths and American white moths.

(Xinhua News Agency January 17, 2003)