Friday, May 2, 2008

Exotic fish threatening Vietnam’s ecosystems

Several non-native fish species brought into Vietnam in recent years could displace native species and damage ecosystems unless prompt action is taken, scientists have warned.
Fishermen on the Saigon River in Ho Chi Minh City have recently been catching large amounts of suckermouth catfish (Hypostonuns lecostomus) – an imported fish that used to be bred as pets.
Nguyen Van Chuc, a resident in the city’s Binh Thanh District, said he could catch up to 100 of the fish daily.
“The fish have been reproducing rapidly and I can now catch them everywhere,” said Chuc.
Nguyen Tuan, an expert from the Research Institute for Aquaculture No. 2, said suckermouth catfish eat indiscriminately and reproduce rapidly.
“To compete for food, the fish invade the environments of other species and damages them,” he said.
The suckermouth has also appeared in rivers in the Mekong Delta in recent years.
Two other carnivorous fish species, the Colosoma brachpomum and Cichla ocellaris, are threatening the ecology of the Tri An Reservoir in the southeastern province of Dong Nai, according to local scientists.
Farmers originally brought in the two fish species, which are native to tropical areas of the Amazon River and reproduce rapidly, and bred them in the reservoir.
In addition, the Yabby (Cherax destructor), a species of crayfish from Australia, was recently imported and bred by local farmers in the central province of Phu Yen.
The yabby is threatening irrigation works in the area because of its habit of burrowing into levee banks and dam walls, said Tuan.
“If farmers let the yabby get out of captivity, they can cause considerable damage to dams around the river,” he warned.
Nguyen Dang Nghia, director of the Agriculture Technology Transfer Center, said authorities have been lax about controlling the entry of non-native species into the country without carefully researching their impact on the local ecosystems.
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