These cruel, carnivorous species of fish originated from South Africa. The escaped from some fish cages of local farmers to the reservoir.

According to the Dong Nai Fisheries Department, in 1995 a farmer in Ma Da commune, Vinh Cuu district, Dong Nai province bought five couples of ca hoang de from an ornamental fish shop to breed in his fish cage located on the Tri An reservoir. Each time he produced around 1,000 breeding ca hoang de to sell to other fish breeders. In 2002, when this species of fish was no longer a favourite in the market, he stopped producing ca hoang de.

During this time he released some ca hoang de into the Tri An reservoir. A period of time after that, local fishermen caught some ca hoang de from their net in Tri An reservoir. In recent years the number of ca hoang de in the reservoir has been developing rapidly. The largest ca hoang de that local resident has caught recently is around 1kg in weight and 20cm in length.

According to scientists, this species of fish can eat any creatures that they catch when they are hungry. Ca hoang de also has a very fast reproduction speed, laying 2,000 to 3,000 eggs each time. They can reach a maximal length of up to 60cm. This kind of fish can make changes to the ecosystem where they live.

For ca chim trang, according to scientists, they can’t produce babies in Tri An reservoir so it is difficult for them to develop densely in the reservoir. Ca chim trang is also a carnivorous species, which can destroy the original ecosystem where they live. This species of fish also escaped from fish cages into the reservoir.

Besides the two above species of fish, Tri An reservoir also has ca lau kinh (cleaning fish), which is bred by ornamental fish breeders to clean up ornamental fish tanks. Though they are not carnivorous but other species of fish can’t live in the environment where ca lau kinh lives. Therefore, the appearance of this fish is also a risk for ecological imbalance in the reservoir.

All of the above species of fish are imported into Vietnam by ornamental fish breeders. The Dong Nai Fisheries Department has asked all related local agencies to strictly control imported fish and it is combining with scientists to seek measures to prevent the development of those species of fish.