Pollution the prime suspect for mass fish deaths on Vietnam’s central coast

By Pham Huong, Vuong Anh   April 22, 2016 | 02:04 pm GMT+7
Pollution the prime suspect for mass fish deaths on Vietnam’s central coast
Fish deaths have caused anxiety among the locals. : Duc Hung

Masses of lifeless fish are continuing to wash up along the coast of central Vietnam, and experts are debating the mysterious cause of their deaths.

Dr. Vu Thanh Ca from the Vietnam Sea and Islands General Department said an incomplete statistical report showed that 30 mass fish deaths have occurred globally since the beginning of this year, mainly related to the marine environment.

For shallow seas, organic pollutants discharged from the shore are not diluted quickly, Ca said. If the sea water temperature rises, the decomposition of these organic matter will happen faster and the oxygen consumption will rise. In case the wind is not strong enough to create a disturbance on the water surface to generate more oxygen, lower depths will be depleted of this life-supporting component, killing the fish.

From April 14 to 18 when the dead fish started washing up in the north-central area, the weather was hot and not windy at sea.

“Therefore, the mass fish deaths may have been caused by the decomposition of polluted water discharged from the shore that caused oxygen levels to fall,” Ca said.

Doctor Nguyen Huu Dung from the Vietnam Association of Seafood Exporters and Producers said there is a high chance that the polluted water came from an industrial complex located in Vung Ang ward, Ha Tinh province.

“A toxic substance flowed into the sea then followed the currents to other areas,” Dung said, adding that this is the first time Vietnam has recorded such a large number of dead deep-sea fish washing up.

According to aquaculture expert Bui Quang Te, a polluted sea environment will normally make algae “bloom”, depleting oxygen levels in the water and killing the fish. Te, however, said that algae cannot grow along Vietnam's central coast, so it must mean pollution levels are seriously high. In 2001-2002, a “red tide” happened in the central provinces of Ninh Thuan and Binh Thuan which spread across an area 25km long and 5km, killing a huge amount of prawns and fish. Other areas experienced a similar phenomena afterwards.

Another expert on maritime resources said authorities should look for traces of cyanide in the dead fish. This poisonous substance is sometimes used in fishing to attack the fish’s nervous system, making them easier to catch. The Philippines has called on China to stop the use of this substance in fishing.

“In my experience, the fish living near rock chains and coral are very strong and I think only cyanide can kill them,” he said.

Experts have agreed that authorities need to analyze water samples from different depths and areas to identify the polluting substance. They should also check production facilities and civil centers on land that might be responsible for discharging toxic waste into the sea.

The mass fish deaths along the central provinces of Vietnam were first reported in fish cages placed at sea near Vung Ang ward at the beginning of April. Since then, thousands of saltwater and freshwater fish as well as fish raised in cages have died in the provinces of Ha Tinh, Quang Binh, Quang Tri and Thua Thien-Hue. Locals who live along the coast have collected tons of dead fish since then, some weighing up to 50kg.

The Ministry of Agriculture and Rural Development has said people should not use the dead fish for consumption or production. The ministry has also ordered local authorities to collect and dispose of the fish to reduce environmental pollution.

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