Changes to the water environment on the La Nga river in the southern Vietnamese province of Dong Nai have been blamed for the death of nearly 1,000 tonnes of fish this month, provincial officials have said.
Vice-chairman of Dong Nai Province People’s Committee Vo Van Chanh said on Monday that as soon as the mass death of fish on the river in the province’s La Nga and Phu Ngoc communes was reported, the Southern Environment Observation Centre, Zone VI Animal Health Department and the province’s Environment Department took water samples.
Test results showed the concentrations of ammonia, nitrite and the chemical oxygen demand (COD) in samples were in excess of levels allowed in aquaculture farming, Chanh said.
Director of the province’s Agriculture and Rural Development Department Huynh Thanh Vinh said rain lasting from May 15 to early morning of May 16 made waste flow into the river, lowering the dissolved oxygen content in the river’s surface water, killing the fish.
The concentration of ammonia in water river samples was four to seven times higher than allowed, the nitrite concentration two to three times higher than permitted and the COD concentration three to 16 times higher than permitted.
Moreover, testers found no signs of common diseases or infectious diseases that freshwater fish tend to contract.
According to the department, last June, more than 1,900 tonnes of fish from 132 local households were found dead along the five kilometre portion of the river after heavy downpours.
The low oxygen level in the water and the high density of fish were reported as the main cause of the mass deaths at that time.
As of last December, the provincial People’s Committee had spent more than 12 billion dong ($516,000) to support affected households in Phu Ngoc and La Nga communes.
Nguyen Van Khoai, a fish farmer in Phu Ngoc commune, said breeding fish on the river had been his family’s livelihood for 14 years but in the last two years, he lost hundreds of millions of dong and was in debt because of the mass fish deaths.
“After last year’s mass fish deaths, I borrowed more than 100 million dong to buy breeding fish to resume farming. Now, I owe 300 million dong more for buying feed for the fish,” Khoai said.
He said he had to sell all the fish cages that his family had to cover the debt but it was not enough.
“After handing the fish cages to the buyer, we’ll go onshore, rent a house and seek a job,” Khoai said.
Vinh said the department planned to help fish farming households who were affected by the recent mass fish deaths.
Deputy Prime Minister Truong Hoa Bình on Tuesday asked for further investigation into the cause of the mass deaths of fish and hand out appropriate punishments to those who violated the law.
Binh also ordered Dong Nai authorities to review the major sources of waste discharged into the river, particularly giving focus to the cases that received complaints from the public.
A thorough report is expected to be submitted to the prime minister before June 30. VIET NAM NEWS/ASIA NEWS NETWORK