Approximately 250 tons of farmed clams died recently across an 80-hectare area on the alluvial flats near the Mai Lam village estuary in Mai Phu commune, Ha Tinh province (formerly part of Loc Ha district). This incident, occurring nearly two weeks ago in late April, has caused economic losses amounting to billions of dong for 43 farming households.

According to the Ha Tinh Provincial Fisheries Sub-Department, the primary causes for the mass clam deaths were erratic transitional weather and excessively high stocking densities. The weather shifted abruptly from intense heat to heavy rain, causing sudden temperature changes that significantly impacted the clam habitat.

Clam shells accumulated in white streaks as the tide receded. Photo: Duc Hung

Adding to the environmental stress, many farming grounds in Mai Lam village have been used for extended periods, with continuous stocking over multiple seasons without adequate breaks for rehabilitation or cleaning. Common stocking densities in these areas range from 800 to 1,000 clams per square meter, which is three to seven times higher than expert recommendations. This practice increases the risk of disease outbreaks, leading to weakened clams and mass mortalities.

Analysis of samples indicated that the clam deaths were not related to common mollusk pathogens like Perkinsus olseni and Perkinsus marinus, which are single-celled parasites that can weaken and kill clams under unfavorable conditions. Additionally, experts did not detect toxic algae in the water environment, further pointing to environmental factors and management practices as the main culprits.

Clams died en masse in Mai Phu commune's pond in late April. Video: Duc Hung

In response to the losses, pond owners have hired seasonal workers, paying 500,000 dong per day to collect dead clams and shells from the mud. This effort aims to clean the farming ponds and minimize adverse effects on the surviving clams.

Commercial clams from Ha Tinh are primarily purchased by traders and supplied to wholesale markets and restaurants both within and outside the province, supporting the seafood business. A portion of the output is sent to processing facilities for freezing or drying, enabling longer-term consumption. Currently, the price of clams is around 23-24 million dong per ton.

Duc Hung