The Fisheries Department has instructed fish farm owners in Vedaranyam-Keezhavelur block to stop culturing prawns in brackish water upstream of check dams under construction across the Adapparu and the Harischandra rivers.
The check dams are being constructed to harness fresh water for agricultural purpose.
The department has permitted culturing of prawns only in fresh water ponds in areas upstream of check dams.
Prawn farm owners who do not heed to the instruction will face action, Collector S. Suresh Kumar said. The administration is keen to ensure that the prawn farms do not obstruct draining of rainwater into sea at the time of floods.
According to local residents, there are hundreds of ponds upstream of check dams where prawns are cultured in brackish water pumped from the sea through inlets. Over the last decade, several hundreds of agricultural lands have been converted into shrimp farms much to the detriment of farmers.
The instruction has come as a breather to farmers. But, the concern about productivity of crops remains, Ravichandran, an agriculturist of Thalaignayiru, said.
Since saline water that is pumped into farms is mixed with medicines to protect shrimps from diseases, seepage causes contamination. Salinity of top soil is irreversible and cannot be used for agriculture once shrimp culture season is over, farmers said.
The gradual rise in salinity in soil has become noticeable in lands from Thalaignayiru to Vettiakaran Iruppu, and Umbalacheri to Avarikadu, farmers said.