Vijayan said that the State Pollution Control Board (PCB) conducted an inspection of the river following the incident and the water samples tested showed dissolved oxygen to be below the levels required for fish to survive.
Kerala Chief Minister Pinarayi Vijayan on Tuesday said in the assembly that the recent mass death of fish in the Periyar river resulted due to less dissolved oxygen in the water and there was no discharge of chemical waste from factories into the river.
The chief minister made the submission in response to a query by opposition UDF MLA T J Vinod with regard to action taken against those who allegedly discharged chemical waste into the river resulting in the death of the fish.
Vijayan said that the State Pollution Control Board (PCB) conducted an inspection of the river following the incident and the water samples tested showed dissolved oxygen to be below the levels required for fish to survive.
"According to the preliminary investigation, when the shutter of the Pathalam regulator-cum-bridge was opened following heavy rains, a large amount of oxygen-poor water flowed into the river from the upstream side of the regulator," the CM said.
The initial probe also did not find any discharge of chemical waste into the river from the factories on the shores of the Periyar, he said.
The CM further said that the PCB will submit its detailed findings only after getting the report of the Kerala University of Fisheries and Ocean Studies (KUFOS) on the issue.
Regarding the loss suffered by fish farmers, Vijayan said that preliminary data indicates that it was to the tune of Rs 13.56 crore.
Once recommendations are received regarding the compensation to be given to the fish farmers, they will be examined and appropriate action will be taken, he said in the House.
Fish were found dead in large numbers in fish farms across panchayats adjoining Periyar such as Varapuzha, Kadamakkudy, and Cheranalloor in Ernakulam district on May 21.
Subsequently, the state government had held a meeting and worked out long and short term measures to prevent a recurrence of the incident.
The short term preventive measures included formulating protocols for opening the Pathalam regulator-cum-bridge on Periyar river and installation of biofilters on industrial units on the river's banks.
The long term measures were with regard to protecting and reclaiming the Periyar as well as other rivers in the state and included taking steps to set up a river-related authority, state Industries Minister P Rajeev said last month.