Varapuzha: A mass fish kill was reported early on Tuesday, suspected to be caused by the release of effluents from industries upriver in the Eloor-Edayar area of Ernakulam.

Hundreds of fish, worth lakhs of rupees, were found dead in the Periyar River and nearby water channels.

Fish farmers practising cage farming have suffered significant losses, amounting to lakhs of rupees. There are over 200 fish cages installed in these areas. The toxins flowed into these fish cages, resulting in the deaths of species such as Asian sea bass, pearlspot, and tilapia.

Farmers had invested between Rs. 5 lakhs and Rs. 20 lakhs in cage farming. This mass kill, occurring around harvest time, has plunged them into a severe crisis.

The District Collector has instructed the Pollution Control Board to investigate and submit a report on the incident. Additionally, the Sub-Collector, along with a committee comprising officials from various departments, is tasked with conducting a detailed investigation. The Deputy Director of Fisheries has also been directed to estimate the losses incurred due to the mass kill.

Discolouration of the water was first noticed in the Eloor area on Monday evening and thereafter spread to Cheranallur, Kadamakudy, and Varapuzha. Residents reported a pungent smell making it difficult to breathe.

Although farmers tried to save the struggling fish, all attempts were in vain. Locals and representatives halted the sale of the affected fish, sending samples to the Food Safety Department and Pollution Control Board for testing. Enraged farmers protested outside the Pollution Control Board and Varapuzha Panchayat offices with the dead fish.

Reports indicate that the unregulated discharge of effluents from industries near Periyar has caused the massive fish kill. Locals also suspect that the release of sewage, exacerbated by heavy rain, has contributed to the deaths.

"As sulphur dioxide, nitrogen dioxide, and carbon dioxide levels increase in the water, sudden pH variations can affect the fish. A decrease in alkalinity leads to pH depreciation, reducing oxygen availability and causing fish deaths," explained Dinesh Kaippilly, head of the aquaculture department at the Kerala University of Fisheries and Ocean Studies (KUFOS).

Additionally, sudden rains can drop water temperatures by up to 3 degrees, altering pH values and affecting fish habitats. Gradual changes in temperature and pH would not have such a detrimental effect.

KUFOS will appoint a team to conduct a study on the massive fish kill incident.