Industrial Effluents Claim Fish Lives in Periyar

Abraham Jefin, a 29-year-old inland fisherman from Kadamakkudy in Kochi, deftly wielded his Chinese net into the Periyar river, under the moonlit sky of May 20. He discovered a large number of fish immediately trapped in his net. Upon closer inspection, however, he realised that most of them were dead.

“I hurried to inspect the fish in my river cages. I saw pearl spot, sea bass, and red snapper showing signs of distress and thrashing violently inside the cages. Around 2 a.m. the next day, all the fish in the cages died. Also, dead fish were seen floating in the river outside the cages. Polluted water, which reached our area when the regulator opened its shutters, caused the fish kill. The river water was contaminated due to effluents from nearby factories,” said Jefin.

Subbayan T.R., a cage fish farmer in Eloor, east of Kadamakkudy, said that around 60 families in the area suffered losses due to the fish kill. “The pungent odour from the dead fish in the river made it extremely difficult to live in our area for several days following the incident. However, no proper action has been taken against those polluting the river, nor is compensation provided to fish farmers,” Subbayan told Mongabay India.

For the next few days, Jefin spent most of his time cleaning his river cages and removing the dead fish. He estimated a loss of around Rs. 10 lakhs (Rs. one million). “Usually, when the regulator shutters open, polluted water reaches our area and causes fish kills. Previously it affected only 10 or 20 percent of the fish in my cages. However, for the first time, it caused widespread destruction of fish in the river,” he added.

Dickson Vaduthala, a fisherman from Vaduthala, was also using a Chinese net to catch fish around 2 a.m. on May 21, when he noticed an unusually high catch. Initially, he was pleased with the large catch, but he soon realised that the fish kill in the river had caused the abundance. “When I arrived at the market at dawn to sell the fish, I found various types of fish already piled up. I was informed that due to increased pollution in the river, most fishermen had caught dead fish and couldn’t sell them that day. Later, I returned home and buried the fish near my house. The river might not provide a sufficient catch for me in the coming months. I will need to find alternative ways to earn money for my family,” Dickson said.

The release of polluted water

Approximately 5.5 million residents of central Kerala rely on the Periyar river for various needs, including drinking water, farm irrigation, fishing, and aquaculture. The 244-kilometre river has been celebrated in poetry for its role as a conduit for cool breezes from the Western Ghats.

The residents of the industrial areas in the district, including Edayar, Eloor, Varapuzha, Kothad, Kadamakudy, Cheranallore, and Kottuvally, were significantly affected by the fish kill.

The Kerala University of Fisheries and Ocean Studies (KUFOS) and the Central Marine Fisheries Research Institute (CMFRI) in Kochi conducted a study on fish kill incidents in the Periyar river. The findings of scientists at KUFOS and CMFRI confirm that the concerns fish farmers have about the reasons for fish kills are indeed valid.

According to a KUFOS report that Mongabay India accessed, on May’s fish kill incident in Periyar, the fish mortality was caused by the opening of three gates at the Pathalam regulator-cum-bridge: one at 3:30 pm and two more at 6 pm on May 20, resulting in the discharge of polluted water. The state irrigation department reported that the gates were opened due to rising water levels from the Bhoothathankettu barrage and heavy rainfall on that day.

“The Periyar river experienced a severe fish mortality event beginning on that evening, escalating to catastrophic levels by the following day. The incident originated downstream of the Pathalam regulator, resulting in the deaths of hundreds of thousands of fish and other aquatic life forms,” the report said. It recognised the ecological and economic repercussions of the decision, confirming that the discharged water contained “harmful substances and reduced oxygen levels, resulting in a significant number of fish dying downstream”. The report found that water upstream of the regulator had stagnated, accumulating organic matter like household waste, public drain runoff, decaying plant and animal matter and anthropogenic effluents from markets, hotels and other sources. This led to the production of harmful gases like hydrogen sulphide, methane, ammonia, and more.

The report also notes that while minor fish deaths occasionally occurred in the Periyar, the severity escalated to catastrophic levels due to increased pollution from industrial sources. “Localised fish kills linked to the opening of the Pathalam regulator shutters have been recurring for decades. Field inspections, sample collection, and laboratory analyses revealed that elevated levels of hydrogen sulphide were the primary cause of the fish kill, exacerbated by higher levels of ammonia. These factors, coupled with decreased dissolved oxygen levels, created lethal conditions for most aquatic organisms, from microbes to fish,” the report said.

“In addition to these factors contributing to the fish kill, alarming concentrations of heavy metals and toxic chemicals were detected in the water, sediment, and fish.” The report emphasised how this disaster underscored the urgent need for stringent controls on effluent treatment and discharge, enhanced monitoring of polluting industries, and real-time surveillance of surface and bottom water as well as sediment both upstream and downstream of the Pathalam regulator.

An official from CMFRI, who spoke to Mongabay India on the condition of anonymity, also attributed the sudden stress caused by polluted water from the Pathalam regulator to the fish kill. “Low dissolved oxygen levels are also a contributing factor to the fish kill. In some areas, dissolved oxygen was as low as 1 mg/L. Fish kills typically occur when dissolved oxygen levels drop below 3 mg/L. Biochemical oxygen demand (BOD), which indicates high organic pollution in the water, and chemical oxygen demand (COD), which indicates lower available oxygen for fish and other aquatic organisms, were very high,” the official said.

The official further stated that they detected toxic chemicals in the deceased fish from the river. “Our examinations of the gills, kidneys, and livers of the deceased fish revealed that toxic chemicals were responsible for their demise. Typically, during fish kills caused by low oxygen levels, only the gills are affected. However, our tests showed damage to organs such as the kidneys and liver, indicating that chemical toxins in the water caused the fish mortality,” he said.

In response to the mass fish kill in the Periyar River on May 20 and 21, the Kerala government has directed the Department of Irrigation to develop a standard operating protocol for lifting the shutters of the regulator-bridge at Pathalam. A coordination committee, comprising representatives from the Fisheries, Irrigation, and Local Self-Government departments, as well as the Pollution Control Board (PCB), has been formed for this purpose. Following the incident, fisheries minister Saji Cherian announced that a total compensation of Rs. 13.55 crores to fish workers who have incurred losses. However, the fishermen have not yet received their compensation.

This story was first published on Mongabay India

Photo sources: cover photo, Periyar river