Kozhikode: Four members of a gang accused of poisoning a tributary of the Chaliyar River to catch fish were arrested by the Feroke police, exposing an illegal practice that residents say has continued for years.

The arrested have been identified as Murshid (31) of Muthuvallur in Malappuram, K P Muhammed Anees (33) of Ugrapuram near Areekode, K Hamsa (39) of Cheruvayur in Edavannappara, and Abdul Jaleel (47) of Cheekode near Edavannappara.

According to the police,  the accused poured a highly toxic substance into a stream near Chethupalam, a tributary of the Chaliyar River. The poison would drift several kilometres downstream, causing fish to become unconscious and float to the surface. The gang then placed fishing nets near the Muttiyara canal and scooped up large quantities of fish, said police.

The practice is believed to have caused the death of thousands of fish every year in the Pullippuzha stretch of the river, triggering widespread concern among local communities.

Residents said they had been trying for years to catch the culprits. The breakthrough came in the early hours of Tuesday when local residents, who had organised a coordinated watch, spotted the gang near the Muttiyara canal. On seeing the villagers, the accused jumped into the river and swam towards Chelambra to escape.

The gang left behind the autorickshaw in which they had arrived at the spot. Local residents immediately launched a search and alerted the police. Meanwhile, another accomplice arrived in a separate autorickshaw, allegedly to help the three men who had escaped through the river. He was intercepted by residents near the Chelambra Silk Bridge and handed over to the police. During questioning, police obtained information about the whereabouts of the three men who had fled by swimming, leading to their arrest.

Police have launched further investigation into the case, including the source of the toxic substance used in the illegal fishing operation.