Tirur: Local snakehead fish have been replaced by the Bengal snakehead while the catfish, once common in local water bodies, have completely disappeared. A survey conducted by students in the backwaters and paddy fields of Thirunavaya, as part of their academic studies, has revealed that several freshwater fish species are facing extinction.

The snakehead fish species, locally known as Kannan, has vanished from many areas and has been replaced by the Bengal variety. The students’ survey revealed that many freshwater species such as eel, pooyan (whitefish), red snapper, karuthala, leaf fish, beltfish and codfish are now rare in several regions.

On the other hand, species like cheran, anabus, valarthu vaala (ribbun fish), cutla (katol), kuyilu (Deccan Mahseer) and red-bellied pacu have proliferated in the water bodies. Many of these were introduced by agencies including the Fisheries Department. Some species were washed in from other regions during the last flood and have since multiplied.

It is believed that fishing during the breeding season, excessive use of chemical fertilisers, otter attacks, pollution, and the spread of non-native fish species have all contributed to the decline of local fish populations. The disappearance of water bodies and paddy fields is also considered a contributing factor, according to the students.

The students have called for the replacement of fingerlings of foreign fish species with native varieties. The survey was conducted by students of Thirunavaya AMLP School. The students carried out the survey in two rivers and the backwaters, referring to a book on fish published by the State Biodiversity Board.