African catfish posing threat to native fish species

 The species 'Clarias Garipeneus' - known in local parlance as African mushi, introduced a few years back as part of acquaculture, has proliferated in dangerous proportions in all rivers and brooks in hilly Wayanad district, which is part of the Neelgiri biosphere.

When a group of tribals recently went fishing in the Noolpuzha river, a tributary of the Kabani, all they netted was some heavy catfish, whose unsavoury flesh has very little demand in the market.

Besides multiplying fast, this predator fish has an ability to multiply even in adverse ecological situations compared to other native varieties, which have a tough time due to environmental degradation, according to Babu Mylambadi, secretary of environmental group Wayanad Prakrithi Samrakshana Samiti (Wayanad environmental protection committee).

Other main rivers in the district like Karapuzha, Narasipuzha, Thalipuzha, Mananthavadi, Panamaram and all tributaries of Kabani have been facing the same threat.

This catfish breeds so fast that they virtually dominate the rivers here. "It is difficult for other types of fish to survive among these carnivorous killers, " a tribal fisherman from Muthanga said. 

Fresh water fishing traditionally provides a supplementary income to hard pressed tribals in the district, especially during monsoon when demand for other manual jobs come down sharply.

The biosphere has over 50 indigenous species of endemic inland water fish, as found in a survey conducted in the Kabani river, according to Prof. Madhusoodhana Kurup of the Cochin University of Science and Technology.

The unique inland water fish varieties identified by the survey included Giant Mahseer (Torputitors), which has mostly been seen in the Himalayan water bodies, Thonnivala (Silerrus Wayanadencis), Kallemutty (Kantaka Vidorsalis), Poovan (Schistura Striatus) and Poocha Mathsyam (Glyptothorax Anamalaylensis).

According to Prof. Kurup, the increasing population of the catfish may even wipe out indigenous fish varieties.

The rapid spread of the killer fish may adversely affect the 'Mathsya Keralam' project, seeking to promote inland fishing in the district, Babu said.

African catfish was introduced in the area for captive breeding in ponds of the aquaculturists. During flooding in monsoon season, many of them found their way into nearby paddy fields and from there, to the rivers through streams and canals, he said.

According to environmental groups, some of the countries which faced this problem have banned supply of catfish juveniles for agriculturists.