Threat of ‘foreign invasion’ on rivers

Exotic fish species from South America and Africa — red piranha, pacu and catfish, to name a few — are posing serious threat to the State’s fish biodiversity. Piranhas were netted by fishermen from Kanakkankadavu, Muzhikulam, Annamanada and Pothassery areas of the Chalakudi river last fortnight. “We get 5 to 10 piranhas every day from the river,” said K.M. Devassia, a wholesale fish trader in the region. Each fish weighs up to 150 gram. Anglers had hooked the fish from the Kandakadavu region too, said Mr. Devassia. Piranha, a native of South American rivers, is suspected to be clandestinely introduced to the country. The species is also available in most aquariums across the city. “Piranha feeds on anything that comes its way. It tears its food at lightning speed with its conical, canine and razor sharp teeth,” said B. Madhusoodana Kurup, director, School of Industrial Fisheries of the Cochin University of Science and Technology. If established in the natural waters, it would destroy endemic population and cause gene contamination by crossbreeding, he said. CUSAT proposes to study whether piranhas have matured and spawned in Kerala waters, Dr. Kurup added. “With its powerful dentition, piranha can inflict serious bites. It has a highly evolved hearing capacity too,” according to scientific literature. Horrifying stories of piranha attack have set the box office ringing in Hollywood. The movies have also triggered lurid fascination for the species worldwide. African catfish, another invasive carnivorous variety, was recently caught from Anavalchal, the canal that connects Periyar Lake with Kumili town, Idukki. Large number of fish swarmed the paddy fields of the area during the beginning of the monsoon. Catfish has established itself in the water bodies of the State, said V.S. Basheer, senior scientist of the National Bureau of Fish Genetic Resources, Kochi centre.“Piranhas caught from the Chalakudi river might have escaped from some farms. We need to get regular catch of the fish, with adults and fishlings, to prove that they have bred here,” Mr. Basheer said. The bureau plans to include piranhas in its monitoring programme on impacts of exotic fishes in India. Black Pacu, another native of South America, is also available in the aquariums. However, scientists certify that it is a harmless variety. Panjasium, popularly known as Malasian Vala, is another variety that was illegally introduced to the State. It is now widely farmed here. “Wholesalers supply pacu and piranha to the city aquariums from neighbouring States” said Bejoy, an ornamental fish vendor.
The Hindu, 10th August 2009