Kerala - Kochi   

Exotic fish posing threat to native species: study

Special Correspondent

"The presence of a well-established population of tilapia in the Chalakkudy river will invariably cause negative effects on the native fish fauna."

KOCHI: A study on the fish in the Chalakkudy river has shown that at least four exotic species found in the river are `potential pests' capable of driving into extinction many of the native ornamental fish species.

The study found five exotic species — tilapia, mosquito fish, giant gouramy, platy and guppy — thriving in the river. Four of these pose threat to the natives in the river which is known for its rich fish diversity.

"Their occurrence and possible spread through the river system could spell doom for the many endemic and threatened native ornamental fish species," the study warns. The study, conducted by Rajeev Raghavan and Benno Pereira of Department of Aquaculture, St. Albert's College, Kochi and Gopal Prasad and P.H. Anvar Ali of Kerala University's Department of Zoology, was part of the All Catfish Species Inventory Project of the National Science Foundation of the U.S.

"Our findings on the occurrence of exotic fish species in a fish diversity hotspot like the Chalakkudy is of critical concern since the river harbours many endemic and threatened fish species that have higher chances of getting endangered," the researchers say in an article that will appear in an upcoming issue of `Biological Invasions' published in the Netherlands.

They point out that the river system harbours an exceedingly rich ichthyofauna of 98 species. It had attracted scientists' attention following the discovery of many new species.

Of the four `potential pests,' tilapia is especially harmful to the native species. Because of the proliferation of tilapia, several fish species had declined in many water bodies, including reservoirs, in India.

"The presence of a well-established population of tilapia in the Chalakkudy river will invariably cause negative effects on the native fish fauna of the region," the article says. The immediate threat would be to a species called Etroplus maculates (Orange Chromide.)

The researchers have called for a detailed study of native-exotic fish interactions and related aspects to find out the impacts of the exotic fish on the native ones.

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