Several popular aquarium fish species that have found their way into Kerala’s natural water bodies could pose serious threats to the aquatic biodiversity here, according to a recent study.

The study, published in the latest issue of 77-year-old science journal Current Science, brought out by the Current Science Association and the Indian Academy of Sciences, points out that several ornamental fish which were released into natural water bodies either because their owners grew tired of them or because they became too large or prolific for their aquaria, could pose serious consequences for the rest of the aquatic fauna.

K. Krishnakumar, one of the authors of the study, says at least 11 species of exotic aquarium fish have been found in inland waters of the State. Of these, four are popular aquarium pets – the Guppy (Poecilia reticulata), Three-spot Gourami (Trichogaster trichopterus), Platy (Xiphophorus Maculatus) and Sucker Catfish (Pterygoplichthys multiradiatus).

Guppies were collected from second-order streams of Chalakudy River and were found to be present in good number in branches of Meenachil River in Kottayam apart from in “drainage canals of Ernakulam city”,

which are connected to various natural water bodies like the Vembanad Lake.

“Since they require a very short time to mature, guppies have every chance of proliferating and becoming a potential pest in our inland waters,” says Mr. Krishnakumar.

The three-spot gourami, on the other hand is a new entrant. It was only recently that 21 individuals of this species were found from canals that empty into the Vembanad Lake, the first report of the species from natural waters of Kerala. The gourami, the study notes, is an “opportunistic carnivore having territorial and aggressive behaviour that can prove harmful to native species.”

The Sucker Catfish, found in Vylathur of Thrissur and the Chackai Canal of Thiruvananthapuram, can alter and reduce food and physical cover for other aquatic insects because of its algae-devouring habits.

“Such aquarium species introduced purposefully or accidentally into natural water bodies can adversely affect local fauna through genetic pollution, disease introduction and ecological impacts, such as

predation, competition and environmental modification. Effective quarantine measures are required as a precaution,” the study notes.

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