THIRUVANANTHAPURAM: Department of Aquatic Biology and Fisheries, University of Kerala, is about to start a national-level study on sucker fish invasion in various states. From across the country, there have been reports of invasion by Suckermouth armoured catfish, which is bought by hobbyists, fish breeders and aquarium owners as an ornamental pet.
The latest report was about its invasion in the drainage of Thiruvananthapuram, revealed by a study conducted by the Department along with Rajiv Gandhi Centre for Biotechnology (RGCB) here. The fish has managed to establish its population in the freshwater canals of Thiruvananthapuram, nearly wiping out the previously abundant pearl spot (‘karimeen’) and freshwater barb (‘para’), according to the report.
The study was conducted by A Bijukumar, Head of Aquatic Biology and Fisheries Department, with R Smrithy Raj, a research scholar at the Department; Sanil George, scientist, RGCB; and U Sureshkumar, DNA Examiner, RGCB. They have been observing the population of the fish over the past two years in the drainage of capital city - especially Amayinzhanjan Thodu.
A survey conducted by Bijukumar revealed that a huge number of hobbyists and aquarium owners were unknowingly aiding the invasion. The fish, which would be a “cute 5-10 cm pet” when young, would outgrow the aquarium in a year’s time. Not wanting to skin the fish and unaware of its invasive nature, the owners would let the fish out into drainage, says Bijukumar.
The study began when local fishermen shared that the so-called ornamental fish, displayed at Aquarium Shows, were easily available in the canals. A net dropped into a canal would fetch 50 kilograms of fish.
Sucker fish is three times faster in invading the waters than Tilapia, another invasive fish found in Kerala. The latter had taken about thirty years to pervade, while the former took less than a decade. One of the reasons for this is that sucker fish has no natural predators in India. Cormorants and other birds which feed on fish avoid it, because of its hard armour and spiny fins. In South America, its native country, it is eaten by pelicans and crocodiles.
Another reason why it has been able to thrive in Thiruvananthapuram’s drainage is that the quality of water has dropped over the last ten years. Unlike a pearl spot which is sensitive to changes in water quality, the sucker fish can survive on organic waste and poor oxygen levels in the water. Moreover, it eats eggs of other fish species, and uproots aquatic vegetation.
The world over there have been reports of invasion by sucker fish. The study by the Department and RGCB suggests that the fish be used as food, but not before studying whether it is contaminated in any way.
Though the researchers were able to identify the genus of the fish as ‘Pterygoplichthys’, they have not been able to put a finger on the species. The researchers believe that this could indicate the presence of hybrid species, which have adapted to adverse conditions even better than their parents.
The report of the fish’s invasion in Thiruvananthapuram will be submitted to the Ministry of Environment and Forests as well as Kerala State Biodiversity Board.
The researchers hope that this will help form that much needed legislation which prevents the release of potentially damaging species like these into natural water bodies.
They also hope that it will prompt the authorities to conduct awareness programmes amongst hobbyists regarding invasive alien species.
A national-level study will help this further, they believe.