Chennai: The invasion of a South American endemic fish, which is known to act as tank cleaner, is threatening the existence of ingenious fish varieties in fresh waters in Tamil Nadu. The State Planning Commission’s Land Use Research Board has sponsored a study in Vaigai and Cauvery river basins to assess the impact of the fish on the local fresh water ecosystem.
The non-edible and devilish fish, Pterygoplichthys pardalis, was seen along the banks of the Vaigai river from Madurai to the Gulf of Mannar occupying the local ecosystems of Madurai and Ramanathapuram districts. “The recreational practice of collecting exotic species and their subsequent escape or release pose a significant threat if accidentally released or dumped to the local fresh water system,” said S.Chandrasekaran, invasion ecologist and associate professor, department of plant science, Madurai Kamaraj University.
The team, headed by S.Chandrasekaran, is to undertake the study in Madurai, Ramanathapuram, Tiruchi and Thanjavur districts where it will examine how far the invasion has occurred in the river basins and its impact on the indigenous fish population. “This particular fish is restricting the growth of the indigenous fish varieties. We intend to study how it is impacting the growth of local fish population,” Chandrasekaran said.
Scientists have in the past cautioned that African and South American catfish, guppies and suckermouth catfish are among exotic species that have moved into local water bodies and are competing with indigenous fish. “The fish introduced as a pet has now become a pest. This non-edible and unmarketable fish outranked all other edible fishes both in abundance and biomass production. It could harm our freshwater bioresources,” he said.
The research team has conducted a detailed case study after noticing a recurring occurrence of tanker fish in the catches from the Vandiyur Lake in Madurai. “Its abundance and biomass in the fish catches from the lake varied daily and widely. However, it occurred consistently in all day catches and quantitatively exceeded all other edible fishes both in abundance and biomass,” they observed.
“It does not hold any known secondary values and its unmarketable biomass after harvest is being discarded on the shoreline. It is not even scavenged by birds or carnivores,” he said. “Local people depend on the freshwater fishes for the protein. This invasion of the tank cleaner fish can affect the protein source of the poor people. Some are alleging that these fishes are being transported to the poultry farms,” he added.
