The local aquatic ecosystem is increasingly facing threat due to the uncharted growth of invasive fish species, especially African sharp tooth catfish. The situation is further precipitated due to general ignorance about the menace posed by the fish species and its resemblance to Goa’s tigur species. Clarias gariepinus, as it is known by its scientific name, is an air breathing exotic catfish that also belongs to Clariidae family of Goan catfish (tigur). During the monsoon season, it appears in fish catches from rivers, creeks, channels, khazan lands and even from rice fields. A study by fisheries scientists of Indian council of agricultural research-central coastal agricultural research institute (ICAR-CCARI), Old Goa raises a concern about this exotic species posing a threat to the local fish biodiversity and sustainability of the aquatic ecosystems. The hardy fish can breed easily in tough conditions, as it feeds on all types of food. It also appears to be a voracious predator. “It is a major menace as it disturbs the natural trophic status of the ecosystem and deprives other native species of their food and breeding space and it also feeds on these fishes,” scientist, fisheries science, ICAR-CCARI, Manju Leskhmi N said. The numbers of the invasive fish species grow fast and it proliferates easily in all ecosystems due to its high fecundity and survival rate. “One individual can release 4 lakh eggs in a single season,” scientist, fisheries science, ICAR-CCARI, Sreekanth GB said. In comparison, the local tigur species (Clarias batrachus) has a lower fecundity, in the range of 7,000 to 15,000. Goan catfish population may have depleted in recent years due to the presence of the exotic species as also other reasons, but there has been no study to asses these aspects. “African catfish preys on local aquatic species and may greatly deplete in future all native species from the ecosystem,” director, ICAR-CCARI, N P Singh said. African catfish can grow up to 1.7m and normally matures at 90cm. Breeding in swampy, shallow water bodies with soft muddy substratum, its maximum reported age is 15 years. “Once these species enter the natural ecosystem, it may be very difficult to control their proliferation because they are more resilient and reproduce faster than native species,” Sreekanth said. Catches have also been reported from Carambolim lake during the last three years. “During the last week of June, we caught six individuals for our studies from small water channels in the ICAR complex linked to the Carambolim lake,” Lekshmi said. The invasive species is suspected to have spread in Goan waters after being introduced clandestinely in ponds by aquaculturists for commercial production. “Other persons and fishermen may be propagating this species in their wells and ponds due to its resemblance to tigur, least knowing that it poses a threat to local species,” Lekshmi said. Conservation biologist, Aaron Lobo, agreed, “The problem with African catfish is that many people mistake it for tigur. The people need to be educated about its impact on the environment and the health of local ecosystems.” Department of animal husbandry, dairying and fisheries (DAHD) had banned the rearing of African catfish in 2000 under the Environmental Protection Act, 1986 due to its adverse impact on local fish species and ecology. Director of fisheries Shamila Monteiro said that the invasive fish species impacts local fish population. “We need to create awareness among people that it is a banned species,” she said.
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