Decline in the population of indian native fishes due to introduction of Clarias gariepinus in river Yamuna can be categoriesd as

Solution & Explanation

Answer: (4) Alien species invasion. [option D] Solution: Clarias gariepinus (the African catfish) is an introduced alien species, and the decline of native fishes following its introduction is a classic case of alien species invasion, one of the Evil Quartet causes. It is not co-extinction (1, which needs an obligate associated species), not habitat fragmentation (2), and not over-exploitation (3, which refers to human harvesting). NCERT: NCERT Class XII Biology, Ch 13 Biodiversity and Conservation, p.223, lines 18-20: "The recent illegal introduction of the African catfish Clarias gariepinus for aquaculture purposes is posing a threat to the indigenous catfishes in our rivers." (under heading Alien species invasions, p.223, line 9).