Alien invaders displacing local fish in the Yamuna River

A team of scientists studying the fish population in the Yamuna River, the largest tributary of the Ganges in northern India, have found that alien fish species are now dominating the 950km stretch of river.

Data was gathered from 15 sites between May 2011 and March 2013. From a total of 63 fish species recorded, ten were identified as alien invasive species. There was a predominance of the alien fish species at most of the sampling locations. The invasive species included carp, Clarias catfish and Nile tilapia.

India’s National Bureau of Fish Genetic Resources stated in its report: "The main reasons attributable to the decline in fishes are habitat destruction and fragmentation, water abstraction, industries and increased incidences of alien invasive species in particular".

The "deliberate or accidental introduction" of the alien species was identified as a key component of the human-induced biodiversity crisis that is harming native species and disturbing the ecosystem processes.