Source traced to commercial and ornamental fish farms

The catastrophic floods that caused widespread havoc throughout the State last month have also released several alien species of fish into waterbodies, raising a threat to the endemic aquatic ecosystem and biodiversity, scientists have reported.

A joint research team which carried out a rapid assessment of the impact of the floods on waterbodies has documented the presence of 11 alien species, including the alligator gar (Atractosteus spatula), arapaima (Arapaima gigas), arowana, giant gourami, grass carp, kissing gourami, (Helestoma temminckii), koi carp, gold fish (Carassius auratus), shark catfish also known as Malaysian vaala, red-bellied pacu (Piaractus brachypomus) and three-spot gourami and four alien invasive species namely the East African catfish, common carp, tilapia (both cultivated and ornamental varieties) and sucker catfish.

The researchers from the University of Kerala, Kerala University of Fisheries and Ocean Sciences (KUFOS) and the National Institute of Advanced Studies (NIAS), Bengaluru, have established that the alien species had escaped in large numbers from flooded commercial and ornamental fish farms.

Major route

“Globally floodwaters have proved to be a major route for the spread of invasive species and, therefore, a precautionary approach is warranted while farming potential invasives along floodplains,” says A. Biju Kumar, Professor, Department of Aquatic Biology and Fisheries, University of Kerala.

According to Rajeev Raghavan of KUFOS and the South Asia Coordinator of the IUCN’s Freshwater Fish Specialist Group, the proliferation of alien species poses a serious threat to the freshwater ecosystems of Kerala, considered a global hotspot for fish diversity, with about 200 freshwater species of fish, about 30 percentage of them endemic. The scientists have called for a ban on the import and farming of alien species like the arapaima and alligator gar.

Endemic to the Amazon, the Arapaima grows up to 4.5 metres in length and 200 kg in body weight, while the alligator gar, native to the US and Mexico, reaches a body length up to 3 m and and weighs around 137 kg. Both the species feed voraciously on fish and hence have the potential to cause serious threat to the indigenous fish in the rivers of Kerala.

Another escapee, the red-bellied pacu which was extensively cultivated in several districts, is currently caught in large numbers from the Vembanad and kole wetlands and backwaters of Kuttanad. A native of South America, it is omnivorous, devouring everything from fruits, seeds and nuts to insects, small fish, crustaceans and zooplankton.

The research team found that the species now abounding in Kerala waters had developed a preference for snails.