By Navaraj Kattel,Biratnagar, June 13: A non-native fish species has been found in Belbari and Dhanpalthan of Morang district. This fish, originally from the Amazon River in South America, has spread to East and South Asian countries in recent years.
The fish, scientifically named Pterygoplichthys disjunctivus, was first spotted in Nepal in Belbari, Morang, four years ago. Suspecting it to be a new species, local researchers Jashang Limbu, Deepak Rajbanshi, Asmit Subba and Laxman Khanal began investigating it at that time.
With the assistance of two Chinese researchers, Jin Quan Yang and Chenhong Li, it was confirmed that this highly invasive fish was a new species for Nepal. The researchers wrote an article about their findings, detailing the habitat, physical and genetic makeup, and behaviours of the fish. The article was recently published in the scientific journal BioInvasions Records.
According to the article published in the esteemed (Q2) scientific journal, 43 samples of the fish were collected from the Lohandra River. Studies were conducted at 50 locations along the major permanent rivers of Eastern Nepal, including the Tamor River. This species, along with another of the same genus, was found in two locations on the Lohandra River and in the rivers near Damak, Jhapa.
Visually attracted samples, weighing between 200 and 300 grams, were collected. One of the researchers, Jashang Limbu, said that they suspected the fish either escaped from someone’s aquarium into the natural river system or arrived via rivers from India.
Regardless of how it arrived, the fish has been found to outcompete native species in Nepal, eating their food and preying on their eggs and young. This poses a threat to local fish populations, potentially leading to their extinction. This invasive species has caused similar ecological disruptions in many countries, destabilising natural ecosystems.
Limbu said, “At first, this fish appears shy and remains still, but it becomes aggressive towards native fish, biting and preying on their young. It has been proved in the Lohandra River in Morang.”
Researchers discovered in 2019 that this fish was already established in the Lohandra River, and its population is continuously increasing. There is also a risk of it spreading to other rivers and fish ponds.
“If it enters commercial fish ponds, it can cause significant damage. This American fish is usually kept in aquariums for its beauty, but it is not the species to eat,” said Limbu, adding that people do not prefer to eat it because it does not taste good.
Researchers have suggested immediate control measures for this invasive non-native species. In their article, they stressed the need for policy-level intervention to further research and control this fish.
If left unchecked, it could jeopardise the livelihoods of those who depend on fishing, cause significant economic losses, and challenge the natural ecosystem.
According to statistics, Nepal hosts 260 fish species, including Pterygoplichthys disjunctivus. Of them, 18 species are non-native and 17 are endemic to Nepal.
