KATHMANDU — The invention in a Nepali river of an armored catfish native to the Amazon has alarmed researchers and conservationists, who say it’s nonetheless not clear how the species discovered its manner from the South American rainforest to the Himalayan nation.
Forty-three specimens of Pterygoplichthys disjunctivus, generally known as the vermiculated sailfin catfish, have been found within the Lohandra River throughout surveys of assorted rivers in japanese Nepal from Might 2019 to July 2023. The findings have been documented in a newly printed examine within the journal BioInvasions Information.
“Our examine for the primary time reveals the presence of genus Pterygoplichthys fish in Nepal’s river system,” examine co-author Asmit Subba, a zoologist at Tribhuvan College in Kathmandu, advised Mongabay. “Nonetheless, we will’t conclusively say the place the fish got here from.”
Fish within the genus Pterygoplichthys are generally known as “janitor fish,” as they’re utilized in aquariums to eat algae and maintain the tanks clear. From the Amazon Basin by way of the aquarium fish commerce, they’ve since discovered their manner into river methods around the globe, together with in South Asia, East Asia and the U.S.
P. disjunctivus is customized to dwelling within the murky waters of the Amazon, the place it swallows air and absorbs the oxygen by means of its intestinal linings reasonably than extracting oxygen from water the way in which most different fishes do. This capacity permits it to outlive even when it’s out of water for hours. “Due to its vermiculated scales, it’s very troublesome to kill and never even palatable to people,” Subba mentioned.
Hari Sharma, an affiliate professor of zoology at Tribhuvan College, who wasn’t concerned within the examine, mentioned the species had beforehand been recorded “in numerous ponds in southern Nepal,” however that what the brand new paper paperwork are in all probability the primary findings in a river within the nation. He mentioned the invention must be taken significantly because the fish might have a huge effect on freshwater ecosystems throughout Nepal.
In neighboring India, numerous Pterygoplichthys species have been recorded in Bihar, Uttar Pradesh and West Bengal — three states that border Nepal — in addition to farther south in Andhra Pradesh, Telangana, Maharashtra, Kerala and Tamil Nadu states. In areas the place they’ve unfold, fishers have reported declining catches of native fish, elevating the alarm that the invasive species are displacing and even killing off native species.
For his or her examine in japanese Nepal, Subba and colleagues used numerous fishing instruments to scour a community of eight rivers, together with the Lohandra, which flows south into India. After they encountered fish they suspected weren’t native, they photographed them of their pure habitat to doc their look precisely. They then preserved the captured fish in an answer for later evaluation.
When it got here to P. disjunctivus, they confirmed the specimens’ identification by means of shut examination of their bodily traits, corresponding to measurement and form, and evaluating them to identified species.
The findings have raised a number of questions that stay unanswered for now, chief of which is: The place did the janitor fish come from?
One attainable reply is that they swam upstream from India. Nonetheless, Sharma mentioned he’s not satisfied that was the case. “If it had come from India, why was it that the people have been present in a sure stretch of the river” reasonably than extra extensively, he mentioned.
He added that as a result of janitor fish can survive in harsh situations, they’re a sought-after species for releasing into rivers as a part of spiritual rituals. “Native fish can’t survive in plastic luggage or containers. Merchants wouldn’t need the fish to die earlier than they’re launched into the river,” Sharma mentioned. This, he added, suggests the specimens found might have been regionally launched into the river.
However that speculation has a key flaw: A lot of the pet commerce in fish in Nepal is concentrated in large cities corresponding to Kathmandu and Pokhara, and never a lot within the space the place the janitor fish have been discovered, Subba mentioned.
One other query raised is whether or not the species has unfold to different rivers within the nation. There’s no definitive reply, Subba mentioned: “Though we didn’t discover the fish in some other rivers we surveyed, we will’t say for sure that they aren’t there.” Provided that the river community within the area is interconnected, there’s a very good likelihood this species has moved upstream from India and into different river methods in western and central Nepal, he added.
No matter how the fish discovered their manner right into a Nepali river, their presence right here might have extreme impacts on freshwater ecology throughout the nation, including to the litany of different stresses being placed on Nepal’s rivers, researchers say. Real Prajapati, an aquatic biologist at Tribhuvan College, who wasn’t concerned within the examine, mentioned the shortage of predators for P. disjunctivus within the Himalayan river system is the main concern. “As we don’t have predators who can kill these vermiculated fish, they may proliferate in a short time and displace native species of fishes,” she mentioned.
There’s already precedent for this. A 2020 report commissioned by USAID recorded 16 species of unique fish in Nepal, starting from the Nile tilapia (Oreochromis niloticus) to the rainbow trout (Oncorhynchus mykiss), each of that are farmed for meals. “Equally, we’re additionally seeing a large invasion of glass fish corresponding to Chanda nama,” Prajapati mentioned.
The report states that Nepal lacks procedures and requirements for aquarium merchants and farms to launch waste and effluent into pure water our bodies, and this could possibly be the main supply for invasive species proliferating in rivers. Equally, legal guidelines are wanted to control the import of aquatic species into the nation, it provides.
Local weather change, a cross-cutting challenge, is also enjoying a task within the proliferation of invasive species. “As Nepal is a geographically various nation, we might see species from the lowlands transfer upward to the hills and mountains and vice versa,” Prajapati mentioned, including that invasive fish aren’t essentially simply those who come from exterior the nation.
Whereas some measures will be adopted over the long run to handle the problem of invasive species, others should be taken instantly, researchers say. Within the case of the janitor fish, the federal government wants to extend consciousness, particularly amongst fisherfolk, Subba mentioned. “The one manner we will management its unfold is by killing it each time and wherever we discover it earlier than it will get too late,” he mentioned.
Quotation:
Limbu, J., Rajbanshi, D., Subba, A., Khanal, L., Yang, J. Q., & Li, C. (2024). First report of the non-native vermiculated sailfin catfish Pterygoplichthys disjunctivus (Weber, 1991) from Lohandra River, Japanese Nepal. BioInvasions Information, 13(2), 557-564. doi:10.3391/bir.2024.13.2.20
This article by Abhaya Raj Joshi was first printed by Mongabay.com on 20 June 2024. Abhaya Raj Joshi is a workers author for Nepal at Mongabay. Discover him on @arj272. Lead Picture: A large otter with an Amazonian catfish catch. Picture by Bernard Dupont by way of Flickr (CC BY-SA 2.0).
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