Amazon catfish invasion threatens aquatic biodiversity

News Desk 

Islamabad: The discovery of an invasive fish species in the waters of Sindh and Lower Punjab has raised serious concerns among conservationists, with WWF-Pakistan warning that the spread poses a growing threat to aquatic biodiversity and the country’s fisheries-based livelihoods.

According to WWF-Pakistan, an unusual fish brought to Karachi Fish Harbour on January 4 from a dhand near Sukkur could not initially be identified by fishermen or traders. The species was later confirmed as the Amazon sailfin catfish, an exotic fish native to Latin America that has now established itself in Pakistan’s natural water bodies.

The Amazon sailfin catfish is widely traded as an aquarium fish worldwide but is known to be a highly successful invader when released into open waters. Characterised by a thick, armoured body covered with bony plates, the species thrives rapidly once introduced. 

WWF-Pakistan said the fish has already spread across Sindh and Lower Punjab, making eradication or effective control nearly impossible.

The organisation said the species is among at least 26 invasive fish species introduced into Pakistan either deliberately or accidentally. These species have disrupted aquatic ecosystems by outcompeting native fish for food and space, preying on indigenous species, spreading diseases and altering habitats. 

Such invasions, WWF-Pakistan warned, can lead to biodiversity loss, ecosystem degradation and significant economic damage to fisheries.

“Invasive species can increase water turbidity, cause native fish extinctions and result in major losses in commercial fishing revenue,” the organisation said, adding that rivers, streams and lakes across Pakistan are particularly vulnerable to such ecological disturbances.

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WWF-Pakistan placed the latest discovery in a broader historical context, noting that Pakistan has a long record of introducing exotic fish species in the name of enhancing fish production and aquaculture.

Brown trout and rainbow trout were first introduced in Khyber Pakhtunkhwa in 1928, followed by several species in the 1960s, including Mozambique tilapia, common carp, goldfish and grass carp, primarily to boost production and control aquatic weeds.

However, many of these species became invasive, severely affecting indigenous fish populations. Further introductions in the 1980s, including silver carp, bighead carp and Nile tilapia, also established themselves in natural ecosystems, often at the expense of local fauna and flora. Environmental considerations, WWF-Pakistan noted, were largely ignored at the time.

The introduction of tilapia in particular had devastating consequences for major freshwater bodies. 

Fish production in Manchar and Keenjhar lakes declined sharply due to the prolific breeding of tilapia, resulting in partial or complete eradication of commercially valuable native fish species and causing serious socio-economic hardship for local fishing communities.

In recent decades, several catfish species, including North African catfish, walking catfish, magur catfish and channel catfish, have also spread rapidly in Pakistan’s waters, further threatening native fish diversity.

Beyond deliberate introductions, WWF-Pakistan highlighted the growing role of the aquarium trade in the spread of invasive species. Fish such as the Amazon sailfin catfish, guppies and mollies are often released into natural water bodies due to poor regulation and improper handling, particularly in urban and peri-urban areas.

“These species are creating havoc in natural water bodies across the country,” WWF-Pakistan said, stressing the urgent need for stronger regulation, public awareness and coordinated action to prevent further ecological damage.