- Regional climate model studies in the Ganges river basin predict an increase in the mean annual temperature by 1 to 4 degrees Celsius between 2010 and 2050.
- This steep incline could potentially open up newer parts of the Ganges river to non-native species such as the common carp, tilapia and African catfish, allowing them to occupy waters previously uninhabited by them.
- These freshwater species are cultured in water bodies globally, despite being documented as invasive, with farmers and stakeholders prioritising short-term profits over impacts on the ecosystem.
New findings from regional climate model studies conducted in a 25-kilometre grid in the Ganges river basin predict a mean annual temperature rise in the waters of 1-4 degrees Celsius between 2010 and 2050. Warmer waters could allow non-native species to move into areas they haven’t been observed in before. Among the most abundantly captured invasive species that may benefit from rising temperatures are the common carp or Eurasian carp (Cyprinus carpio), Nile tilapia (Oreochromis niloticus) and African catfish (Clarias gariepinus), according to new research.
Freshwater fish are an important component of invasive alien fauna, possessing attributes that boost their ability to spread in new habitats and harsh conditions. “Most invasive species are able to adapt to changing climatic conditions since they are plastic in nature,” says A.K. Singh, Emeritus Scientist at the ICAR-National Bureau of Fish Genetic Resources, Lucknow, referring to the morphological plasticity of invasive species to respond to new environments by changing their anatomical traits. Singh co-authored the study, published in January 2022.
Native fish continue to dwindle
India’s National Biodiversity Authority (NBA) lists the Nile tilapia, African catfish and common carp as a great threat to the country’s freshwater biodiversity. These species are present in abundance, and farmed along the Ganges, given their high commercial value. However, according to the NBA, the introduction of these fish has critically depleted many native species, especially Indian carps, in major riverine systems, including the Ganges.
The impacts of climate change – primarily rising temperatures – will only enable non-natives to thrive and spread.
Though dramatic changes in precipitation and temperature patterns place added stress on both native and invasive aquatic species in freshwater systems, invasive species are far better equipped to handle new conditions. This is the edge that helps common carp, tilapia and African catfish survive in Uttar Pradesh: several areas in Kanpur, Mehndi ghat in Kannauj, Shuklaganj in Unnao, Daraganj in Prayagraj, Adalhat in Mirzapur, Saraimohana in Varanasi, Dadri ghat in Ghazipur and Ganga ghat in Ballia district.
Climate change currently affects at least 10,967 species on the IUCN Red List of Threatened Species, increasing the likelihood of their extinction.
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Despite being widely documented as invasive, these species continue to be cultured world-over. For example, a study published by the Food and Agriculture Organization of the United Nations (FAO) in 2021 observed that global tilapia aquaculture production grew exponentially from 1990 to 2018, from 380,000 tonnes to six million tonnes, making it the fourth-largest species group in global aquaculture. “Farming tilapia and African catfish improves profitability for farmers and food security for the global population. The tilapia is hardy and adaptable, and has the potential to produce multiple offspring, making it ideal for farming,” says Viplove Katiyar, who works at a farm near Amethi in Uttar Pradesh.
However, invasive fish are particularly prone to escaping from their pens and ponds. They also easily take hold in newer areas and can out-compete many local fish. “We initiated several awareness campaigns, but realised that stakeholders and farmers favour immediate gains over any consequential impacts which are realised only much later, and may be tangible or intangible,” says Singh.
According to the NBA, invasive species management is a herculean task. So far, the populations of only a species have been successfully controlled. In case of aquatic invasion management, prevention is the only cost-effective solution till date. “If any potential invader has established and colonised (a water body), there is no single method to contain and manage them. And even if such a method exists, it is highly expensive. World over, millions of dollars have been spent to eliminate invasive aquatic species, but nothing has happened,” says Singh.
“In the long term, they would have an adverse effect on the local ecosystem since they have the potential to interfere with ecological niches, biodiversity and can build their own environment to thrive in, thus disrupting ecosystem services,” says Singh.
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Banner image: African catfish in Bengaluru. African catfish find it easier to thrive in new and harsh environments. Photo by Yercaud Elango/Wikimedia Commons.