Invasive Freshwater Fish are Thriving in the Ganges, Aided by Increasing Temperatures

Environmental News from India: 

  • 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.

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Source: Mongabay

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