Native fish species face threats from India's river interconnection plan: Study

A new study shows that India’s plan to connect its rivers could lead to the spread of invasive fish species. This could harm the habitats of endangered fish and pose threats to the environment, economy, and livelihoods. The plan involves creating a network of canals, reservoirs, and channels to connect major rivers and manage water issues.

The study, published in The Environmental Monitoring and Assessment, lists areas at risk, including biodiversity hotspots in the Western Ghats, northeast India, and the Sundarbans delta.

The researchers warn that the river-linking projects could threaten native freshwater species. Invasive species can harm ecosystems by competing for food and space, often negatively affecting native species. This is especially true for invasive fish, which can reduce the number of native fish and impact fishing livelihoods.

River project increases invasive fish spread

Recent research highlights concerns about India's River Interlinking Project, revealing potential threats to native fish species. The study indicates that through the project, invasive alien fishes are spreading to already inhabited areas, making almost 31% of the total area habitable for these invasive species.

Rivers like Pennar, Kaveri, Godavari, Krishna, and Mahanadi in central and southern India are particularly susceptible to invasions if interconnected. This interlinking could serve as a pathway for various species to travel, increasing the risk of invasive species entering areas with large lakes.

The implications for biodiversity preservation are significant. Invasive species pose threats such as competition for food, habitat degradation, and pollution, harming native biodiversity. The introduction of invasive fish can lead to a decline in native fish populations, impacting fishing resources.

Identifiers have recognized several invasive fishes, including Gambusia and Poecilia from the USA and South America. They have marked Pterygoplichthys as an ornamental fish, and identified invasive species like Tilapia and Cyprinus carpio in the river Ganga.

The River Interlinking Project aims to connect rivers through canals and reservoirs to manage water resources, reduce floods, and recharge groundwater. Approximately 18% of the world's population resides in India and uses about 4% of the world's water resources. Therefore, many see interconnecting rivers and lakes as a solution to address water challenges.

Study maps invasive fish distribution

The study modelled the current distribution of 12 alien fish species identified by Indian biodiversity authorities. These include species used for mosquito control, ornamental fish, and species grown in aquaculture farms.

The study showed that one species, Gambusia, has the highest area of occupancy. Another species, Pterygoplichthys, has the highest potential for range expansion in a changing climate. The researchers warn that linking certain rivers could make important biodiversity hotspots vulnerable to biological invasion.

India's National Water Development Agency under the Jal Shakti ministry manages the project, which comprises 14 inter-link projects for the Himalayan regions, 16 inter-link projects, and 37 intrastate river linking projects.

However, the study raises concerns about the ecological impact of interlinking rivers. The Subarnarekha-Mahanadi link and others connecting different river basins could expose threatened and endemic fish species to invasive ones.

The research team also projects future invasion patterns under different climate scenarios, suggesting a potential 2% reduction in niche suitability for invasive alien fish under the minimum greenhouse gas emission scenario and a 91% increase under the maximum emission scenario by 2100.

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