In the heart of India’s Eastern region, a silent invader has been making waves, quite literally. The Nile tilapia (Oreochromis niloticus), a fish native to Africa, has been rapidly spreading across the freshwater habitats of West Bengal, posing significant threats to native biodiversity and the sustainability of local fisheries. But now, scientists have a new tool in their arsenal to track and manage this invasive species: environmental DNA (eDNA).
A recent study, led by Basanta Kumar Das from the Aquatic Environmental Biotechnology Division at the Indian Council of Agricultural Research (ICAR)-Central Inland Fisheries Research Institute in Kolkata, has demonstrated the power of eDNA analysis in mapping the distribution of Nile tilapia across various aquatic habitats. The research, published in the journal ‘Frontiers in Marine Science’ (which translates to ‘Frontiers in Ocean Science’), offers a promising approach to invasive species monitoring that could have significant implications for fisheries management and biodiversity conservation.
eDNA analysis involves detecting the genetic material that organisms leave behind in their environment, such as in water or sediment. This non-invasive method allows scientists to assess the presence and distribution of species without the need for traditional survey methods, which can be time-consuming and often disturb the ecosystem.
In this study, Das and his team used species-specific primers to amplify eDNA signatures from both sediment and direct tissue samples. The results confirmed the widespread presence of Nile tilapia across multiple habitats, with sequences submitted to the National Center for Biotechnology Information (NCBI) for reference. The study also highlighted the influence of environmental factors on eDNA persistence and detection efficiency. “We found that temperature, pH values, and sediment composition played crucial roles in eDNA stability,” Das explained. “For instance, sand-dominated substrates facilitated rapid DNA percolation and loss, whereas finer sediments enhanced retention.”
The findings also underscored the importance of habitat-specific sampling strategies. While eDNA was successfully amplified in lentic environments (such as ponds and lakes), it was notably absent in high-flow systems like the Ganga River and certain other locations. This absence could indicate low species abundance or rapid DNA degradation in such dynamic environments.
The commercial impacts of this research are substantial, particularly for the fisheries sector. Invasive species like the Nile tilapia can outcompete native fish for resources, leading to declines in local fish populations and affecting the livelihoods of those dependent on fisheries. Accurate and efficient monitoring tools, such as eDNA analysis, can help fisheries managers and conservationists implement targeted mitigation strategies to control invasive species populations and protect native biodiversity.
Moreover, the integration of eDNA-based monitoring into global invasive species management frameworks could revolutionize how we approach biodiversity assessment and conservation. As Das noted, “This study establishes eDNA as a powerful, non-invasive tool for invasive species monitoring, bridging molecular ecology with conservation management.”
Looking ahead, the research team advocates for further refinement of molecular protocols, integration of hydrodynamic modeling, and optimization of eDNA sampling methodologies to enhance surveillance accuracy. These advancements could pave the way for more effective invasive species management strategies, not only in India but globally.
In an era where invasive species pose an ever-growing threat to ecosystems and economies, the work of Das and his team offers a beacon of hope. By harnessing the power of eDNA analysis, we can better understand and manage invasive species, ensuring the sustainability of our precious aquatic ecosystems for generations to come.