Understanding heavy metals in commercially traded rays in coastal West Bengal
Along India’s Bay of Bengal coast, rays are caught at busy landing sites such as Digha and Fraserganj. They are traded and consumed locally with little limiting their exploitation. This coastline also receives heavy pollution from upstream industries, agriculture and urban waste. Mercury, cadmium and lead enter the sea and accumulate in marine animals. Nidhi worries about the sustainability of overfished ray populations, but also about the risk that their consumption may pose to people. She’s analysing ray tissues, conducting community surveys and sharing her results with fishers, consumers and policy-makers to raise awareness of the risks and encourage reduced consumption of threatened species.
Nidhi Johri
I grew up in North India, far from the coastline but with a strong fascination for the sea and the creatures that inhabit it. That interest led me to pursue a Master’s degree in marine science, specialising in marine biology, and to continue with a PhD in environmental studies at Ashoka University. My work has taken me to fishing harbours along the Bay of Bengal, where I have spent countless hours documenting sharks and rays as they are landed and traded.
Over the years, I have become particularly focused on rays, animals that are ancient and...
Assessment of Heavy Metal Bioaccumulation in Commercially Traded Rays in Coastal West Bengal
The main aim is to measure levels of toxic heavy metals in rays landed in West Bengal, India, and show how this affects both human health and the conservation of these threatened species.
Rays are among the most vulnerable marine animals, yet they are still caught and consumed in large numbers in India. Many of these species are threatened with extinction and they may also carry dangerous levels of toxic metals like mercury and lead. By showing that eating these rays is unsafe for people, this project aims to reduce demand for their meat and create stronger reasons to protect them.
Rays, like sharks, are slow-growing animals that mature late and produce few offspring. These traits make them highly vulnerable to overfishing, and across India they are landed in large numbers, even though many species are classified as threatened. Along the Bay of Bengal coast in West Bengal, rays are an important part of the catch at busy landing sites such as Digha and Fraserganj. Here, they are sold for local consumption and trade, with little regulation to limit their exploitation.
At the same time, this coastline receives heavy pollution from industries, agriculture and urban waste upriver. Toxic metals such as mercury, cadmium and lead enter the sea and accumulate in marine animals, especially those higher up the food chain. Studies elsewhere in India have already shown that sharks and rays can carry unsafe levels of these contaminants. This means that their consumption may pose serious health risks to people, particularly in fishing communities that rely on them for food.
This project will be the first to assess contamination in rays along West Bengal’s coast. By linking public health concerns with conservation, it seeks to change how these species are valued and create momentum for stronger protection.
- To collect and analyse ray tissue samples from two major landing sites in West Bengal to measure levels of mercury, cadmium, lead, copper and zinc.
- To conduct community surveys to understand how often rays are consumed and estimate the health risks posed by contaminated meat.
- To share results with fishers, consumers and policy-makers in order to raise awareness of the risks and encourage reduced consumption of threatened species.
- To provide evidence that can support seafood safety advisories and conservation-oriented fisheries management.