CHENNAI: Yes, as the adage goes, there’s plenty of fish in the sea. But, do we have a precise count? In literal terms, we soon may have an answer, as scientists and researches in India and across the globe are working on it. Experts are studying the floating bits of DNA in water samples, which they claim would reveal the relative biomass of fish in the sea.
The focus is now on environmental DNA (eDNA), to determine the variety of fish in an area of water. “eDNA-based monitoring will help create a profound impact on futuristic fisheries research and management,” said Dr P Jayasankar, former director of Indian Council of Agricultural Research (ICAR), Central Institute of Freshwater Aquaculture, and principal scientist, Central Marine Fisheries Institute.
This revelation comes in the wake of a paper published in the ICES Journal of Marine Science, which certificates ‘fishing for DNA’ as an inexpensive, harmless complements to nets, acoustics, and other established ways to monitor the health of fish stocks and the shifting diversity, distribution, and abundance of aquatic life.
The paper, as a product of collaboration between the Rockefeller University, Monmouth University, and the New Jersey Bureau of Marine Fisheries, said the information about the diversity and relative abundance of fish available in a one-litre sample is comparable to a 66 million litre trawl sweep, that is enough seawater to fill a football stadium to the top of the goalposts.
While eDNA has been proved earlier as a reliable tool to determine the variety of fish in an area of water, the new study is the first to show that bits of eDNA floating in seawater also disclose the relative abundance of the species swimming through it. Fish and other organisms shed dandruff-like DNA, leaving an invisible trail as they swim.
This eDNA can be skin cells, droppings, urine, eggs, other biological residues that last in the ocean for a few days, said Dr Mark Stoeckle, Senior Research Associate at the Rockefeller University Program for the Human Environment. “The applications of eDNA in the marine realm are vast,” Stoeckle said, who helped pioneer the ‘bar coding’, the identification of species from a small region of the animal’s DNA sequence.
Jayasankar said, “In India, the research is focussed on confined habitat, basically an aquarium, river or lake, where the gene flow is restricted and greater since 2017.Our efforts in Kumarakom backwaters show encouraging results. We have planned to further our study using an interactive GIS, a framework for gathering, managing, and analysing data. For now, Vembanad backwaters and Kavaratti island in Lakshadweep are targetted. Using imageries, sampling locations are identified based on bathymetry and geological considerations.
The experts say...
eDNA could reveal ecological effects of marine industrial activities, including offshore wind farms, oil and gas rigs, commercial fishing