Kolkata: A species of mangrove grass, which has so far been left unused by islanders in the Sundarbans, can now be utilised to prepare a cheap and eco-friendly feed for freshwater prawns, a team of scientists from Kolkata has recently demonstrated.
To prove how floral feed can offer better aquaculture nutrition and eco-friendly prawn farming, a pilot project led by Calcutta University`s marine biologist Abhijit Mitra was executed at Swarupnagar village of North 24 Parganas district, few kilometres from here.
Mitra said the formulated feed from salt marsh grass Porteresia coarctata, available naturally in the Sundarbans, not only improves the aquatic health of ponds but also increases the growth and protein level of Macrobrachium rosenbergii, a species of prawn.
It is estimated that annually India produces over 30,000 tonnes of the giant fresh water prawn, the export prices of which range between Rs 500-600 a kg.
Prawns reared on floral feed exhibit greater weights and redder colouring (both attributes with high consumer appeal), and grow more quickly than those surviving on commercial feed.
Besides mangrove grass, the other ingredients of the scampi feed preparation includes soybean dust, muster oil cake, rice bran and wheat bran.
"If adopted by the people of Sundarbans, the technology can aid their livelihood. Presently they are buying an imported commercial feed which costs them Rs 52 per kg but this new herbal feed will cost them only Rs 28," Mitra told PTI.
Besides using these feed at their ponds, farmers can also sell the feed itself to other aquaculture farmers.
"Our investigation also shows that prawn farming in the freshwater system of Indian Sundarbans is an economically feasible project and the return can be enhanced if specially formulated herbal feed is provided to the culture species instead of the traditional one," says the biologist.
Other researchers in the project included scientists Sufia Zaman and Subhrabikas Bhattacharyya.
Besides being economical, the new herbal feed also has ecological benefits as it produces less waste and so helps to improve water quality.
"Commercial feed contains trash fish and shrimp dust as a source of protein. The residual commercial feed degrades water quality by increasing the organic carbon, nutrient load, biochemical and chemical oxygen demand, and total coliform bacteria," says Mitra.
As the water quality of the pond is enhanced, it also removes the need to clear mangroves for wastewater removal systems such as canals and ditches.