Mumbai has highest concentration of non-biodegradable marine debris
ICAR-Central Marine Fisheries Institute revealed debris found by trawler nets in the fishing grounds off Mumbai is 49.11kg per square kilometre
Each time polythene covers, carry bags, or synthetic packaging materials are carelessly dropped on the streets or disposed into open drains, creeks and rivers, the wind and rain carry these trash into the sea as run-offs. Additionally, plastic litter strewn on beaches becomes brittle under hot and humid conditions, and settles on the sea bed in the form of micro plastics and nanoplastics.
While the sea throws some of the non-biodegradable marine debris back on to the land, the initial results by ICAR-Central Marine Fisheries Institute (CMFRI) revealed the highest average concentration of non-biodegradable marine debris (NBMD) found by trawler nets in the fishing grounds off Mumbai at 49.11kg per square kilometre (sq km). Second in line is Tamil Nadu’s Tuticorin coast with an average concentration of 37.06 kg/sq km followed by 19.9kg/sq km in Ratnagiri. The lowest concentration is at Vishakhapatnam with 2.25 kg/sq km) .
A 2015 study led by the University of Georgia ranked India 12th among the top 20 coastal populations (and 192 countries) in the world that sent 0.60 million tonnes per year of mismanaged plastic waste into the ocean.
“This is baseline data set where we wanted to highlight that non-biodegradable marine debris is increasing from south to north in the west coast, whereas it’s reverse in the east coast,” said P Kaladharan, principal investigator, CMFRI.
“This database is important in the light of increasing deleterious effects of plastic pollution in sea and the urgent need to protect the sea for sustainable fishing.”
High concentration of plastic marine debris in the fishing grounds also has an impact on the fish catch. A September 2017 study found that the relative percentage of marine debris to the overall fish catch was the highest in Mumbai and Kochi at 2.23% as compared to 0.33% off Vishakhapatnam coast.
“The problem of plastic accumulation in the sea is going to increase in the future unless the use of plastic is controlled on land, as most enter into the sea through run-off. Plastic materials in the fishing gear could also get lost during fishing operations,” said E Vivekanandan, consultant and scientist, CMFRI.
But it’s not just plastic that is polluting our seas. The problem gets manifold with marine debris in the form of abandoned, lost or discarded fishing gear (ALDFG) that could either be as a result of fishermen cutting their nets or natural disasters such as cyclones. Both these situations affect marine life with reports of turtles entangled in ghost nets in the Arabian Sea and Bay of Bengal.
While there are no exact estimates on the contribution of derelict fishing gear for Mumbai, a study across six beaches in Kerala last year showed that fishing-induced debris contributed to 26% of the total beach litter.
Scientists said the loss of fishing gear has become a serious problem with a transition using natural biodegradable materials such as cotton, hemp, coir, wood that can disintegrate within a short time span to non-biodegradable non-synthetic materials such as polythene and nylon, which can stay in water bodies for up to 600 years.
In 2017, the Indian Council of Agricultural Research-Central Institute of Fisheries Technology estimated that of the 60,000kms of netting that are deployed by gillnet vessels, 6,000 kms is likely to be lost in the sea. This is based on the projection by Food and Agriculture Organisation of the United Nations that average loss of gillnets is 10% every year.
“Fishing nets are cut when they get entangled with rocks in fishing ground. Sometimes old nets are used which also get torn in the sea, and fishermen abandon them,” said Vivekanandan.
He added, “We need short term and long term solutions to curb plastic use in the form of clean-up drives, educational programmes, public awareness on not releasing plastic and bottles in the open landscape. Long term solution should focus on the bringing down plastic production with the government laying out a plan to introduce alternatives to it.”