Overfishing kills marine biodiversity

Overfishing kills marine biodiversity

Like its rich terrestrial biodiversity, India is equally rich in marine biodiversity. India’s coastline is more than 7,500km in length and extends to a total area of about 2, 81,600 sq km. It harbours unique habitats and a plethora of marine species. Despite logistic constraints in explorations and collection of specimen; the number of species known from the Indian coastline is more than 13,000.

The Indian coastal water harbours 451 species of sponges, more than 200 species of corals, more than 2900 species of crustacean, 3370 species of marine mollusks, more than 200 species of bryozoans, 765 species of echinoderm, 47 species of tunicates, more than 1300 marine fishes, 26 species of sea snakes, 5 species of sea turtles and 30 species of marine mammals including dugong, dolphins, whales, etc. In addition a wide variety of sea birds can be observed around the coast.

But unfortunately, habitat and biodiversity loss due to bottom trawling, overfishing, use of small sized mesh nets, juvenile fishery etc. are wrecking havoc on marine biodiversity of India. About 72 per cent of total production of marine fish in India, lands at the West Coast. Kerala is the biggest producer followed by Maharashtra, Karnataka, Gujarat, Goa, Daman and Diu.

Kerala has a long coastal line of 590 km on the western side of the state hugging the Arabian Sea. The marine, brackish and freshwater fisheries are important for the state’s economy. For a biologist, the Ramsar convention wetlands, mangrove forests and marine biodiversity of Kerala serve as a natural laboratory.

Massive turnover

The domestic turnover in fishery sector is about Rs 6,000 crore and provides livelihood for 1.7 million people in Kerala. Foreign exchange turnover of the state through the export of marine product accounts for more than 20 per cent of the total marine export earnings of the country. At the same time crores of rupees are lost due to large scale fish massacre in the Arabian Sea. More than 100s of tons of small fishes are drained daily from the sea using small mesh nests and sent to the factories in Mangalore. There it is dried and powdered to make organic manure and fish feed. Fishmeal from Mangalore reaches Japan via Colombo in 20 to 25 days.

A large net called trawl is towed along the sea bottom by one or more boats, called trawlers or draggers. Bottom trawling results in a lot of by-catch and can damage the sea floor. A single pass along the seafloor can remove 5 per cent to 25 per cent of the seabed life. From the Munambum harbour of kerala itself more than 40 tones of small fishes are harvested like this. This will make the sea barren and lead to severe shortage of fishes.
The fingerlings of leather jacket fishes are mostly captured.

Besides crabs, prawns, lobsters and squids; the young ones of Sardine, Mackerel, Threadfin Bream, and Milk Fish etc. too get entangled in the small mesh nests. Along with this so many other inedible biota too are captured. This in turn completely smashes up the marine ecosystem.

These small fishes are sold just for Rs10 per kilogram. There is large scale removal of fingerlings from Beypore, Neendakara, and Shakthikulangara harbours. The leather jacket which grows up to 2.5 kg has a market value of Rs 150 per kg. It has good demand abroad and has an export value of 6 dollars. Thousands of tons of leather jackets below 25 gm weight are drained from the sea in the past one month in these areas. Fishes which can grow hundred fold weights and yield good foreign money is being crushed and made manure and fish feed.

Fishermen who go in big trawlers exhaust small fishes using odd nets. They catch it as an extra source of income. Traditional fishermen leave small fishes back into the sea. Perverse subsidies in fishing industries are incentives to fishermen to overfish. Various aspects of coastal ecosystems- the environmental process, functioning, flow of marine resources and various conflicts are to be mulled over before drawing a strategy of marine diversity conservation.

Proper legislative measures, socio-economic analysis and integrated management practices of marine and surrounding terrestrial areas are required to develop a sound marine biodiversity conservation strategy.