Saturday, January 09, 2010

Fish bounty hope after Aila churns bay

Cyclone Aila, which left a trail of death and destruction in Bengal in May last year, may lead to a boost in fish catch in eastern India over the next few months, a top ocean scientist said today.

Shailesh Nayak, secretary with the ministry of earth sciences, told a gathering at the 97th Indian Science Congress that the cyclone which killed nearly 140 people and affected 65 lakh in Bengal, caused an unprecedented spurt in the production of a marine organism which forms the bottom of the aquatic food chain.

"Following the cyclone, the production of phytoplankton (microscopic plant-like marine organisms) doubled in the Bay of Bengal," Nayak said. This bloom that lasted a month was spread over an area of 3,000sqkm in the Bay of Bengal, he said.

While such algal blooms are commonly observed in India's western coast, it rarely happens in the Bay of Bengal because its waters are highly compartmentalised. As a result, there is a limited scope for the circulation of the nutrient-rich water from the bottom to the surface and vice versa.

The algal bloom may have beneficial effects on fish catch from the sea, fishery experts said. "Fish availability increases considerably after a phytoplankton boom," said B. Madhusoodana Kurup, the director of the school of industrial fisheries at the Cochin University of Science and Technology in Kerala. This is because phytoplankton are eaten by another set of marine organisms called zooplankton which forms the feed for fish. When zooplankton are abundant in the spawning season, fish production goes up, Kurup said.

Such a spurt in potential fish production is normally witnessed six months to 18 months after the phytoplankton boom, depending on the type of fish harvested from a particular area. Considering that some of the prominent marine fish varieties harvested in Bengal are perch, mackerel and carangid, the effective increase in yield can be expected one year to 18 months after the disaster, he said.

Nayak said a passing cyclone triggers a churning process in the ocean, which in turn brings up the nutrients lying at the bottom of the sea surface. The increase in nutrient availability prompts the plankton to work overtime to produce more.

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