Sri Lankan fishermen have been catching fish for the last four decades from the popular harbor on Sri Lanka’s west coast, Negombo. In the past five years, the catch has been dwindling posing a livelihood crisis. Fisherman complains that they are spending out more and more time in the high seas with the catch falling continuously.
Most fishermen carry out the fishing on trawlers on multi-day trips and venturing as far as 100 to 150 kilometers from the shores.
Overfishing could be a possible cause, but a more important reason is the warming of the Indian Ocean due to global warming.
Roxy Mathew Koll, a scientist at the Centre for Climate Change Research at the ‘Indian Institute of Tropical Meteorology’ in Pune said that rapid warming of the Indian Ocean has led to up to 20% fall in the phytoplankton population in the ocean.
Phytoplankton is a major contributor of oxygen on the planet. The past decades has seen a steady decline in the phytoplankton population in the oceans around the globe.
Phytoplankton population happen to be at the base of the ocean food chain and are available as food for fish. So the reduction in phytoplankton concentration in the oceans will also lead to a fall in the fish population. Scientists around the globe have also endorsed this fact.
Koll warns that the fall in levels of phytoplankton in the seas will have a disastrous effect and could change oceans from biologically productive regions in ecological deserts. It will have a devastating impact on world fish supply especially in China and South East Asian nations where fish is an inalienable part of daily diet.
One of the reasons propagated by oceanologist for the fall in phytoplankton is the warming of Indian Ocean by 102 degrees Celsius, which have slowed the missing of surface water and the nutrient-rich deeper waters.
The mixing of the nutrient-rich deeper water with the warmer surface water where light is available for photosynthesis is crucial for the growth of phytoplankton.