Rising sea surface temperatures affecting fish distribution in Indian waters

Rising sea surface temperature (SST) is affecting fish distribution patterns in Indian waters, said JK Jena, Deputy Director General of Indian Council of Agricultural Research (ICAR).

He was speaking on India’s research initiatives for the climate-resilient marinefisheries at the inauguration of the global conclave on mainstreaming climate change into international fisheries governance in Mahabalipuram on Tuesday.

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Analysis of SST in Indian seas during 40 years (1975-2015) showed an increase of 0.60 degree celsius along the NE coast, 0.59 degree celsius along the NW coast, 0.697 degree celsius along the SE coast, and 0.897 degree celsius along the SW coast. The rate of change was highest in NW India, indicating greater climate-change impact along the west coast than the east coast, he said.

SST increase is affecting the spatial distribution and phenology of fish. This in turn is leading to fish maturing at smaller sizes. This means less reproductive output (less number of eggs) and less recruitment to the fishery. For instance, the Bombay duck is maturing early at a smaller size from 232 mm to 192 mm. Earlier, silver pomfret matured at a size of 410g, but now matures at 280g, he said.

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There is an extended distribution of commercially important fish species such as the Indian oil sardine and mackerel. “These species are now found in regions where they were previously scarce, forming a local fishery which was hitherto unknown from those areas”, he said. Mackerel fish are descending to deeper waters. It generally occupies surface and subsurface waters. However, in recent years, it is increasingly caught at about 50m depth, he added.

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Referring to India’s research initiatives for climate-resilient marine fisheries, Jena said that the country has initiated a research project for the development of species distribution climate models and projections. These models are designed to predict alterations in sea temperature, ocean currents, and other climatic elements that influence fish populations. This scientific initiative aims to comprehend long-term patterns and develop appropriate strategies to safeguard the future of Indian fisheries, Jena said.

The country has also launched a climate-smart marine fisheries value chain aimed at developing a prototype with critical control points to strengthen the value chain in the marine fisheries sector, he added.

Jena also highlighted a concerning trend of Harmful Algal Bloom (HAB) events in the Indian Ocean region. A three-fold increase in HAB events has been reported in the Arabian Sea during the last two decades, with 31 events, compared to the first two decades with 10 events. Similarly, the Bay of Bengal has seen a two-fold increase in HAB events, with 14 events in the last two decades compared to just 6 events in the first two decades, he added.

To reduce the impact of the climate crisis, Jena suggested mariculture activities of climate-resilient species encouraging the cultivation of fish species that can thrive in changing environmental conditions. “Use of potential fishing zones, integration of wind and solar energy in fishing vessels, enhancing preparedness of coastal population and sea ranching of depleted commercial species are some of the innovative solutions to address the climate crisis”, he added.

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