Coastal seas in an El Niño year: marine heatwaves and fishing communities

El Niño does not only affect rain on land. It also warms the seas around India, and that matters for fish, coral and the people who depend on them.

What is a marine heatwave? INCOIS, the Indian National Centre for Ocean Information Services under the Ministry of Earth Sciences, defines levels by how far the sea surface is above the 90th percentile of normal temperatures for that day: Watch (0–0.5°C above), Alert (0.5–1°C above) and Warning (more than 1°C above).

What INCOIS saw on 2 October 2026.

• Arabian Sea: 20% of the area under Watch, 34% under Alert and 11% under Warning, along India's west coast off Maharashtra, Goa, Karnataka and Kerala and around Lakshadweep. Possible impact: marine productivity and coral reefs.
• Bay of Bengal: 28% Watch, 11% Alert and 1% Warning, along the coasts of West Bengal, Odisha, Andhra Pradesh, Tamil Nadu and the Andaman and Nicobar Islands. Possible impact: coastal ecosystems.

The El Niño link. In August, the Ministry of Earth Sciences said El Niño may raise the chance of marine heatwaves in the Arabian Sea and Bay of Bengal, affecting where fish are found.

For fishing communities. INCOIS publishes daily marine heatwave advisories on its website and separate marine fisheries advisories. Check them before planning trips, and follow your state fisheries department's guidance.

Join the El Niño help room on soshyal.com to ask questions and share what you see in your area.