Have you ever wondered why some summers feel warmer than others? Or why some winters feel bitterly cold compared to last year? Well, the phenomenon known as the El Niño-Southern Oscillation (ENSO) is likely at least partly to blame.

ENSO is a natural climate pattern in the tropical pacific which drives local and global weather patterns. Shifting between three distinct phases – El Niño, La Niña, and Neutral – the pattern fluctuates every 2 to 7 years, influencing rainfall, storms and weather.

El Niño is characterised by warmer ocean waters in the central and eastern pacific, resulting in weakened trade winds, resulting in drought and heightened bushfire risk in Australia, and cooler, wetter conditions in the southern USA and Mexico. La Niña is characterised by cooler than average sea surface temperatures and stronger trade winds, causing upwellings of cold water near the Americas and rain and flooding in Australia.

Each year, the Bureau of Meteorology (BOM) report on the current status of ENSO and provide forecasts using climate models. In 2026, the BOM models are predicting an El Niño by late winter. This event is expected to peak between late October and November 2026, with warmer than average sea surface temperatures forecasted from May to July. 

Furthermore, some forecasters are predicting that the 2026 El Niño may be a ‘super El Niño’. The last super El Niño was in 2015/16. In general, super El Niños last longer, push warmer water farther east, more strongly impact tradewinds and produce larger influences on global weather patters.

So, what does this mean for Australia’s oceans and our seafood sector?

On the north eastern coast of Australia and the Great Barrier reef, previous El Niño events have been associated with coral bleaching events on the Great Barrier Reef. Along the east coast, fish recruitment can be higher during El Niño years for some species as warmer water pulls tropical species further south. However, El Niño results in a reduction in rainfall over eastern Australia, which means less freshwater and terrestrial nutrient runoff into estuaries and coastal zones for inshore fisheries.

In the south east, including the coasts of southern New South Wales, Victoria and Tasmania, an El Niño event can cause intensification of the southward extension of the East Australian Current, causing out-of-range observations of several fish species, including yellowtail kingfish, snapper, dusky morwong, mahi mahi, blue moki and moonlighter fish – unusual sightings can be reported via platforms like Redmap, the Range Extension Database and Mapping Project.

Along the coast of western Australia, the Leeuwin current weakens during El Niño events, causing ocean temperatures to fall. This can change the distribution of fish species, the transport of rock lobster larvae, and can affect seasonal migrations of whale sharks and seabird breeding success. Historically, western rock lobster recruitment has increased during stronger Leeuwin Current years, so El Niño years tend to bring weaker recruitment. There’s also a rainfall link: rapid changes in salinity during the onset of El Niño may affect the abundance and distribution of fish species in rivers, estuaries and bays around southwest WA.

The impacts of El Niño on the south Australian coast are less clear. The eastern Great Australian Bight receives seasonal upwelling of deep ocean water along the Eyre Peninsula, creating an important marine productivity hotspot. El Niño may enhance summertime upwelling along the SA coast, meaning nutrient delivery to surface waters could increase, but the effect is modulated by both local winds and remote signals from the west Pacific.

ENSO doesn’t act alone. Several other climate systems, including the Indian Ocean Dipole and the Southern Annular Mode, interact with it to determine what any given season actually looks like for Australia’s oceans. And with climate change raising baseline ocean temperatures year on year, the effects of El Niño events on our marine environment are only expected to intensify.

How can you stay informed and help monitor ENSO in Australia? 

To monitor the ENSO status in Australia, be sure to keep updated on the BOM Southern Hemispehere Monitoring, and monitor the BOM marine heatwave forecasts.

If you would like to know more about El Niño and how it could impact your region, your fishery or your seafood operations, reach out to the Sea Change Australia team via out Q&A platform, and we will reach out to key experts to response to you directly.

Lets continute to talk about climate change and help each other be better prepared for changes in climate and extreme weather events into the future.