Tuna feeding frenzy

Описание: In September (8/9/2025), a phenomenon called 'boiling sea' was recorded in Alderney's waters. It is caused by large numbers of bluefin tuna hunting together in a feeding frenzy.

The tuna round up prey fish into large shoals, called bait balls, which they then charge into. They force the bait balls to the surface to stop their prey escaping and this activity attracts thousands of seabirds, including gannets and herring gulls, which then feed on the prey fish from above.

Seeing tuna feeding in these numbers would have been commonplace in the past, before industrial fishing decimated fish stocks, and it is amazing to see our seas beginning to recover.

This awe-inspiring display of nature in action is an example of how the return of an apex predator like tuna can have huge benefits for a wide range of species. Alderney's seabirds are under pressure from climate change and are forced to fly further and further in search of food each year. With the tuna creating these feeding opportunities the seabirds have a chance to feed closer to their nesting sites meaning they can bring more food back to their chicks.

When the prey fish have escaped or been eaten, the tuna disappeared into the turquoise water, while the seabirds rest on the surface, ready for the tuna to corral more prey into the next bait ball. As apex predators, the tuna fill an important roll in the marine ecosystem, like that of lions in the Serengeti or a peregrine falcon on the coast.

Tuna have been recorded migrating through Alderney’s waters for the last few years, but this is one of the only occasions when a feeding frenzy has been filmed from above. The footage was captured by a drone flying at a safe distance of at least 50 metres from the wildlife. You can read about some fantastic tuna research from the Channel Islands following this link: https://www.gov.je/SiteCollectionDocuments...
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Footage by Alex Purdie
Text: Thanh Doan and Alex Purdie
Video editor: Thanh Doan
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