Fish use sharks as shields to ambush prey, study reveals

by University of Edinburgh
March 27, 2025

Scientists have revealed for the first time that some fish sneak up on their prey by hiding behind sharks.

The previously unknown behaviour was discovered by a team of researchers, including scientists from the University of Edinburgh, studying sandbar sharks in the Mediterranean Sea.

Underwater video footage captured by divers and remotely operated vehicles shows a type of small predatory fish – called blue runners – using the sharks for cover while they hunt. 

Previous research has shown that some fish shadow sharks to remove parasites and hide from predators. However, they have never before been seen hiding behind sharks to ambush their prey.

Videos captured off the coast of Italy’s Lampione Island revealed 34 examples of blue runners using this hunting strategy. On each occasion, a single fish shadowed a shark for around 30 seconds before breaking off to launch high-speed attacks on smaller types of fish, such as damselfish.

Analysis of the footage suggests that the fish – which usually hunt in small groups – are more likely to catch their prey off guard by shadowing sharks, increasing their chances of success, the team says. 

When hiding behind a shark, prey only noticed a blue runner’s approach around 10 per cent of the time. In contrast, when the fish hunted in packs their prey spotted them almost every time – more than 95 per cent of attacks – and got into a defensive schooling formation. 

Keep reading: https://www.ed.ac.uk/news/fish-use-sharks-as-shields-to-ambush-prey-study-reveals

Read the Ecology paper: https://esajournals.onlinelibrary.wiley.com/doi/10.1002/ecy.70028