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

The previously unknown behavior 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鈥攃alled blue runners鈥攗sing 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鈥攚hich usually hunt in small groups鈥攁re 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% of the time. In contrast, when the fish hunted in packs, their prey spotted them almost every time鈥攎ore than 95% of attacks鈥攁nd got into a defensive schooling formation.

As well as improving their chances of a successful hunt, the shadowing behavior may protect blue runners from their own predators and help them conserve energy by swimming in sharks' slipstream, the team says.

The research is based on multi-year observations around Lampione Island, where a rare clustering鈥攌nown as an aggregation鈥攐f sandbar sharks occurs every summer.

The study is in the journal Ecology. It also involved researchers from Stazione Zoologica Anton Dohrn, the National Biodiversity Future Center, CNR-IAS and the University of Palermo.

Professor Fabio Badalamenti, of the University of Edinburgh and CNR-IAS Palermo, said, "The study highlights how interactions between species can drive alternative hunting tactics in marine ecosystems. Understanding these dynamics enriches our knowledge of marine biodiversity and underscores the importance of conserving high-level predators, like sharks."

Dr. Carlo Cattano, of the Stazione Zoologica Anton Dohrn, said, "This unique interaction emphasizes the ecological importance of the few remaining shark aggregations, which can influence the structure and function of ecosystems. Lampione Island is one of only two known aggregation areas for the sandbar shark in the Mediterranean Sea. The ongoing decline in large shark populations due to overfishing could jeopardize associations like these, which could have knock-on effects on other species."