Flirting with the enemy: fish using sharks to exfoliate

The fish in this video aren’t snuggling with sharks – they are exfoliating.

A team of researchers from the University of Miami, US, documented 47 instances of fish getting up close and personal with the enemy by rubbing against sharks – some even dared to rub against great whites.

“While we don’t exactly know why it’s happening, we have a few theories,” says research associate professor and study co-author Neil Hammerschlag.

“Shark skin is covered in small tooth-like scales called dermal denticles, which provide a rough sandpaper surface for the chafing fish.

“We suspect that chafing against shark skin might play a vital role in the removal of parasites or other skin irritants, thus improving fish health and fitness.”

The videos and reports were captured by drones, underwater cameras and witness reports in 13 different locations around the world, with the number of fish exfoliating against a single shark ranging from one to more than 100 at a time. The boldest of fish even chafed against the shark’s nose.

The researchers also found an instance of silky sharks chafing against a much bigger whale shark.

“While chafing has been well documented between fish and inanimate objects, such as sand or rocky substrate, this shark-chafing phenomenon appears to be the only scenario in nature where prey actively seek out and rub up against a predator,” says graduate student Lacey Williams, who co-led the study with fellow graduate student Alexandra Anstett.

The authors suggest that the ‘shark day spa’ plays an important ecological role in maintaining fish health, without which their skin and scales could be eroded by bacteria or other parasites.

The research was published in Ecology.

The Royal Institution of Australia has an Education resource based on this article. You can access it here.

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