A tiny, oily fish is TikTok's latest obsession. Is there a catch?

Walk down the canned fish aisle at your local supermarket right now, and there's a good chance you'll find a gap where the tinned sardines used to be, as a viral TikTok trend sends a wave of new fans in search of the small, oily fish.

The trend, dubbed "sardinemaxxing", has seen influencers push sardines as a beauty and wellness must-have, with some calling them "Botox on a fork" for their purported skin, hair, and anti-ageing benefits.

But experts say the trend raises real questions about where those sardines are coming from — and what happens if the hype spreads to other seafood.

Sardines are just the latest grocery item swept up in a social media-driven buying frenzy.

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Cottage cheese and Greek yoghurt both had their moment in the past year, part of a broader "proteinmaxxing" wave prizing high-protein foods.

Lisa Asher, a retail and supermarket expert at the University of Sydney Business School, said the pattern is driven by a mix of influencer culture and wellness trends.

"What bothers me isn't that the kids are eating sardines … it's that they're taking advice now from people who are probably not people you should be listening to," Asher said.

"It's a new form of advertising with a lot of unknowns — we don't really know who's paying who and how much they're making out of it. That is a problem.

"In magazines, we used to look at celebrities, but celebrities have been replaced by influencers."

She said the trends all follow a similar pattern: demand increases, the product goes out of stock, prices sometimes rise, and eventually, when the hype cools down, it comes back in stock.

"But this is a product that is made from fish in the sea," she adds. "We don't want to overfish because suddenly, then we have none."

Adrian Meder, sustainable seafood program manager at the Australian Marine Conservation Society, says history shows a sudden cultural appetite for a particular seafood can do serious damage — pointing to shark fin soup, sea cucumber and some tuna fisheries as species pushed towards collapse by surging demand.

"We've yet to see online popularity as a driver of major declines in our oceans, but a cultural surge in popularity of a seafood has time and time again decimated populations of species from tunas, to sharks, to abalone, to sea cucumbers," Meder told SBS News.