Baby Fish Are Carrying Stinging Anemones Like Tiny Bodyguards—And Scientists Are Amazed

How Juvenile Fish Use Anemones as Living Shields in the Open Ocean

Deep in the inky blackness of the open sea, a nightly spectacle unfolds: millions of sea creatures rise from the depths to feed under cover of darkness. Among them are tiny, silvery juvenile fish—some no bigger than a fingernail—doing something scientists never expected: carrying stinging anemones in their mouths like portable bodyguards.

This startling behavior, recently documented in a study published in the Journal of Fish Biology, was captured not by lab equipment or submersibles—but by blackwater divers armed with little more than cameras and curiosity.

What Are Blackwater Dives?

Blackwater diving is a specialized form of night diving done far offshore, where divers drift with ocean currents while shining lights into the water column. The technique reveals a hidden world of larval creatures, gelatinous zooplankton, and translucent baby fish rarely seen by human eyes.

“You’re just out there drifting with the current and checking out all this life that’s in the ocean,” said Rich Collins, a blackwater photographer affiliated with the Florida Museum of Natural History. His images—along with those from fellow divers—became the foundation for the new research.

Young Fish + Stinging Anemones = Survival Strategy?

The study, led by Gabriel Afonso, a doctoral student at the Virginia Institute of Marine Science, analyzed dozens of high-resolution photos showing juvenile fish from families like pomfrets and filefishes holding larval sea anemones—close relatives of jellyfish—in their mouths or hovering just behind them.

Unlike adult anemones that cling to rocks or coral, larval anemones float freely in the open ocean. And like their adult counterparts, they possess stinging cells called nematocysts—capable of deterring or even injuring would-be predators.

“The fish sometimes seem to be using the invertebrate as a protection,” Afonso said. “It’s like carrying a weapon you didn’t build—but can still use.”

Four Fish Families Observed in This Symbiotic Behavior

Researchers identified interactions between larval/juvenile fish and anthozoans (the class that includes anemones and corals) across four distinct fish families in the pelagic zone—a rare find, given how little is known about early marine life stages.

Bramidae (pomfrets)
Monacanthidae (filefishes)
Stromateidae (butterfishes)
Carangidae (jacks and pompanos)

Each image showed the fish positioned deliberately near or holding the anemone—suggesting this isn’t accidental, but a calculated survival tactic in a predator-filled ocean.

Why This Discovery Matters

For decades, marine biologists assumed that such symbiotic relationships only occurred near reefs or the seafloor. Finding them in the open ocean—where shelter is nonexistent and danger is constant—rewrites part of the playbook on how marine life survives its most vulnerable stages.

“These early life phases are a black box,” Afonso explained. “We lose so many young fish to predation. If they’re actively seeking out defensive tools like anemones, it changes how we model survival, migration, and even fisheries management.”

Citizen Science Meets Cutting-Edge Research

Perhaps most remarkably, this breakthrough came not from a government-funded expedition, but from citizen scientists and underwater photographers sharing their observations with researchers.

Collins and others have spent years documenting blackwater life, often posting findings to marine biology forums or directly collaborating with institutions like the Florida Museum of Natural History. Their contributions are now proving invaluable to science.

What’s Next?

Scientists hope to use underwater drones and DNA barcoding to confirm whether the anemones are actively “handed off” between fish or simply grabbed opportunistically. They’re also exploring whether this behavior is learned or instinctual.

One thing is clear: in the vast, dark theater of the open ocean, even the smallest players have evolved astonishing tricks to stay alive.