"When they are out in the open water they are actually quite sophisticated. They can swim well, they can smell, they can see, they can hear well, and they use a whole suite of senses," joint team leader Glenn Almany told Reuters.

Studying a tiny coral reef in Papua New Guinea, the researchers found 60 percent of baby clownfish find their way back to their home reef -- only 300 metres (1,000 feet) wide -- after being swept into the open ocean at birth.

The fish were identified using a world-first tagging method in which adult clownfish and butterflyfish were injected with a harmless barium isotope which they then passed on to their offspring, allowing identification of their juveniles.

The finding, announced in the international journal Science, will help researchers understand the extent to which young fish return to their home area or go off to interbreed with more distant populations. That in turn could help determine which populations needed protection or better management for sustainable fishing.

Almany said the team still had no idea how the clownfish knew which reef they came from, or how far they travelled in open sea during a journey lasting around 11 days.

"How they actually determine whether that reef is home or not is anyone's guess, but as an educated guess I would say that there might be some sort of chemical imprinting going on when they are born," he said.

The team of Australian, French and US scientists, working out of the Australian Research Council Centre of Excellence for Coral Reef Studies at Queensland's James Cook University, planned follow up studies in Australia with larger fish species.

Almany said researchers found a similar result to clownfish for butterflyfish, although the two species had very different breeding strategies. Clownfish adults closely guarded their eggs in a nest and butterfly fish gave no parental care to their offspring, which stayed at sea for around 38 days.