Clownfish, known to spend much of their lives among the protective tentacle shroud of host anemones, take to open waters when young and can travel hundreds of miles, says surprising new research.

The study of the dispersal of Omani clownfish larvae found that six percent of the fish sampled had migrated over 250 miles, or 400 kilometers, which can only happen during the larval stage, when the young critters can be swept away by ocean currents, according to a university news release.

Although the process of long-distance dispersal by reef fish has been predicted by prior research, explained study lead Steve Simpson, a senior lecturer in marine biology and global change in biosciences at the University of Exeter in England, the latest work represents the first time that such an extensive exchange of offspring between distant populations has been observed.

Simpson and colleagues from the Australian Research Council Centre of Excellence for Coral Reef Studies, Sultan Qaboos University in Oman and the Centre National de la Recherche Scientifique in France have published their findings in the journal PLOS ONE.

"This is an epic journey for these tiny, week-old fish. When they arrive at the reef, they are less than a centimetre long, and only a few days old, so to travel hundreds of kilometres they must be riding ocean currents to assist their migration," said Simpson, who directed a team of undergraduate and postgraduate students from the University of Edinburgh in Scotland to collect clownfish samples from throughout southern Oman.

"The southern coast of Oman is relatively isolated from the rest of the Arabian Peninsula so you find a lot of species there that you wouldn't find anywhere else in the world," Simpson explained. "There are only two coral reef systems along this coast, and they are separated by 400 km of surf beaches. In order to persist as a single species, we know Omani clownfish fish must occasionally migrate between these two populations."

The team used DNA identification methods to determine local, long-distant migrant, and hybrid individuals from populations throughout the entire Omani clownfish (Amphiprion omanensis) species range.

Around 400 fish were harmlessly caught during 92 dives, with a small fin clip obtained from each or DNA analysis before the fish were returned to their colonies.

"Just like accents that allow us to tell an Englishman from an American, fish populations develop their own genetic signatures," said co-author Hugo Harrison from the Australian Research Council program. "By looking at the signature of each fish we can tell whether it originated there or not. It's like finding an Englishman in New York, they stand out."

Prevailing evidence indicated the majority of migrant fish had traveled from north to south and that "the pattern of migration corresponded to the dominant ocean currents in the region that are driven by the winter monsoon," said co-author Michel Claereboudt from Sultan Qaboos University.

As well as migrants, second generation hybrids were also identified in both populations, showing that after dispersal migrants had joined and reproduced with local populations.

"This study is the furthest anyone has tracked the dispersal of coral reef fish, and it demonstrates that distant populations in the marine environment can be well connected," said Simpson. "Our ability to predict how far fish larvae disperse helps us to manage coral reef ecosystems. Understanding connectivity means we can protect populations that are most sensitive, harvest from populations that have a regular and consistent turn-over, and design coherent networks of marine protected areas."