Nemo The Clownfish Really Does Ride The World's Ocean Currents

A clownfish.

Baby clownfish are able to travel to new colonies hundreds of kilometres away just like the fictional film character Nemo.

Reseachers found that the amount of migration depended on the strength and duration of a seasonal ocean current.

They say these hardy travelling behaviours could make the fish better able to cope with environmental change.

Clownfish spend their adult lives under the protection of their host anemone but as babies they must wander the open ocean, says study co-author, Dr Hugo Harrison at James Cook University.

“In the past we haven’t known where they go, but now we’ve been given a rare glimpse into how far they can swim, crossing large tracts of ocean to find new homes,” he says.

“Knowing how far larvae disperse helps us understand how fish populations can adapt to
environmental changes.

“The further they can swim, the better they can cope.”

As part of the international study, co-author Dr Stephen Simpson from the University of Exeter led a team of researchers to southern Oman where they collected samples of the only two known populations of the Omani clownfish, Amphiprion omanensis.

“There are only two coral reef systems along this coast and they are separated by 400 kms of ocean water,” Dr Simpson says.

“In order to persist, fish must be migrating between these two populations.”

The research team collected tissue samples from almost 400 clownfish and used DNA fingerprinting to identify fish that had migrated between the two populations.

“Like the accents that we have that allow us to tell an Englishman from an American, fish
populations can develop their own genetic signatures,” says Dr Harrison.

The study found the fish were making regular migrations from one population to another and in
doing so were travelling across 400 kms of open ocean.

When they make it back to the reef, they’re only a few millimetres long and they have only a few days to make it there so they must be using ocean currents to assist their migration.

The researchers found that most of the fish travelled from North to South, while very few travelled in the opposite direction.

This direction corresponds to the dominant ocean currents in the region, which are driven by the
winter monsoon.

The study is published in the journal PLOS ONE.

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