Tsunami fish wash up in US

Nearly 300 species of fish, mussels and other sea creatures hitchhiked across the Pacific Ocean on debris from the 2011 Japanese tsunami, washing ashore alive in the US.

It is the biggest and longest marine migration ever documented, researchers and experts said.

Scientists and colleagues combed the beaches of Washington State, Oregon, California, British Columbia, Alaska and Hawaii and tracked the species to their Japanese origins. Their arrival could be a problem if the creatures take root, pushing out native species, the study authors said in the journal Science.

“It’s a bit of what we call ecological roulette,” lead author James Carlton, a marine sciences professor at Williams College, in Massachusetts, said.

It will be years before scientists know if the 289 Japanese species thrive in their new home and crowd out natives.

The researchers roughly estimated that a million creatures travelled 7725km across the Pacific Ocean to reach the west coast of the US, including hundreds of thousands of mussels.

Invasive species is a major problem worldwide with plants and animals thriving in areas where they do not naturally live.

A magnitude 9 earthquake off the coast of Japan triggered a tsunami on March 11, 2011, that swept boats, docks, buoys and other man-made materials into the Pacific.

The debris drifted east with an armada of living creatures, some that gave birth to new generations while at sea.

“The diversity was somewhat jaw-dropping,” Professor Carlton said. “Molluscs, sea anemones, corals, crabs, just a wide variety of species, really a crosssection of Japanese fauna.”

Last year, a small boat from Japan reached Oregon with 20 good-sized fish inside, a kind of yellowtail jack native to the western Pacific, Professor Carlton said.

Earlier, an entire fishing ship, the Sai sho-Maru, arrived intact with five of the same 15cm fish swimming around inside.

The researchers note another huge factor in this flotilla: plastics.

Decades ago, most of the debris would have been wood and that would have degraded over the long ocean trip, but now most of the debris is made of plastic and that survives.

More than 10 million tonnes of plastic waste enter the oceans each year.