Five years after Japanese tsunami, concern over invasives still exists

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Sam Chan tells visitors to the washed-up Japanese dock about invasive species that may have hitched a ride

Oregon State University Natural Resources Leadership Academy (NRLA) Agate Beach, tsunami debris field trip, June 21, 2012.

Five years after a massive earthquake struck Japan and triggered a tsunami that is still washing debris onto the West Coast of the United States, scientists are unsure whether any of the 200-plus non-native species that hitchhiked over on that debris have gained a foothold in Northwest waters.

Four separate findings of barred knifejaws (Oplegnathus fasciatus) – a fish native to Japan – have been reported over the past three years, and Mediterranean blue mussels have been ubiquitous on tsunami debris. Yet no populations of non-native species that arrived with the tsunami debris are known to have established reproductive populations.

“Maybe we dodged the bullet, although it is still too early to tell,” said John Chapman, an Oregon State University invasive species expert who has investigated tsunami debris along the Pacific coastline. “It is possible that we have not yet discovered these reproductive populations, or that some species from Japan may be cross-breeding with our own species.”

Scientists have not had adequate resources to look extensively up and down the Pacific coast for evidence of establishment by non-native species – especially along long stretches of rugged shoreline.

The magnitude-9 earthquake that struck Japan on March 11, 2011, was the largest in that country’s history and generated a tsunami that had waves estimated as high as 133 feet. The power of these two events, combined with the growth of human settlement over the past two to three centuries, created a new paradigm, said Samuel Chan, Oregon Sea Grant’s expert in aquatic ecosystem health and invasive species.

“A tsunami 300 years ago, or even just 60 years ago, would not have created as much marine debris that became a vehicle for moving species across the Pacific Ocean that could become invasive,” Chan said. “What makes these major tsunami-driven events different in modern times is the substantial human industrial infrastructure that we have built along the Pacific coast.”

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