Fish carried in from Japan tsunami find homes in aquarium exhibits

Banded knifejaw on exhibit.jpg

NEWPORT, Ore. - When several yellowtail jacks and a knifejaw were discovered in the hold of a derelict boat hull, scientists began scratching their heads, wondering what to do with the fish species that didn't belong in the eastern waters of the Pacific Ocean.

Now, the small school will call aquarium exhibits home.

The boat carrying the fish was spotted by fishers southwest of Newport in April 2015. Scientists say the yellowtail jacks and the one knifejaw originate from the western side of the Pacific Ocean. Genetic testing on the found fish later confirmed that they were indeed from waters near Asia.

RELATED | Fish native to Japan found in Oregon crab pot: Is it tsunami-related?

Jim Burke of the Aquarium and John Chapman, an aquatic invasive species specialist at the Hatfield Marine Science Center, examined the ship before it touched the Oregon coast to determine what species it could introduce to the area.

"Unlike oil spills or chemical leaks that gradually decline over years, decades or millennia, introduced species increase from a tiny initial numbers to massive populations that never go away," Chapman said.

When they discovered the fish, authorities towed the vessel into Yaquina Bay and allowed the aquarium to care for the fish. According to Chapman, this was safer than risking the boat crashing on a nearby shore and letting the fish get away.

Early on, some scientists suspected the boat drifted across the Pacific after the Thoku tsunami that inundated Japan in 2011. However, the origins of the boat were uncertain until Gayle Hansen, an algal taxonomist at the Hatfield Marine Science Center, devised a method to discover where the hull came from.

"My collaborator in Japan (Takeaki Hanyuda of Kobe University) completed a survey of the haplotypes of Ulva australis/pertusa species in Japan several years earlier. He was able to use this data plus his sequences from the Seal Rock Debris boat alga that we sent him to determine that the alga and boat were from the Iwate Prefecture of the Thoku coast of Japan where the tsunami took place," Hansen said.

Once the boat was pulled ashore and the threat of the exotic species was contained, the aquarium's staff began caring for the 21 fish.

Staff says six jacks succumbed to infections before treatment could eliminate the gill flukes that ailed them. The rest of the fix were healthy by early summer, but weren't ready for exhibit. Scientist say the limited diet inside the hull and the cold water of the Pacific may have stunted the fish's growth.

"They could not open their jaws wide relative to their size, so I had to prepare tiny, bite-sized food for them," said Evonne Mochon-Collura, assistant curator of fishes and invertebrates at the aquarium.

Once Aquarium staff refined a protocol tailored to the fishes' unusual life experience, the fish started to feed aggressively and were soon ready to transition to exhibit.

The yellowtail jacks can now be spotted in the Open Sea exhibit in Passages of the Deep, better known as the shark tunnel, where they appear to be thriving among a diverse population of pelagic fish species.

The banded knifejaw is settling into the California Kelp Forest exhibit in the Aquarium's Coastal Waters gallery, where it was joined by a member of its own species that was pulled up in a crab pot near Port Orford in February 2015.

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