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Brightly Colored, 100-Pound Moonfish Washes Up on Oregon Beach

Scientists say this open-ocean species, also known as an opah, typically inhabits warmer waters than those of the Pacific Northwest

An opah or moonfish that washed up on Sunset Beach in northern Oregon on July 14. (Tiffany Boothe / Seaside Aquarium)
smithsonianmag.com

Last week, a 100-pound fish shaped like a manhole cover and festooned in silver and coral-orange scales washed up on a beach in Seaside, Oregon. The exotic-looking denizen of the deep is called an opah or moonfish and is seldom observed so far north, according to the local Seaside Aquarium, which was alerted to the washed-up sea creature by beachgoers.

These striking, open-ocean fish can weigh more than 600 pounds and grow to more than six feet in length after spending many years feasting on their favorite foods like krill and squid, reports Oliver Milman for the Guardian.

Opah typically inhabit warmer waters, such as those off the coasts of California and Hawaii, but it’s not completely unheard of to encounter one in Oregon waters. In 2009, a fisherman caught a 97-pound opah while plying the mouth of the Columbia River just north of Seaside, reports Jamie Hale of the Oregonian.

Heidi Dewar, a fisheries biologist with National Oceanic and Atmospheric Administration (NOAA), tells Paulina Firozi of the Washington Post that she normally wouldn’t expect to find a 100-pound opah off the Oregon coast.

In the weeks leading up to the opah stranding, the Pacific Northwest was broiled by an intense heatwave that killed an estimated one billion marine organisms—with clams and mussels being cooked alive inside their shells. Scientists say the extreme heat would have been “virtually impossible” without climate change, according to the Guardian.

There isn’t any data explicitly linking the unusual fish stranding to the heatwave or climate change, but, speaking with the Post, Dewar suggests rising ocean temperatures could have played a role in the unique sighting.

“We are seeing some marine organisms moving northward as ocean temperatures increase,” Dewar tells the Post. However, she also noted the fish’s normal range is in “close proximity to Oregon, so it’s not super surprising.”

Despite their conspicuous appearance, relatively little is known about the opah’s basic biology, such as their maximum age, according to the Post.

The Seaside Aquarium retrieved the opah’s virtually undamaged body and placed it in a freezer for preservation. With the help of the nearby Columbia River Maritime Museum, the aquarium intends to give a school group the opportunity to dissect the fish’s remains during the coming academic year.

“Not a lot is known about these beautiful fish, so anything we can learn will be beneficial,” Tiffany Boothe, assistant manager at the aquarium, tells the Post. “This will also give students the unique experience of dissecting a really cool fish that they may never come across again in their day-to-day lives.”

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