Earlier this year, two crab boats pulling up their pots off the Central Oregon coast found something out of the ordinary. In each instance, it was a full-grown Dungeness crab, but one that lacked almost any trace of coloration in its shell.
“I’ve seen an all-white Dungeness once before, in 2013, but I never thought I’d see another,” said Roman Smolcic, a fisherman working aboard the F/V Norska, one of the boats that found the white crabs. He and his crewmates were pulling pots near Cascade Head in January when they happened upon the ghostly Dungeness. “The other guys on the crew had never seen a crab like that. We took a vote on it and decided that we should donate the crab to the Aquarium, so that other people could have a chance to see this unusual animal alive.”
Smolcic’s crab and the other individual (both captured in early 2017) were spared from consumption and brought to the Aquarium, where they’re now on exhibit in the Sandy Shores Gallery. According to Scott Groth, a shellfish biologist with Oregon’s Department of Fish and Wildlife (ODFW), these pale crabs are quite rare. The estimated occurrence is thought to be as low as one in a million—and to have not one but two adult individuals come to the Aquarium at nearly the same time adds another element of improbability.
“In Oregon we harvest between 15-20 million pounds of Dungeness a year,” said Groth. “Each adult crab averages about two pounds. That’s something like 8 million crabs annually. We receive reports of these anomalous individuals maybe two or three times a year, so the odds of finding them are quite low.”
Dungeness crabs are opportunistic animals, grazing on detritus as well as feeding on many species of fishes and invertebrates. The usually brownish-purple coloration of these crabs likely helps to camouflage them in the murky depths. How an all-white individual managed to escape detection by predators for long enough to mature is a mystery. “Juvenile Dungeness crabs are prey items to a wide variety of animals,” said Mitch Vance, Shellfish Project Leader at ODFW. “If an all-white juvenile crab is crawling around on the bottom, almost glowing against the dark substrate, it’s more likely to be picked off by predators.”
Once crabs pass the tricky juvenile stage and mature into adults, the better their chances at survival, Vance said. Fewer animals can deal with a full-grown Dungeness. Somehow, these two white crabs successfully avoided predation as juveniles—only to fall prey to the allure of crab pots as adults. While an all-white crab might seem strange, it turns out that such aberrations are known to occur on something of a spectrum. ODFW reports that crabs are brought to their attention with partial lack of pigment, hyperpigmentation, or pigmentation in odd patches or patterns.
Dungeness crab is an iconic species of the Pacific Northwest, prized for its delicious and commercially valuable meat. At the Aquarium, we regularly feature Dungeness crabs in our exhibits, and even devote an entire day event to them. It’s an animal that can be found right outside our doors, in the brackish waters of Yaquina Bay. Dungeness crabs enter estuaries to feed and seek shelter, and their larvae find refuge in the expansive eelgrass beds. Dungeness crabs typically live to about 10 years, reaching adult size at 4-5 years old. The white crabs in our Sandy Shores Gallery measure more than eight inches across the carapace—they’re definitely adults, but their age is unknown. Catch a glimpse of these “Great White” crabs during your next visit!
The Oregon Coast Aquarium creates unique and engaging experiences that connect you to the Oregon Coast and inspire ocean conservation. An accredited Association of Zoos & Aquariums institution, this 501(c)3 non-profit organization is ranked as one of the top 10 aquariums in the U.S. Visit us at 2820 S.E. Ferry Slip Rd., Newport, OR. www.aquarium.org, 541-867-3474. Follow us on Facebook.com/OregonCoastAquarium, or Twitter.com/OrCoastAquarium for the latest updates.
Information and photos provided by Oregon Coast Aquarium