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A highly invasive crab species capable of scaling structures over 13 feet tall has been reported in the Pacific Northwest for the first time, according to wildlife officials. This significant discovery was made when a commercial fisherman caught a Chinese mitten crab in the Lower Columbia River, just south of the Washington state border, as stated by the Oregon Department of Fish and Wildlife, which also distributed a photo of the crab.
The department noted, “Chinese mitten crabs have not been confirmed in the Pacific Northwest until now,” in a news release.
Officials indicated that this invasive species has caused significant damage to ecosystems and infrastructure, particularly in San Francisco Bay three decades ago. “While this is a rare occurrence in Oregon, mitten crabs led to extensive ecological destruction and infrastructure issues in and around San Francisco Bay during the peak of their population in the late 1990s,” as reported by the department.
The crab in question was identified as a large male, which may have found its way into the river illegally, either through human intervention or via ballast water from ships.
Understanding Chinese Mitten Crabs
Chinese mitten crabs are an invasive species hailing from East Asia. The Smithsonian Institution notes that these crabs first became invasive in the San Francisco Bay during the 1980s, later spreading to the East Coast, with recent sightings reported in New York.
Distinguished by their hairy, mitten-like claws, these crabs come in shades ranging from brownish-orange to greenish-brown. They possess unique features not found in native crab species, including four spines on each side and a distinct notch between their eyes.
According to the U.S. Bureau of Reclamation, these crabs can scale concrete structures up to 13 feet tall. “Mitten crabs can also navigate through lock systems and potentially climb fish ladders, or even leave the water to traverse barriers when the terrain allows,” the bureau adds.
The species has a reputation for stealing fishing bait, damaging fishing gear, and obstructing power plant cooling systems. Moreover, they can exacerbate flooding risks by burrowing into banks, destabilizing the terrain.
Chinese mitten crabs primarily inhabit freshwater but require saltwater for reproduction. The Oregon Department of Fish and Wildlife explains, “Newly hatched larvae thrive in open saltwater in bays and estuaries, while fully molted juveniles can be found in brackish and freshwater areas just a few miles upstream from saltwater.”
Looking Ahead
Wildlife biologists in Oregon are collaborating with the Washington Department of Fish and Wildlife and NOAA to investigate the potential presence of additional mitten crabs in the region. Officials plan to establish trap lines and collect water samples in search of “environmental genetic markers specific to the mitten crab.”
In the interim, officials are encouraging the public to remain vigilant for sightings of this invasive species and to report any occurrences to the Oregon Department of Fish and Wildlife or the Oregon Invasive Species Council.
“Correct identification of this species is crucial, and any sightings should be reported to your local ODFW office along with the location where it was found,” the Oregon Department of Fish and Wildlife emphasized.
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