'Green crab numbers have reached a critical point': Invader spells trouble for Coos Bay
COOS BAY, Ore. – The number of invasive green crabs in the Coos Bay region continues to grow - and are likely to impact Dungeness crabs and coastal habitat, according to a new report by researchers at South Slough National Estuarine Research Reserve.
Dungeness crab is Oregon's most valuable commercial fishery.
The report is part of an ongoing study by scientists from the South Slough Reserve and Oregon State University.
Between June and September of this year, the researchers trapped and sampled crab populations daily at 13 sites around Coos Bay.
On average, 73.3% of crab species trapped each day were green crabs.
“Green crab numbers have reached a critical point where we can begin to expect negative impacts on surrounding coastal and estuarine habitat and other organisms,” said Dr. Shon Schooler, lead scientist and research coordinator at South Slough Reserve. “This is turn may impact our local fisheries.”
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According to the State of Oregon:
Green crabs dig up and eat eelgrass meadows, destroying the seagrass many organisms rely on for food and shelter. They also displace juvenile Dungeness crabs from habitat where they shelter and feed, leaving Dungeness vulnerable to predators. Additionally, green crabs prey on clams, oysters, and mussels, reducing populations of these bivalves.
Dr. Sylvia Yamada, an assistant professor at Oregon State University, said the rise in green crabs measured in Coos Bay reflects what is happening in other estuaries along the Oregon coast.
“All estuaries follow similar trends,” Yamada said. “In the past, green crab larvae were carried in warm ocean currents to Oregon from established populations in California. Now that green crabs are abundant in Oregon, Washington and British Columbia, there is evidence some larvae are coming from the north, while others are reproducing locally. This doesn’t bode well for the future unless we get a series of years when the water is colder.”
