It's European Green Crab Day! The green crab is considered one of the most invasive species in the ocean— it has few predators, aggressively hunts prey, destroys seagrass, and outcompetes local species like the Dungeness crab.
Green crabs first hitched a ride over to North America in the 1800s, in the ballast water of ships coming from Europe. They spread down the East Coast, eventually reaching the West Coast by the early 1900s. From there, they rode ocean currents further north up the Pacific Coast. The currents carried crab larvae enormous distances, where they settled and grew into adult crabs.
In 2022, European green crabs were spotted in southeast Alaska for the first time. On July 19, 2022, the Metlakatla Indian Community discovered three crab shells during an Annette Islands Reserve survey south of Ketchikan. By August 17, they had found 56 live green crabs, 13 crab shells, and six dead crabs from Tamgas Harbor and two from Smugglers Cove.
In July 2025, European green crabs were also found in Refuge Cove State Recreation Site, north of Ketchikan. Two small carcasses were found during a University of Alaska Southeast survey.
If the crabs keep marching north, they could have serious effects on Alaska’s commercial and subsistence fisheries.
Green crabs are highly adaptable and can survive in many different environments, from rocky shores to muddy estuaries, protected bays, and salt marshes. They are voracious eaters, guzzling down clams, mussels, Dungeness crab, and small fish, as well as juvenile king crabs and juvenile salmon. They also rip up eel grass, which forms an important habitat for Dungeness crabs and juvenile salmon.
While eradication may be impossible, efforts are underway to protect Dungeness and salmon habitat from green crabs. The best way to help is to keep an eye out for the invasive species. Green crabs can be green, but they can also be brown, orange, or yellowish. The best way to identify them is to look at the shell; they have three small bumps between the eyes, and five jagged spines on either side of their eyes. ADFG has a guide to identifying green crabs.
If you spot a green crab, leave it alone, but make sure to take photos and report it to the Invasive Species Hotline: (877) 468-2748. Learn more from NOAA Fisheries below!
