Invasive European green crabs continue their advance

European green crabs are on the move in Southeast Alaska, so keep your eyes out for this invasive species and its distinctive ‘5-3-5’ carapace.

According to the Alaska Department of Fish and Game (ADF&G), European green crabs in Alaska are growing in numbers and extending their range northward. They are asking residents of the southern Panhandle to keep careful watch for the crabs, which have advanced around 90 miles since first being detected in Alaska four years ago. Unlike native Alaskan crabs, the crabs have five spines on either side of their eyes and three bumps between the eyes.

“The advance of these crabs is rapid, but it’s by no means inevitable,” said Tammy Davis, coordinator of the ADF&G Invasive Species Program. “We need Alaskans to look out for ‘5-3-5’ to help us understand the spread of these harmful invasives.”

European green crabs first appeared in Alaska on Annette Island in July 2022. Since then, the number of crabs trapped in Alaska has increased more than fiftyfold. Crabs were found on Gravina and Prince of Wales islands in 2024, and in Ketchikan in spring 2025. Last fall, a carapace was found as far north as Etolin Island, just south of Wrangell. The population has been expanding dramatically around Ketchikan, where either carapaces or live crabs have been found on 10 beaches in the last year.

Green crabs are highly adaptable and can survive in many different environments, from rocky shores to mud flats to tidal marshes. The invasive crabs can damage eelgrass beds, which provide critical habitat for juvenile salmon, Pacific cod, and other fish and shellfish. They also eat small clams, which are a vital subsistence food, and outcompete native species like Dungeness crab.

European green crabs are classified in Alaska regulations as a banned invasive species, which means possessing or transporting them without a permit is prohibited. ADF&G is instead asking individuals who spot any to note the number of crabs and their location, take photos of the crab(s) from different angles along with a standard-sized item for scale, like a pencil, key, or credit card, and report the European green crab find via phone or email.

“Fish and Game has a number of tools at its disposal for reducing populations of these invaders,” noted Sunny Rice, a Marine Advisory Program agent for Alaska Sea Grant who is helping track the crabs’ spread. “But first we need thorough intel on where they’re spreading, which is where Alaskans can help.”

Individuals interested in volunteering to search for European green crabs can call 1-877-INVASIV to learn more. Alaska Sea Grant also offers free stickers to help identify the crabs.