European green crabs, a particularly invasive species known for aggressively displacing native species and damaging important vegetation, have been found on Etolin Island just southwest of Wrangell.

A monitoring effort that spans much of Southeast is working to identify and possibly mitigate their continued spread northward.

The crabs were first found in Metlakatla in the summer of 2022. Since then, they’ve been found increasingly farther north, with Etolin Island the northernmost confirmed sighting of the crabs so far.

Tammy Davis, the invasive species coordinator for the Alaska Department of Fish and Game, said on Nov. 3 that the crabs are able to establish themselves in varied environments, with impacts to local ecosystems.

The hearty eaters feed on indigenous species including salmon fry and juvenile Dungeness crabs, and damage important beds of vegetation — like eelgrass —that are essential fish habitat.

“Eelgrass is so important,” Davis said. “It’s a keystone species for intertidal foodwebs and ecosystems generally, but it’s really important for the species that are valuable to Alaskans.”

It was a report from a person who was out recreating on Etolin Island, Davis said, that alerted officials on Oct. 5 of a potential invasive crab sighting on Oct. 2. Davis said the man reported finding the crab at “a bay north of Cooney Cove on Etolin Island.”

Cooney Cove is about 30 miles southwest of downtown Wrangell, about 10 miles northeast of Coffman Cove.

“While it’s alarming, it’s not necessarily surprising that the distribution of green crab has expanded since 2024,” Davis said. “I’m concerned about how far north the crab has been able to expand.”

The expansion of the population has been facilitated by recent conditions including an El Niño — described by the National Oceanic and Atmospheric Administration as a time when cold, nutrient-rich waters in the Pacific Ocean fail to rise and surface temperatures remain warmer than usual.

Davis said European green crabs have been a concern of the department’s for decades, as modeling from the early 2000s suggested that warming oceans could allow the crabs to expand all the way through the Aleutian chain.

She said she’s seeking people in Wrangell to be a part of a network of community members across Southeast who are “actively involved in early detection surveys.”

That effort, spearheaded by the nonprofit Southeast Alaska Tribal Ocean Research, has walked beaches, placed traps and raised awareness of the crabs to generate reports of potential sightings of crabs or their carapaces.

There are two groups in Petersburg who are trapping crabs to monitor for European green crab. “We don’t have anybody in Wrangell.”

European green crab, despite their name, aren’t always green, Davis said. The “simple key” to identifying them is by counting the spines on their carapace. Green crabs have five spines on either side of their eyes, and another three between the eyes.

The green crabs are small, only around four inches across their bodies at adult size. If a possibly invasive crab or any other organism that doesn’t seem to belong is sighted, the department has an invasive species hotline and an online reporting tool to collect reports.

Davis said she’d be happier to receive reports of native crabs suspected of being invasive than no reports. Like with the crab found on Etolin Island, department staff can investigate to verify and implement mitigations.

The department also asks people not to attempt to kill the crabs — the department wants to verify their identities.

Because the crabs are spread on ocean currents, “we don’t believe that eradication is possible,” she said. “Instead, in communities where the crabs have been established, work will be done to suppress the population in valuable areas. In Metlakatla, for example, targeted trapping is underway in areas of the Tongass National Forest and the Annette Islands Reserve.”

Invasive species can be reported to the Department of Fish and Game via an online portal at adfg.alaska.gov or by calling 1-877-INVASIV.

More information about the Alaska Invasive Species Partnership can be found at alaskainvasives.org.