Forest Service will help look for invasive crabs around Wrangell

A European green crab captured in Grays Harbor, Washington, during July 2024. (Washington Department of Fish and Wildlife photo)

By Larry Persily

Wrangell Sentinel

The U.S. Forest Service has stepped up to help look for invasive European green crabs at Anan Creek and elsewhere in the Wrangell area.

The Alaska Department of Fish and Game put out a call earlier this month, seeking volunteers to help monitor for the small but habitat-destroying crabs moving into the area.

Forest Service staff set up traps last week at Anan, where the agency maintains a summer crew for the bear-viewing season.

“We’re also trying to involve the Wrangell Cooperative Association to go to other shorelines around the district,” said Anna Tollfeldt, a natural resource specialist with the Wrangell Ranger District.

The WCA’s Tl’átḵ | Earth Branch wants to work with the Forest Service to monitor area shorelines, said Lexie Hayes, with the tribe’s subsistence and environmental program. She said it would be next month at the earliest before a shared operation could get underway.

Kayleigh McCarthy, a Forest Service Anan technician, will focus on looking for the crabs in that popular wildlife viewing area, Tollfeldt said. The agency runs crews through Anan, living aboard a floathouse for the summer, which will make it easier for workers to set and check crab pots and walk the beaches.

“We’re just trying to help with the monitoring effort,” Tollfeldt said. “The biggest thing is knowing how to identify them.”

“Despite their name, European green crabs are not always green — they can range from orange, yellow and red to brown or grey,” according to the U.S. National Marine Fisheries Service. “The most definitive way to identify them is by counting the five sharp spines behind each eye, and the three rounded bumps directly between the eyes.”

If the Forest Service finds a crab in its traps or on the shoreline, Tollfeldt said, the plan is to take photos “and get it to them as fast as we can,” sending the information to the Alaska Department of Fish and Game’s invasive species office.

The state agency provided half a dozen crab traps for the Forest Service Wrangell district.

The plan, Tollfeldt said, is to set the traps and check them 24 hours later, and share the traps between Anan and elsewhere in the district. “They want us to sample as many places as we can.”

The crabs, which were first discovered in Alaska in 2022 at Annette Island, have spread northward and were discovered last October at a bay north of Cooney Cove on Etolin Island, across Clarence Strait from Blashke Islands.

The Wrangell Ranger District will try to check the shorelines around Etolin, but that requires decent weather for a skiff ride. “Clarence Strait can be a gnarly body of water,” Tollfeldt said.

“The green crab is considered one of the most invasive species in the marine environment,” according to the federal fisheries service. “It has few predators, aggressively hunts and eats its prey, destroys seagrass and outcompetes local species for food and habitat.”

The description gets worse: “It has been documented that green crab devour juvenile king crab as well as juvenile salmon. They also destroy eelgrass habitat that larval fish use to hide from predators and outcompete Dungeness crabs for food and habitat.”

Southeast Alaska provides prime habitat for the invasive crabs, which arrived in North America in the 1800s, likely in the ballast water of merchant ships from Europe before coming to the West Coast the same way, the federal agency reports.

“Green crabs live on rocky shores, cobble beaches, sandflats and tidal marshes. They can often be found near eelgrass beds or other shoreline vegetation. … They can also survive upstream of river mouths in some estuarine environments.”

An early detection manual issued by a collection of state, federal, university and tribal partners provides advice on what to look for and where: “All crabs must molt to grow, and the molted exoskeletons (carapaces) are often deposited by the high tide onto the upper beach with seaweed and other beach wrack (organic materials) and debris.”

The manual notes that “searching for molts provides a method for volunteers to detect European green crabs in nearby waters.”

The state has guides and identification information for anyone interested in helping with the search effort.

For more information, or if a green crab is suspected, people can call the Invasive Species Hotline 1-877-468-2748 or email dfg.dsf.InvasiveSpecies@alaska.gov.

• This article originally appeared in the Wrangell Sentinel.