The invasive European green crab continues to keep a presence on the North Olympic Peninsula.
For the third year resource managers at the Washington National Wildlife Refuge in Dungeness are capturing the crab, known for its five spines on the side of each eye, that competes with native species such as Dungeness crab and eats local clams and oysters.
Lorenz Sollmann, deputy project leader at the refuge, said staff and volunteers have trapped 56 green crab this season so far — down from 69 in 2018 and 96 in 2017, when the crabs were first discovered on the Dungeness Spit.
That’s 221 green crabs over three years. None, however, had been captured between 2001, when trapping began, and 2016.
Sollmann said the captures wouldn’t be possible without 30 dedicated volunteers.
“Their time commitment in support of this project is seven times more than the refuge staff has been able to provide with two refuge staff dedicated to this project,” Sollmann said.
“These staff members are also working on the five other refuges this office manages, so the volunteers make all the difference in the world.”
This season, volunteers and staff set 2,118 traps. The 42 males and 14 females captured have an average size of 65 millimeters.
Sollmann said captures slowed since mid-June, with most days bringing just one or two crabs.
“We have continued to periodically trap in areas of possibly suitable habitat but have found no new productive spots,” he said.
“However, this has taken much lower priority than in years past. We also have been leaving out one burrow tube that (Washington Department of Fish & Wildlife) gave us, which the shore crabs like but no (green crab) this year.”
Trapping in Dungeness goes into October.
West End invasion
On the West End, Makah tribal staff continue to find the invasive crab by the trap load.
Adrianne Akmajian, marine ecologist with Makah Fisheries Management, said her staff and volunteers captured 988 green crabs so far.
Of that, 642 were in the Tsoo-Yess River, 342 in the Wa’atch River and four in the rocky inter-tidal area near Tsoo-Yess Beach.
Akmajian said so far 166 crabs were caught by hand.
“Hand catches are quite fun,” she said. “My staff will wade in the rivers or in the side channels or tide-pools, which often disturbs the crabs. We use a net or just our hands to grab them.”
Her staff even went snorkeling to catch some crab by hand on the Tsoo-Yess River, she said.
Akmajian’s 10-year-old stepdaughter also caught 46 green crab in her shrimp trap, too.
The smallest green crab they’ve found was 9 millimeters while the largest was 92 millimeters.
Akmajian said their totals are about three times as many males as females; no females with eggs have been caught.
Traps are set in Neah Bay, but no green crab have been discovered there yet.
Akmajian said the crabs found at Tsoo-Yess Beach “might signal that the crabs are moving out to other habitats.”
She said, “I think by the end of our official trapping season (late April-early October), we will have caught more crabs total than we did all last year.”
Last year, the Makah Tribe captured 1,030 green crabs.
They began trapping specifically for the invasive species in 2017 after a passer-by discovered a green crab near the Wa’atch River and reported it to Washington Sea Grant. This led to intense trapping efforts to catch 34 green crab.
For this year’s efforts, 10 volunteers have assisted staff from Sequim, Port Angeles, Forks and Neah Bay for more than 250 hours.
Marine ecologist Emily Grason, Crab Team program manager for Washington Sea Grant, reports Neah Bay and Dungeness remain the largest totals for European green crab captures across the Salish Sea.
Smaller numbers have been captured in various spots, including: two in Sequim Bay, four in Samish Bay (three in January, and one in early August) and five in Whatcom County (one in Squalicum Harbor, one in Drayton Harbor and three in Chuckanut Bay).
Grason said in an Aug. 14 blog post that the lower numbers are consistent with Canadian colleagues with early detection sites.
“We hope that these findings signal that green crab arrivals are infrequent, with a small number of larvae getting washed in irregularly,” Grason wrote.
“That situation would afford us the best chance to prevent or reduce the potential economic and ecological damage green crab could cause if they were to become established.”
On the North Olympic Peninsula, Crab Team continues to coordinate monitor sites with the Lower Elwha Tribe at the Pysht River, Dungeness Landing, Washington Harbor and Jimmycomelately Creek in Sequim Bay and Discovery Bay, and Kala Lagoon and Indian Island in the Port Townsend area.
Grason said in an interview that they emphasize the need to support the removal efforts in Dungeness and Neah Bay.
“The work both the Makah and (Wildlife Refuge) are doing at their respective sites is incredibly important and needs to continue in order to benefit the entire Salish Sea,” Grason said.
“In some ways they are the ‘front lines.’”
Grason said resource managers believe low capture totals at new sites represent an invasion is still early enough that they “have a much better shot at controlling their numbers than if we were pulling up hundreds at a time.”
“We know that trapping captures only some of the crabs at a given site, and that if we want to really reduce the population at a site we have to trap continuously over a long time,” she said.
“So you worry about the crabs that you’re not catching, which could be out there reproducing and increasing the spread of the invasion before you can remove them from the habitat. At the same time, you worry that more larval crabs could be getting washed in, undoing all your work removing crabs.”
However, Grason said evidence isn’t showing either of those.
“It means we might actually be reducing their rate of spread and population growth, and also that the Salish Sea might be somewhat protected from green crab larvae getting washed in on a regular basis,” she said.
“Hard work and luck: these are the two critical ingredients we need to effectively manage this global invader.”
How to help
With European green crab confused with other species of crab, Grason recommends locals learn the differences through resources, such as wsg.washington.edu/crabteam/greencrab/id.
If someone thinks they’ve found a green crab, take photos and email them to email@example.com, but leave the crab in place to avoid accidentally killing native crabs.
Volunteers for 2020 can email the same address to join a training workshop in March 2020.
Reach Matthew Nash at firstname.lastname@example.org.