Coastal Restoration Society lead biologist Crysta Stubbs and environmental consultant Spencer Binda helped trap, document and destroy European green crabs at a newly discovered site infestation on the West Coast of Vancouver Island this month. (Photo - Capt. Josh Temple)

Invasive green crabs spark massive trapping project near Tofino

Coastal Restoration Society monitoring populations in Clayoquot Sound and Sooke Basin

When it comes to the West Coast’s crustacean population, green means got to go.

The Coastal Restoration Society is putting together a massive trapping project aimed at drastically reducing European green crabs in B.C. waters.

“I would say that European green crabs pose the most significant risk to our marine resource that I’ve seen in my lifetime,” the society’s co-founder and lifelong Tofitian fisher Capt. Josh Temple told the Westerly News.

Temple said the project involves commercial prawn traps that have been modified to specifically target European green crabs and reduce snagging other species by mistake. He added that all bycatch is released alive and unharmed while green crabs are collected, sampled and responsibly destroyed, though the society is working with DFO to explore potential harvesting.

“We’re working to ensure that we’re not just wasting a useable resource. They’re edible, they’re quite delicious actually and if this is an opportunity for a small scale commercial fishery that our First Nations can run, then that’s definitely something we are very interested in developing in partnership with DFO,” he said.

While not native to B.C., European green crabs, unaffectionately known as EGC, are considered an established species on the west coast of Vancouver Island, according to DFO scientist Thomas Therriault.

They arrived in North America in the late 1980’s, hitching rides on packing materials being shipped between Europe and San Francisco where they then spread throughout the Pacific coast due to larval drift, landing in Ucluelet and Barkley Sound in the late 1990’s, Therriault told the Westerly, adding that DFO has been monitoring the species in Barkley Sound since 2004.

Therriault said EGC can quickly destroy eelgrass beds, which serve as vital habitats for a variety of local species like juvenile salmon and herring.

“Our concern from a science perspective is that European green crab can have effects on habitat and on important species and, if the populations increase, we would expect the impacts to increase. Therefore, any control or mitigation at the local scale to preserve ecosystems would be positive,” he said.

“As European green crab become established and as populations grow, you would expect the impacts to grow with them. In the invasion process, typically you go through this period of population growth as the species comes into the system…They’re a predator species. They are consuming mussels, clams, cockles, small crabs and other small crustaceans. There is a predation pressure exerted on our native species.”

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Therriault said it is tough to confirm whether EGC numbers are rising substancially on the West Coast, explaining that DFO’s monitoring sites are set in fixed locations and can’t track whether populations are moving to other areas.

“We have information for specific beaches that we track, but we don’t necessarily have the resources to conduct trapping at every single beach in Clayoquot or Barkley…There’s a number of potential sites that would have green crab, we’re limited in terms of the amount of time and resources we have to survey areas,” he said. “From the work that we’ve done, we know that green crab can pose risks to Canadian ecosystems and the species that live in them. Whether it’s more problematic now than it was 20 years ago, I think, is difficult to say.”

He added though that EGC can wreak havoc on marine habitats regardless of whether their populations are booming.

“Some invaders do go through a boom and bust cycle, others never seem to boom and others never seem to bust…That’s where we’re sort of struggling. We know that they’ve been here for a while, we know that they’re likely having impacts. The difficulty is we don’t have pre-invasion baselines to compare to,” he said. “Even when populations are lower in certain years, they’re still consuming native species and they can still degrade eelgrass habitats. It’s not like any of the sites go to zero. The only way that an invader’s not going to have an impact is if it’s not present.”

Jennifer Yakimishyn, a marine ecologist with the Pacific Rim National Park Reserve, told the Westerly that the Park Reserve has been monitoring European green crabs since 2014 through traps set up at eelgrass-rich sites.

“The information we gather through this monitoring work and related Parks Canada-led and external studies will inform how we continue to protect nearshore marine environments, including eel grass meadows, moving forward,” she said.

She said the Park Reserve has documented an increase in EGC around Grice Bay, but has not seen significant population growth in the Broken Group Islands since monitoring began.

“In 2016, Parks Canada led a short-term European green crab removal effort study at three sites in the Broken Group Islands. Unfortunately, this removal effort showed no overall impact on European green crab numbers,” she said.

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Both the Park Reserve and DFO have put their monitoring efforts on hold due to the coronavirus pandemic.

Temple said he began noticing an increase in EGC around 2014 while fishing in Clayoquot Sound and he also started spotting huge numbers of green crab carcasses washed up on local shorelines during the ambitious Clayoquot Cleanup project he founded in 2017.

“Their populations have been expanding rigorously here in Clayoquot Sound over the years but I think the environmental conditions, particularly in the last four years, have created somewhat of a perfect storm for EGC proliferation and now we’re dealing with a massive outbreak of European green crabs,” he said. “What’s scary is that we have discovered here in Clayoquot Sound site infestations in Lemmens Inlet and at Browning Pass where DFO has never identified green crabs being present before.”

He added that EGC have been able to “survive and thrive” in Clayoquot Sound’s eelgrass rich waters and that anecdotal evidence has suggested an alarming evolutionary shift.

“One of the things we’ve discovered here in Clayoquot Sound, and it’s the first time that this has been documented, is that EGCs are actually seeking out and preying upon live, juvenile salmon,” he said. “This is very disturbing because that’s something that hasn’t been documented scientifically before…Obviously more research is needed here, but that could point to an evolution in their predatory behaviour that, now that they are establishing themselves in Pacific salmon habitat, they could be adapting and adopting their predatory behavioural patterns to specifically prey on juvenile salmon. So, that’s very, very, very troubling.”

Temple noted that DFO lists EGC as “one of the ten most unwanted species in the world,” and said the Coastal Restoration Society plans to launch preliminary trapping pilot projects in both Clayoquot Sound and Sooke Basin within the next several months before trying to tackle the entire Pacific region.

Therriault cautioned that removing the species from local waters would be extremely difficult due to larval drift from nearby established populations around Washington, Oregon and California.

“The issue is that there’s always going to be larvae seeding the area. In some years, when conditions are good, you’ll have more of them surviving and in other years, when conditions are harsh, you’ll have fewer,” he said. “You’re not ever cutting off that larval supply unless you’re trapping out all of those other populations as well.”

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Temple said widespread monitoring and population control of EGC would only be possible if adequate support is received from the federal government.

“I firmly believe DFO and the team that they have working on EGC are doing a remarkable job, the problem is that Ottawa is not giving them enough resources and funding to really tackle the problem on the scope and scale it needs,” he said. “We are very supportive of the work that DFO is doing. Where we need more help from is from Ottawa and the highest levels of the federal government. Right now, we don’t have the proper resources or funding to give this problem the attention it deserves, so we really need some help from the Prime Minister’s office and from the fisheries minister to make sure we’re seeing the resources and the funding we actually need.”

Anybody interested in supporting the society’s efforts can reach out through its website at www.coastrestore.com or email info@coastrestore.com.

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andrew.bailey@westerlynews.ca

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