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Not only will the invaders benefit from climate change, they will make it worse. But if their arrival is caught early enough, they can be kept at bay

At the end of a slippery dock in Tofino on Vancouver Island on a cold day in February, a crew from the Coastal Restoration Society, a non-profit dedicated to restoring and maintaining coastal health in B.C., is preparing for a fight.

The crew plows through the chilly wind, waves and rain to arrive in a shallow bay in Clayoquot Sound in the traditional territory of the Ahousaht First Nation, who are working with the Coastal Restoration Society to manage the crabs. The bay is fed by a salmon spawning river, perfect habitat for the invaders known as European green crabs.

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On the traditional territory of the Ahousaht First Nation, a salmon spawning river flows down into a muddy bay with eelgrass – perfect territory for the invasive European green crab.

From the stern of the Coastal Restoration Society's research vessel, trapping technicians haul traps from the depths of Clayoquot Sound.

One of the world’s most destructive invasive species is gaining new ground – or rather, water – in Canada. Carcinus maenas out-compete many local crab species, devouring clams, oysters and mussels, and sometimes even other crabs and juvenile fish. They destroy seagrass, which is an important habitat for juvenile salmon, herring, rockfish and many other marine animals. Seagrass is also an important carbon sink, 35 times more efficient at storing carbon than rainforests.

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The carapace of a European green crab is measured as part of the long-term monitoring program.

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European green crabs can lay 185,000 eggs at a time, which drift in ocean currents, growing the territory and population of the invasive species.

On Clayoquot Sound, the team starts pulling up traps. Coastal Restoration Society technician James George explains how they rotate their trapping between four different spots, staying in each spot a week to clear out as many crabs as they can. “We will slay today because we haven’t trapped here in a month,” he says.

European green crabs first arrived on North America’s east coast in the 1800s, likely in the ballast water of ships from Europe and North Africa. In the 1980s, they hitched a ride on vessels travelling through the Panama Canal and entered California’s waters. They reached B.C. in 1989. Almost everywhere our ships have gone, so too have the crabs. They are now established in Australia, South Africa, South America and on both coasts of North America.

The crabs are resilient and can tolerate a wide range of temperatures and salinities, but the young ones have a tougher time surviving in the cold temperatures of northern B.C. and Alaska. But as climate change warms those waters, it’s easier for the pests to spread northward.

The crabs begin life as tiny larvae, drifting in ocean currents, expanding their territory little by little to wherever is suitable, like the seemingly endless shallow inlets and estuaries of Vancouver Island. But they aren’t everywhere, yet. So far, the Salish Sea between Vancouver Island and the mainland is green-crab-free and a scare on Haida Gwaii was quickly and successfully dealt with. However, given how remote and complex these ecosystems are, more outbreaks are highly likely.

After the traps are retrieved, crabs are dumped into a bin for counting.
A mass of invasive European green crabs caught in Clayoquot Sound.
Joe Elley counts how many green crabs were caught in the trap.

Still, if their arrival is caught early enough, they can be kept at bay.

“You can really see the difference. We will catch fewer crabs by end of the week and the eelgrass has started to come back in places we trap,” says George.

Climate Innovators and Adaptors

This is one in a series of stories on climate change related to topics of biodiversity, urban adaptation, the green economy and exploration, with the support of Rolex. Read more about the Climate Innovators and Adaptors program.

The question of what to do with the crabs once they are caught is a prickly one. They are edible, if low-yield, but Health Canada hasn’t approved them for human consumption. Some fear that creating a profitable market for them will lead to intentional spread. For the moment, the Coastal Restoration Society flash-freezes them in a massive, industrial freezer. The crabs are subsequently turned into fertilizer that can be used by the Ahousaht – at their behest – or sent to landfill.

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Once the crabs are caught they are transported to a huge industrial freezer. Freezing the crabs is seen as the most humane way to kill them.

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Alex King, Regional Program Lead with the Coastal Restoration Society, navigates the crab-infested waters of Clayoquot Sound.

When I ask our captain, Alex King, a scientist and the Regional Project Manager with the Coastal Restoration Society, if she’s heard of the New Hampshire whiskey being made from the crabs, she laughs. “Yeah, everyone I know has asked me about that. It’s great for raising awareness about the issue and I think there is a lot of potential for more of that sort of thing, but it’s so small scale. We need to think bigger.”

The Coastal Restoration Society has become an efficient expert at catching the crabs with virtually no bycatch of unwanted species, but it is not equipped to turn the crabs into fertilizer, feed, bait, whiskey, bio-plastic bags or any of the other suggested uses for hundreds of thousands of crabs they catch. But there is an opportunity there for someone who can.

For now, we are stuck having to manage these crabs long term. “At least it’s permanent jobs,” shouts Joe Elley, a technician with the Coastal Restoration Society, over the roar of the engines as we glide back to Tofino.

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Off the shores of Tofino, in Clayoquot Sound, the Coastal Restoration Society continues the battle against the invasive European green crab.

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