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This piece was first published in .

Imagine the worst house guests: demanding, confrontational, destructive. Uninvited and refusing to leave. Then their friends show up and suddenly the fridge is empty, the TV is broken and you’re sleeping on an air mattress on the balcony.

That’s just a taste of what some local species on the coast of Vancouver Island have endured since European green crabs arrived.

These pernicious predators wreak havoc on the coast. They tear up eelgrass beds that nurture juvenile salmon, feast voraciously on clams and mussels, and push local shore crabs from their habitat.

Over the last 14 months, Coastal Restoration Society, a non-profit focused on environmental remediation, has been working with Fisheries and Oceans sa¹ú¼Ê´«Ã½ and Ahousaht, Tla-o-qui-aht and T’Sou-ke First Nations to remove invasive green crabs from their territories.

Almost half a million have been lured into commercial style prawn traps with pieces of frozen herring, their flat, jagged little bodies packed into large tubs and delivered to industrial freezers, where they are flash frozen in an icy death. Until early last summer, many were then left to rot at the landfill.

That didn’t sit right with Ahousaht Tyee Hawiih Hasheukumiss.

“What a waste of protein that we’re throwing out the door,” he said in an interview.

Green crab may be an environmental blight, but they’re also edible. At a time when inflation has driven up the price of groceries and food banks are seeing record demand, Hasheukumiss doesn’t see the sense in throwing out food.

The three First Nations and Coastal Restoration Society are urging Fisheries and Oceans sa¹ú¼Ê´«Ã½ to review its policies for what happens to invasive species after they’re removed from an ecosystem. Ultimately, they want the government to lift restrictions on Coastal Restoration Society’s licence and give the nations authority to decide what happens to the piles of European green crab pulled from the ocean.

Hasheukumiss said they did get approval to use the green crab for fertilizer — soon the nation will use thousands of pounds of invasive crabs to fertilize trees that struggled to grow after being planted in a logging cut-block in Ahousaht territory.

But for the moment, Fisheries and Oceans sa¹ú¼Ê´«Ã½ isn’t allowing anyone to eat the crabs the trapping teams catch. That was a “bit of a blow,” Hasheukumiss said. But he’s not giving up just yet: “I feel that we’re going to win this one.”

In a statement to The Narwhal, Alexandra Coutts, a Fisheries and Oceans sa¹ú¼Ê´«Ã½ spokesperson, said European green crabs are considered a type of shore crab. Under federal law, recreational or Indigenous harvesters can take shore crab for food with the appropriate licence or approval.

At this point, however, no commercial or scientific licences for the harvest of European green crab for human consumption have been issued in British Columbia or within sa¹ú¼Ê´«Ã½, she said.

Hitchhiking and surfing the waves, green crabs spread around the world

European green crabs, which are native to Europe and North Africa, likely reached North America in the early 1800s as stowaways on ships that crossed the Atlantic.

The crabs are now well established on the east coast, where they’re taking a toll on commercial fisheries.

Brenda Viscount, a Newfoundland fisher and field technician who collects green crabs for a mitigation program, said even after years of trapping, it’s a struggle to keep pace with the spread. But without such programs, the crabs would cause even more destruction, Viscount said.

Already, the feisty invaders have pushed out smaller lobsters in some areas, while in others, the seafloor is littered with empty clam and mussel shells, the remains of a feast.

“They’re very aggressive creatures,” Viscount said. “You can turn one bottom up and in a split of a second that crab is right back on its legs again.”

Yet, “you turn a rock crab bottom up and it will probably die bottom up because it can’t turn over,” she said.

In other words, green crabs are tough, which is why they’re successful invaders.

By the 1980s, the crabs reached California, this time hitchhiking aboard ships traversing the Panama Canal. From there, they rode ocean currents north.

Green crab populations balloon and spread easily — females can release up to 185,000 eggs each time they spawn. Their larvae drift in the water for weeks before settling in the shallows along the coast.

They’re a hardy species, but they thrive in sheltered estuaries where rivers empty into the ocean, where there’s soft sediment to burrow in and there are eelgrass meadows lush with food.

“The deep inlets of Clayoquot Sound, for example, make the perfect habitat for green crab,” said Crysta Stubbs, a senior project manager and lead biologist with Coastal Restoration Society.

Put enough of them together and these relatively small crustaceans can “completely transform an estuary,” she said.

In some places on the southwest coast of Vancouver Island where the crabs have been found for decades, it’s already happening. There are eelgrass meadows in Barkley Sound, for instance, that have disappeared in the wake of a green crab invasion, said Thomas Therriault, a Fisheries and Oceans sa¹ú¼Ê´«Ã½ research scientist.

Local Hemigrapsus shore crabs, once abundant, are now harder to find.

“It used to be you’d flip a rock and you’d be like: ‘Oh a bunch of Hemigrapsus scurry out,’ ” Therriault said. “Now, you flip lots of rocks on those same beaches and you don’t see any Hemigrapsus.”

Hasheukumiss said the green crabs are pushing out natural species, such as Dungeness crabs, which are culturally and economically important to Ahousaht First Nation. They’re not only food but a source of jobs and revenue through the commercial fishery.

According to Therriault, green crabs seem to thrive in less salty water than local species like Dungeness, meaning they can get a foothold in areas with little competition. Once established, they expand into deeper, saltier water, pushing native species out.

Green crabs aren’t picky eaters. They feast on everything from plants and detritus to worms, clams, snails and slugs, Therriault said. They’ve even been known to devour the young of other crab species.

Their presence also threatens wild salmon, already overburdened by warming waters, pollution and habitat destruction. The invasive crabs mow down eelgrass meadows, snipping the grasses as they forage for shellfish buried among the roots.

For juvenile salmon that shelter, feed and grow in these meadows before they’re forced to contend with the myriad risks of the open ocean, losing eelgrass nurseries can be calamitous.

Green crabs moving farther north as climate change drives marine heat waves

So far, established green crab populations in sa¹ú¼Ê´«Ã½ have been found off the coast of Vancouver Island, but they’ve been sighted as far north as Alaska.

In the past, green crab larvae, thwarted by the cold, struggled to reach these northern areas, Therriault said.

But as the climate crisis intensifies marine heat waves, “larvae are just riding those northward flowing currents into areas that otherwise they wouldn’t have had access to,” Therriault said.

Climate change might also make it easier for the crabs to sneak into the Salish Sea, the waters between the southern half of Vancouver Island and mainland sa¹ú¼Ê´«Ã½ and Washington.

Ocean circulation patterns have so far protected the Salish Sea from a major incursion, Therriault said — larvae from established green crab populations nearby are typically pulled away from the Salish Sea, not into it.

During those times of year when the flow reverses, it has typically been too cold for any larvae pulled in to survive, he said. But warming waters increase the chance that any larvae that do drift into the Salish Sea not only survive, but thrive.

Monitoring, control trapping best bet for controlling green crab spread

There’s little hope of eradicating green crabs from the west coast of North America. However, there are options for controlling populations to reduce their impact on ecosystems.

Fisheries and Oceans sa¹ú¼Ê´«Ã½ is working with First Nations and community groups to establish a monitoring network to track the crabs’ spread.

Similar efforts are underway in Washington state, where green crabs have been declared an emergency. Officials in sa¹ú¼Ê´«Ã½ and the U.S. are working in tandem to manage the problem, recognizing that as far as green crabs are concerned, the border doesn’t exist.

There is some hope. Early results from Coastal Restoration Society’s pilot program in Ahousaht, Tla-o-qui-aht and T’Sou-ke territory show commercial-style trapping can help control populations.

The teams trap five days a week in estuaries at the mouths of salmon-bearing rivers where green crabs have established populations.

They trap at four sites a month on each coast, spending a week at each location. On Mondays, they bait their commercial prawn traps with frozen herring and drop four lines of 10 traps in that week’s estuary.

The next day, they pull the traps, return any local species to the water, and count and measure the green crabs before piling them into totes. They bait and reset the traps and carefully rinse the boat and bilge to prevent further invasive spread.

From there, the crabs are sent to the freezers. Crabs from Sooke are later composted, but the piles removed from estuaries on the west coast are no longer sent to the dump. For now, they’re stockpiled in an industrial freezer with the idea that one day they’ll be used for something.

Results from the first year of trapping are still being compiled, but there are early signs it’s making a marked difference.

Teams pulled 8,000 to 10,000 green crabs a day from the Cypre River estuary in Ahousaht territory in the first few weeks of trapping, according to Stubbs. Hasheukumiss called those numbers “pretty shocking.”

More recently, though, they’ve caught fewer than 3,000 a day on average from the site.

“We certainly are making a difference,” Hasheukumiss said.

Coastal Restoration Society is trying to secure funding to expand the program. The trick is choosing where else to trap.

“There are just thousands and thousands of places where green crab could be,” said Alex Davis, an ecologist and post-doctoral fellow at the University of California Los Angeles.

To help figure out where to trap, Davis surveyed scientists, government officials, Indigenous communities, environmental groups and concerned citizens from California north to Alaska.

She asked respondents about the economic, ecological and cultural resources they value, from Dungeness crab fisheries to ancestral sites to areas of high biodiversity. “Everybody cares about seagrass,” Davis said.

These coastal meadows are held dear not only for the seagrass itself but also the species they support.

What’s not clear is where all the seagrass meadows are. Mapping meadows, mussel beds and other important areas could help governments make the best decisions about where to monitor and trap for green crab populations as the invasive crabs continue their insidious spread.

But what to do with the masses of crab removed?

Green crabs make a ‘tasty bisque’ and a ‘briny’ whiskey

Not long ago, Hasheukumiss — with 40 or so green crabs in hand — looked to his mother and said: “Let’s look up some recipes.”

During their molting stage, when their shells are still soft, green crabs can be eaten whole. But even once their carapace has hardened, the crabs can still be used in soup.

“When we did an experiment and my mother made up a batch, we kind of looked at each other and we’re like: ‘This is very tasty,’ ” he said. “Why are we wasting this?It seems such a shame. Even if it’s invasive, it’s edible.”

In New Hampshire, a distillery teamed up with researchers to produce green-crab-flavoured whiskey, a “salty, briny type of whiskey,” according to Davis. From New England, there’s even a green crab cookbook. Scientists have also looked at using green crabs for bioplastics or fertilizer.

Though Coutts, the Fisheries and Oceans sa¹ú¼Ê´«Ã½ spokesperson, warned that “any capture, transport or use of [European green crab] for any purpose, including use as fertilizer, poses a risk in terms of promoting their spread,” there are signs sa¹ú¼Ê´«Ã½ is changing the way it deals with aquatic invasive species.

The government is working on an approach to assessing the risk of spreading invasive species when considering ways to use them, or different methods to dispose of them, she said.

When that’s done, Fisheries and Oceans sa¹ú¼Ê´«Ã½ will be able to develop “appropriate licensing conditions” to mitigate those risks, Coutts said. She added that they expect to test a draft approach to permitting the use of invasive species in sa¹ú¼Ê´«Ã½ in the coming year.

“In theory, being able to use an invasive species as a resource is an amazing idea, especially in the numbers that we’re seeing,” said Davis, the University of California ecologist. “This was perfect for lionfish.”

In Florida, the Bahamas and other areas, people have been spearfishing invasive lionfish for years.

Lionfish don’t look like any local fish, so they’re easy to spot, and they’re fished one at a time, eliminating the risk of bycatch, said Davis.

With green crabs, however, it’s not that simple, she said. To the untrained eye, green crabs can be difficult to distinguish from local shore crabs. For one thing, green crabs aren’t always green and sometimes local species are.

Therriault said one of the clearest ways to identify the invasive species is to count the number of pointy spines the crab has on either side of its carapace. Green crabs have five.

But Davis warned that can be a little complicated too — what if the shell is damaged?

For the trappers working to catch green crabs in Ahousaht, Tla-o-qui-aht and T’Sou-ke First Nations territory who know how to identify them and safely return any local crabs caught in the traps, the answers may be more straightforward. They’re already catching tons of green crab — tens of thousands are sitting in a freezer right now.

The “sticking point” is likely around the broader policy questions, Davis said, like what happens when other groups want to start catching green crabs, too — and how to ensure they don’t accidentally start pulling local species from coastal waters en masse or unintentionally spread green crabs to new areas.

While some may question whether there’s potential for a commercial fishery, particularly in areas on the east coast where green crabs are firmly established, Fisheries and Oceans sa¹ú¼Ê´«Ã½ has said that could also raise the risk of spread.

Internal government documents obtained through an access to information request show the national fisheries intelligence service assessed the idea of opening a commercial harvest for European green crab and recommended against it, saying it would pose a high risk of “aquatic invasive species spread to unaffected areas.”

The potential for economic gain could encourage risky behaviour, it noted — for instance, moving invasive crabs to new areas to start a population to harvest for profit.

The report notes that there is a need for “continued effort towards systemic removal of the species to limit its spread.”

“The European green crab appears here to stay,” it says. “However, its continued presence will certainly lead to economic and environmental consequences.”