Souris wildlife group battles invasive green crab

A Souris wildlife group is trying to reduce the invasive green crab in the Basin Head marine-protected area. The crabs are threatening a unique Irish moss species that is only found in Basin Head.

Pilot project to count and destroy the invasive crustacean

Cheverie says the lagoon at Basin Head is crawling with these invasive green crabs. (Pat Martel/CBC)

An invasive species that has hit Eastern P.E.I. waters with a vengeance now has a new enemy. His name is Fred Cheverie — the watershed coordinator of the Souris and Area branch of the PEI Wildlife Federation. 

Cheverie is heading up an extensive 8-week research project to catch and document as many green crabs as possible in the Basin Head lagoon.

Fisheries and Oceans Canada is funding the $18,000 pilot project.

"The population has exploded here in Basin Head for sure," said Cheverie.

WATCH Crab's eye view


4 years agoVideo
WATCH Crab's eye view 0:48

Crabs destroying unique moss

Cheverie said green crab has almost wiped out a unique species of moss — the giant Irish moss. Basin Head is the only place in the world where the moss grows. 

The moss anchors itself to mussels, but Cheverie said hordes of green crab are eating the mussels, leaving the Irish moss to float away and die.

Fred Cheverie and his helpers set out 35 green crab traps daily to catch the crustaceans. (Pat Martel/CBC)

Cheverie and his helpers set out 35 green crab traps daily to catch the crustaceans. 

"We're catching about 1000 green crabs a day," he said.

A GoPro underwater gives a crab's eye view from inside one of the 35 traps set in Basin Head lagoon. (Pat Martel/CBC)

 "The whole idea is to try to find out how many green crabs are out there, can we catch them, what time of year, what areas of the watershed are they located, so we're continuously moving gear every day trying to catch the most we can."

Counting crabs

Cheverie said the aim is not just to remove as much green crab from the Basin Head waters as possible, but to also keep extensive records of every crab caught.

Cheverie says he and his two helpers catch about one thousand crabs a day. (Pat Martel/CBC)

"We have to take them back and measure, count every one, measure the carapace size and distinguish whether they're male or female. We also have to GPS each trap, where it's located, how much fish is caught in that trap," said Cheverie.

"We move gear daily, so it gives us an idea in the whole of Basin Head where the crabs are located, and what we're finding out is they're pretty well everywhere."

Some of the hundreds of crabs that are caught in the Basin Head lagoon daily. (Pat Martel/CBC)

The crabs are dropped into a fresh water vat where they die within 24 hours.

Cheverie said during the first few weeks of the project, the crabs were taken to a compost facility in nearby North Lake, but the road got too muddy. Now an organic farmer has agreed to take them. 

Deep-fried green crabs anyone?

Green crabs first appeared in P.E.I. in the 1990s likely brought here in the bilge water of boats from Europe. The eastern part of the Island has been hardest hit.

When asked why aren't the crabs eaten here, Cheverie replied, "Fill your boots if you wish to, but I'm not going to."

Fred Cheverie and his two helpers bag up another load of green grab that will end up in a field as compost. (Pat Martel/CBC)

"They're very small, a lot of work to get a bite to eat, but in Europe they are over-fished. They get them in their moulting stage, when the carapace is soft and they fire them in a deep fryer and basically eat the whole thing."

Research provides baseline

Cheverie said this research project has been the most extensive survey on P.E.I. of the green crab population. He said it will be a baseline to gauge whether the measures will work.

"By lowering the numbers of green crab in Basin Head, it should give the Irish Moss we're trying to rejuvenate a better chance," he said.

"Now you could probably gather it [Irish moss] all up and put it in a five-gallon bucket."

A GoPro captures the green crab underwater just before the workers haul in the traps. (Pat Martel/CBC)

About the Author

Pat Martel has worked with CBC P.E.I. for three decades, mostly with Island Morning where he was a writer-broadcaster and producer. He joined the web team recently to share his passion for great video. Pat also runs an adult coed soccer league in Stratford. He retired in Oct. 2019.