ACAP trapping green crab to try and eradicate the invasive species from the Bay of Islands

Diane
Diane Crocker
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During the first two weeks of July a crab harvest in the Bay of Islands resulted in a catch of 400.

Might not seem like much if you were a fisherman trying to make a living, but the crabs caught were not the ones that will end up on someone’s dinner plate.

They were green crabs, an invasive species that is aggressive in nature in that they force other species out of an ecosystem and also destroy habitat. That’s why reducing their numbers has become a project for ACAP-Humber Arm.

Last year ACAP worked in partnership with a number of organizations to study the presence, abundance and distribution of green crab in the Bay of Islands.

Sheldon Peddle, executive director of ACAP, said the study found that green crab are here in larger numbers than was anticipated.

“They’re wider spread throughout the bay,” he said. “As well they’re found further in the bay than was expected.”

Peddle said that’s a bad sign.

“For them to make their way this far in the bay means they have in fact been here for years, that the populations are established, that they’re reproducing and they’re expanding their range.”

So armed with the information from the study, ACAP started eradication efforts and captured 2,190 males and 465 females last year.

The captured crabs were taken from traps, frozen, examined to collect data and then sent to a composting facility in Stephenville.

Peddle said a late start last year may account for the low female numbers, who were probably past their fertilization period when the trapping began.

“When the females become fertilized, when they’re carrying their eggs, they tend to hide and they become very inactive,” said Peddle. The females will bury themselves in the sand which makes them harder to trap and if there are two or three males already in a trap the females won’t go in.

“So most of the females we captured last year were at the end of the year after they had already released their eggs.”

Peddle said the trapping started earlier this year to get as many green crab out of the water as possible and to capture the females before they release their eggs.

The plan is paying off.

“In some cases the number of females we captured at some sites outnumbered the number of males, which is very odd, but very positive. Because it means we got them while they were still active, before they were carrying eggs.”

That’s good news as one female can release between 150,000 and 200,000 eggs per year.

Peddle said the focus for this year is on sites in the inner, outer, north and south shores of the bay where the greatest numbers were found last year. So far green crab have been collected from 19 of 23 sites.

Peddle said the project is on a break now as ACAP moves into an eelgrass project and will resume again later next month and continue into the fall. He said the plan is to explore some other sites where green crab have been found including Wood’s Island and Middle Arm.

The green crab project is a partnership between ACAP, Environment Canada, the federal Department of Fisheries and Oceans and the provincial Department of Fisheries and Aquaculture. This year the captured crabs are being disposed of in the industrial composter at Grenfell Campus, Memorial University of Newfoundland.

Sites where green crab have been found:

Lark Harbour

Bay of Islands Marina

Brake’s Cove

Church Cove

Corner Brook waterfront near RA Pollett Building

Corner Brook waterfront near wildlife building

Summerside (2 locations)

Irishtown

Meadows (2 locations)

McIver’s

Cox’s Cove

Irving Oil Tank farm, Corner Brook

Cook’s Brook estuary

Bannatyne Cove

Gillams (2 locations)

Wildcove

Source: ACAP-Humber Arm

 

Data

After the green crab have been captured they are examined at the ACAP office and the following information is recorded and shared with the provincial and federal fisheries departments:

Gender

Carapace length

Propodite length

Propodite width

Propodite location

Abdomen width

Carapace colour

Abdomen colour

The information gives an indication of how established the population and its health.

Source: ACAP-Humber Arm

 

Organizations: Environment Canada, Department of Fisheries and Oceans, Department of Fisheries and Aquaculture Memorial University of Newfoundland

Geographic location: Bay of Islands, Iceland, Middle Arm

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