Invasive green crab widespread in Bay of Islands

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Group traps green crabs to try and erraticate invasive species from the Bay of Islands

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

David Goulding, a staff member with ACAP-Humber Arm, checks a trap for green crabs in the bay just east of the marina at the Bay of Islands Yacht Club on Wednesday. — Submitted photos

That might not seem like much if you are 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 as they force other species out of an ecosystem and also destroy habitat.

That’s why reducing their numbers has become a project for ACAP (Atlantic Coastal Action Program)-Humber Arm.

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

Sheldon Peddle, executive director of ACAP, said the study found that green crabs 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.”

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 crabs 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 crabs 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 crabs 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.

 

The Western Star

Organizations: Environment Canada, Department of Fisheries and Oceans, Department of Fisheries and Aquaculture.This Memorial University of Newfoundland.The Western Star

Geographic location: Bay of Islands, Iceland, Middle Arm

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