European Green Crab project 

Photo caption: ED Karen Wristen was actually grateful that there weren’t hundreds of crabs needing their carapaces measured—they're slippery, squirmy beasts! 

We’ve been tracking European Green Crab incursions into Northwest Vancouver Island for some time now. We first noticed them in Sea Otter Cove, where they were devastating the formerly extensive eelgrass beds. An invasive species native to Europe and Africa, these crabs have travelled the world, outcompeting native crabs and wreaking havoc with habitat. 

We think they arrived in Sea Otter Cove as early as 2016, when we noticed the tide line: it looked bright orange from a distance. On close observation, the wrack was filled with thousands of tiny Dungeness crabs, each with a hole punched through its shell. This is one way the invaders make themselves at home. 

Again in 2022, while our crew cleaned the beach at Laura Creek, we observed juvenile green crab numbering in the hundreds, scuttling about on the beach and in the tide pools. We reported the sighting to the Department of Fisheries and Oceans (DFO) but being without a licence to trap them at the time, we did not take samples. 

This year, we determined to check to see how far up the Island the crabs had moved. We applied for a scientific licence from DFO. We mounted 3 crews: one back at Laura Creek, one at Shuttleworth Bight and another at Nahwitti River. All of these sites are on the North Coast Trail and highly exposed to the open Pacific, but all also have fish-bearing rivers. The crabs are known to travel upriver to feed on fish eggs and fry, so finding how far they have spread is important to protecting wild fish populations. 

Each crew was equipped with 2 crab traps and 2 minnow traps, plus gear to bait, anchor and retrieve their contents. At all locations, there were 2 rivers to monitor. We were time-limited, performing the work while encamped remotely and cleaning beaches at the same time. Each river was accordingly sampled with one 24-hour set. All of us found the sea conditions challenging for the setting of traps: the surf was high and active. The traps had to be weighed with rocks as well as anchored with rebar and/or rope. 

In the result, one lone male EGC was trapped at the Strandby River. Very few crabs of any description were found on any of the beaches, including Laura Creek. We found that odd, given what we’d seen in 2022, but perhaps conditions have been sufficiently rough that the crabs decided to move on. 

It would be worth another sampling event at the Strandby River. The habitat there is promising for crab, with extensive beds of eelgrass and other seaweeds. The adjacent beach (Shuttleworth) showed evidence of juvenile Dungeness with fractured shells, similar to what we’d seen at Sea Otter Cove (although in much smaller numbers). We will need to have a small vessel available to manage the sets in the best possible locations—something we couldn’t do this year for lack of funding. 

We will be reporting the results to Quatsino and Tlatlasikwala First Nations, to see if they are interested in working on a proposal to trap out the invaders. Other First Nations, working on Southwest Vancouver Island, have been running an eradication program for several years now. They have reported recovering multiple thousands of crabs per set in some locations, so getting on to the work while populations are still relatively small may be the key to preserving local biodiversity.

Photo caption: Volunteer Patrick Savage braved the surf to set the traps, but carrying everything to the lowest low tide line was a group effort.