Last April, Cortes Island became part of an international monitoring project for Dungeness crab larvae. There were 20 light trap stations in the Salish Sea and 17 in the Puget Sound. Three of these traps were within our  listening area. Surge Narrows School had a trap on Read Island. The Hakai Institute and Quadra Island community had another on Quadra Island. Kate Maddigan and Mike Moore coordinated volunteers looking after the Friends of Cortes Island (FOCI) trap in Cortes Bay. 

“Hakai and the Pacific Northwest Crab Monitoring Group are working in concert with each other to provide data as to what is happening to the larval Dungeons Crab populations.  It’s been happening in Puget Sound for a few years. They have about five years of data down. Dungeness Crab fishing is one of the most lucrative and important crab fisheries on the coast.  Catches have been diminishing, this is an effort to find out why,” explained Moore. 

He added that the first phase of this project came to an end in August. 

“Our Cortes Bay trap had very promising results to start with, then the warm fresh water layer moved in. That warm fresh water layer is what makes Desolation Sound so famous and warm for swimming in, but it  doesn’t support marine life very well. In fact, if you jump into the water, in say July, and swim down sometimes 7 meters that’s where you’re going to find the moon jelly fish. They’re not up in the warm, fresh water.  Our trap that floats at the surface was encapsulated by this warm fresh water and our results really diminished.” 

They only caught ‘a handful’ of statistically valuable megalope (the stage during which the young Dungeness Crabs become recognizable as crabs).

“The day we caught the most didn’t count. We had pulled the trap, I’d taken off the bottom and emptied it into our container to count.  We’re looking at the Pipefish and the big Polychaete Worms and all that sort of thing, looking for crab larva,” said Moore

“We didn’t find any and then (my son) Fergus Walker, who was with me that day,  goes, ‘What’s that?’ and I look on the outside of the trap and we counted, I think it was 44 Dungeness Crab megalope. Those are the first ones we caught, but they didn’t count because they weren’t inside the trap. It’s not statistically significant because they weren’t inside the trap, but for us it was pretty significant.”

According to the Light Trap Station map, on Hakai’s Sentinels of Change page, 11 Dungeness Crab megalope were caught on Quadra Island, 20 on Read Island and 74 on Cortes Island.

The teams posted pictures of other larvae they captured on the Hakai website. 

“I posted some photos that I took just with my iPhone of Stubby Octopuses, what we think  are Opalescent Squid,  Grunt Sculpins, Sailfin Sculpin and Pacific Sand Lances. When I took their pictures, they were in a plastic teaspoon for scale.  They’re all tiny  and my gosh, they’re beautiful when they’re small. Flatfish, which I think were probably the larvae of Starry Flounders,  are perfectly transparent except for their guts  and gills and eyes,” said Moore.

“A lot of these creatures are really, really transparent in their larval stages and then they darken up later.  It was just amazing to see.  Being at the bottom of the food chain,  they need to do their best to camouflage themselves and transparency appears to be one of those ways.”

Moore said scientists do not know why the Dungeness Crab population in diminishing. There are a number of theories: 

“There’s not enough adult crabs to produce enough spa because of perhaps overfishing. The planktonic larval stages may be affected by ocean acidification and not being able to lay down their shell and grow properly. It could be temperature changes, it could be other chemical changes in the water. It could be a whole number of things that are affecting the crab population.” 

The light trap in Cortes Bay has an LED strip that lights up at night. 

“All kinds of plankton and critters were attracted to the light and found their way in through the intake funnels. Then in the morning we would   empty out the trap into a pan and see what we caught,” said Moore.

All of the light traps from Cortes, Quadra and Read Islands south to the Puget lit up on the evening of April 15 and the experiment lasted until August.

The Hakai Institute held a season’s end gathering on October 4 and 5th. Kate Maddigan and Mike Moore attended.

“We went over to the Hakai Institute on Quadra Island and were able to view some of the catch data. They had laid it out in terms of a graphic which showed how, starting from Juan de Fuca Strait and through the Puget Sound,  the larva showed up earlier in the season and then they worked their way up the East Coast of Vancouver Island and swirled around into Quadra and Cortes Island and then down the mainland coast towards Vancouver.”

The next phase of the project will try to determine the route. 

“They’re going to be starting to do genetics research on the larval crabs to see if they can identify different populations and where the larvae are coming from,” said Moore. 

During the mid 1980s he worked on a fishing boat based in Port Hardy. Moore was surprised to learn that the Dungeness crab on Cortes are not related to the population he fished in the Broughton Archipelago, but are coming from the Juan de Fuca Strait – Puget Sound area.  

“We are catching them at what’s known as the megalope based stage, they are already months old and they’ve already been drifting as smaller larvae in the ocean. This is stuff the scientists are just trying to get a grasp on, and they’ll do that through genetics if they look at the DNA sequencing of a larvae that’s caught in Cortes Island, and they may find that it is the same population as what Tofino has, or something like that,” said Moore.  

“How far they go as  a larvae is completely different from how far they’ll go as an adult too. I don’t know if anybody really knows how they migrate.  The adults definitely migrate up into the shallows off of Hernando Island and  I would suspect traditionally off of Marina Island.  All those sand ecologies and eel grass ecologies,  they would migrate up into there to mate in early summer, say May/June. You can find them in the shallows, but in the wintertime they go much deeper. I don’t know how deep.” 

Moore has been off island a great deal since last June, when he was employed by BC Ferries. However his partner Kate, son Fergus Walker and a number of neighbours are all involved in the project.

“We started the project before I actually got the job with ferries. So it was a big scramble. Fortunately, Kate’s really excited about this project as well.  She used to work with fisheries and  she’s done monitoring projects before.  It was always fun to bring Fergus and I know other people brought their kids out to see what was going on in the light trap,” said Moore.

“We had a really good backup, Barry and Carrie Saxifrage: naturalists, wildlife and life science enthusiasts. They were there to back us up when they were able.  The trap was actually kept at a private dock and when they were around, the  owners were really excited to help out as well. Monika Hoffman, Sadhu Johnston and Lorne Jacobson helped out.  Savana Young, who’s teaching the Cortes Island Academy right now, helped out. So through it all, we were able to do that.” 

Top photo credit: Dungeness Crab megalope in a teaspoon – Photo by Kate Maddigan

Sign-up for Cortes Currents email-out:

To receive an emailed catalogue of articles on Cortes Currents, send a (blank) email to subscribe to your desired frequency:

• Daily, (articles posted during the last 24 hours) – cortescurrents-daily+subscribe@cortes.groups.io
• Weekly Digest cortescurrents – cortescurrents-weekly+subscribe@cortes.groups.io