It feels like just yesterday when a video of a writhing bucket of oversized polychaetes marked the first catch of the light trap project at Miners Bay.
Whether or not that video was the best marketing choice to attract citizen scientists is up for debate, but despite (or because of?) the sea worms, a group of nine Mayne Islanders joined volunteers from all over the Salish Sea in the successful completion of the first year of the light trap project – a Dungeness crab larvae monitoring effort led by the Hakai Institute.
A little bit like the crab version of Ducks Unlimited, this project started in Puget Sound when fishermen and scientists recognized the need to formulate a species management plan to protect the upward of $70 million/year industry that is crabbing. Currently, there is no data-driven plan to leave enough crabs in the ocean to sustain a healthy population. Federal and local governments along with Hakai, the Pacific Crab Network, tribal leaders and a handful of other partners, aim to change that.
This is a multiyear project, with the objective to establish baseline data for the Salish Sea – sharing information with researchers across the entire network of traps.
How does the light trap work?
The light trap itself is based on a design perfected by researchers in the Pacific Crab Network in Washington State, USA. The trap is a fairly simple apparatus consisting of a 5-gallon spring water bottle with eight funnels on the sides and a buoyant bucket on top. This inverted bottle floats near the surface, attached to a dock, with a battery-powered LED strip light fixed in the centre. The light shines from sunset to sunrise and attracts many marine invertebrates, including crab larvae. Once in the trap, the creatures filter down into a screened collection canister which is then observed and documented by the volunteers.
I absolutely loved checking the light trap every week, and my 7 yr old son never failed to remind me when Wednesday came around. It was so exciting – not knowing what strange and beautiful animals will have ventured into the trap while it was dark (and the polychaetes only made me gag once).
The sample was often teeming with microscopic life: juvenile shrimp in bright red, lime green and transparent, several types of segmented marine worms of red, black, and yellow (some with crazy fangs!), many varieties of transparent juvenile fishes, different species and colours of crab larvae, and even sometimes baby octopi and squid. The days the trap was full of too many baby Dungeness to count really made you feel hopeful for the future.
What does a crab larvae look like?
After Dungeness crab eggs hatch, the first mobile stage of the life cycle – the Zoea – look like a helmeted space-shrimp with a big spike on their heads.
The second larval stage – the one we were looking for – was called the Megalopae.
Megalopae look like transparent miniature crabs, about the size of your pinky nail, with huge blue/black eyes and a tiny lobster-like tail. (CUTE!)
Able to travel huge distances in the few months they are floating around in the ocean currents, the Megalopae are surprisingly good swimmers. Their size can vary quite a bit, their shell measuring approximately 2 – 6 mm across. Once you see them for the first time, they are easy to differentiate from the other species of crab.
After the Megalopae molt into instars, the baby crabs become bottom dwellers. Once living on the bottom, the crabs still have about 4 years before they reach catchable size – giving you lots of time to stock up on butter.
Post-Season Gathering on Quadra Island
After the conclusion of the first season of data collection in the northern part of the Salish Sea, the Hakai Institute hosted a gathering at their incredible ocean research facility, the Quadra Centre for Coastal Dialogue on Quadra Island. Volunteers were invited to come together and discuss the project, hear from scientists and researchers, and give feedback and suggestions.
Scientists from Hakai held group discussions about the season highlights and some initial data analysis. The group also heard from Emily Buckner from the Pacific Northwest Crab Research Group, where light trap monitoring was first started. Now, for those of you new to the Hakai Institute, it was incredible to see this operation. Their research facility had beautiful houses for meetings, accommodation, labs and microscopy facilities, all in West Coast-style buildings seamlessly incorporated into the landscape.
It was clear to see why this magical place attracted so many wonderful people – from the researchers themselves to the onsite events coordinators, lab managers and incredible chefs.
The Dungeness Crab Monitoring project is part of the Sentinels of Change program by the Hakai Institute, which they describe as a decade-long community-centered initiative investigating patterns of invertebrate biodiversity, change and resilience across the Salish Sea.
If you didn’t get a chance to volunteer this year, I hope when the time comes next spring you’ll put your name forward. A special thanks to Katie Kushneryk, who led this project for the Conservancy and was a curious, inspiring and enthusiastic coordinator!
0 Comments