Drop a light in a dark sea and a crowd starts to gather. The visitors who come to the show are planktonic larvae: young Dungeness crabs, along with tiny juvenile octopuses, squid, shrimp, and many other organisms. By suspending a light trap from an ocean dock—the traps are handmade from a water jug, a bucket, funnels, and an LED light—researchers and community volunteers are able to attract these organisms, trap them, and count them.
Light traps are one arm of the Hakai Institute’s Sentinels of Change research project, which explores the shifting dynamics of invertebrate biodiversity in the Salish Sea. Among the larval organisms that swarm the light traps, one is of particular interest to Sentinels participants: Dungeness crab megalopae. No bigger than a pinky fingernail, megalopae are juvenile crabs in the final swimming stage, just before they settle down to feed on the ocean floor—where they can grow to a shell width of over 20 centimeters.
Dungeness crabs are of major ecological and cultural importance on the Pacific coast. They have been an important food source for many Indigenous communities for millennia, and are one of the highest-value fisheries in both Canada and the United States. The constellation of community-deployed light traps in the Salish Sea provides a vital indicator of stock abundance.
The first Sentinels of Change light trap pilot kicked off in 2022. Since then, dozens of community partners and organizations—including Fisheries and Oceans Canada along with First Nations, environmental NGOs, school groups, and businesses—have joined in, adopting light traps made by Hakai Institute researchers. Participants deploy the traps, bring up their catch, and catalog the organisms before releasing them back into the sea.
As a community science initiative, Sentinels of Change encourages deeper relationships between coastal residents and the ocean, and the gathered data also helps scientists and managers develop critical baselines to track the general resilience of marine ecosystems in the face of climate change.
“The quality and amount of data that we’re able to collect is really remarkable,” says Alyssa Gehman, a Hakai Institute marine ecologist and one of the lead researchers of the project. “It’s been incredibly impressive to see how excited people are to do the work and the dedication they have to the project.”
Sentinels of Change is slated to last for another seven years. The Hakai Institute is part of the United Nations Decade of Ocean Science for Sustainable Development, and Sentinels embodies the spirit of international cooperation via its partnership with the Pacific Northwest Crab Research Group (PCRG) based in Washington State. PCRG has over 20 light traps deployed via tribes and other research partners in the southern Salish Sea.
Meanwhile, the program is expanding beyond light traps. A recent federal grant has provided funds for additional research, including environmental DNA (eDNA) sampling and bolting recruitment plates to intertidal rocks to attract species like barnacles and marine snails.
“We are just getting started on those aspects,” says Gehman, “but when you put it all together it starts to really create this informative picture, which relies on all these community volunteers coming together. It’s very inspiring.”
Read more about the Sentinels project in this 2023 Hakai Magazine feature.
