PSI researcher, Andy Suhrbier helps shellfish growers adapt to changing ocean conditions.
LIGHT TRAP MONITORING
Follow our light trap team each season as we search for tiny Dungeness crabs!
What is a Light Trap?
Our light trap is featured in the image below. It has a large float on top to keep the trap upright in the water and a weight at the very bottom to keep the large jug (yes that's a 5-gal water jug!) submerged in the water near the surface. Large funnels are attached to the sides of the jug that allow animals to swim in, but not out. At night, the timer inside the trap turns on a strip of led lights, attracting animals to the trap that exhibit positive phototaxis, attraction to light! When we pull the trap out of the water, the sample drains through a filter attached to the bottom of the trap, called the cod end. The cod end helps filter the water out, but collects the tiny crabs we want to see and count!
This style of light trap was designed by marine scientist, Dr. Alan Shanks to study larval Dungeness crab on the outer coast of Oregon and Washington. Biologists from the Swinomish Indian Tribal Community standardized the design for research purposes throughout the Salish Sea. Our trap is located in the Nisqually Reach at Zittel's marina in South Puget Sound. Our team of biologists monitor the light trap each year, April - September. Photo credit: Debbie Preston
What are we looking for?
We have joined biologists and community scientists throughout the Salish Sea (WA and BC, Canada) to participate in annual, long-term monitoring of juvenile stages of Dungeness crab, including megalopae (below) and instars. Data collected from April - September helps us learn more about the species, dynamics of early life stages and implications for adult crab populations.
A Dungeness crab in the megalopa larval stage. Relatively large compared to other crab species, their carapace width ranges from 3.5mm to 4.6mm. Photo: PSI
Why is it so important?
Recent declines in adult Dungeness crab in Puget Sound prompted the formation of the Pacific Northwest Crab Research Group (PCRG) in late 2018, led by treaty tribes and supported by state and federal agency biologists, university scientists and non-profit organizations to provide science-based information for adaptive planning and management of this species.
Fishing pressure and impacts of climate change, including low pH, warming temperatures and low dissolved oxygen, are among the drivers implicated in recent recruitment failures and smaller adult populations. Collecting information on the early life stages of the Dungeness crab will help inform and forecast how healthy adult populations are throughout Puget Sound and the broader Salish Sea. Monitoring a keystone species, such as the Dungeness crab, provides a big picture view of how the rest of the ecosystem is doing. Changes in adult populations and fisheries management of this species has broad economic and cultural impacts. Many communities in the Pacific Northwest rely on Dungeness crab for their livelihood, food security and cultural traditions. Through diverse partnerships, the light trap study aims to fill data gaps to support the sustainable management and harvest of Dungeness crab in the Salish Sea for current and future generations.
Fantastic work from Komachin Middle School 7&8th grade students working on, "Tiny Crabs, Big Impacts" curriculum! Thank you Katie Standlea for introducing your students to the Dungeness crab fishery and monitoring efforts in Puget Sound! We love seeing your students work! Photo: Katie Standlea
MS SCIENCE CURRICULUM
Are you a Middle School Science Teacher that wants to bring REAL DATA into the classroom? Look no further! PSI developed the curriculum entitled, "Tiny Crabs, Big Impacts: Long-Term Monitoring for Healthy Dungeness Populations", for Grades 6-8 (WSSLS/NGSS). Students will work through South Sound light trap data to understand how scientists are collaboratively monitoring a critical Puget Sound fishery. Explore the info below!
Kozloff, E. N. 1996. Marine Invertebrates of the Pacific Northwest. University of Washington Press. 552 pp
RECENT MEDIA
Researchers use light traps to illuminate Dungeness crab decline. KING5. Mar. 19, 2024. Article.
Pacific Northwest Crab Research Group researches dungeness crab populations and their implications on sustainable fishing in Washington. The Daily. Feb. 7, 2025. Article.
A Crab Network is Connecting Communities and Generating Crucial Data for Salish Sea Fisheries. UW School of Aquatic and Fishery Science. Jan. 24, 2025. Press Release.
