Shellfish Research and Information
Services for the U.S. West Coast

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Internships with PSI

Intern or volunteer on one of PSI's research projects or outreach campaigns.


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The man with a plan

PSI researcher, Andy Suhrbier helps shellfish growers adapt to changing ocean conditions.


Follow our light trap team each season as we search for tiny Dungeness crabs!

Light Trap Monitoring

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!

Light Trap

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 stage. Relatively large compared to other crab species, their carapace width ranges from 3.5mm to 4.6mm.

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.

Meet the team!

Margaret Homerding, Shellfish Biologist, Nisqually Indian Tribe

Shannon Boldt, Volunteer Biologist, Nisqually Reach Nature Center

Austin Greene, Aquatic Reserves Specialist, WA DNR Aquatic Reserves

Katie Houle, Senior Biologist, Pacific Shellfish Institute

Yvonne Shevalier, Volunteer Biologist, Pacific Shellfish Institute

QUESTIONS? Contact Us!


PCRG logo

Zittel's Marina, for hosting the South Sound light trap ('19-'24)

Nisqually Indian Tribe, funding support for PSI light trap monitoring ('22, '24)

Squaxin Island Tribe, funding support for PSI light trap monitoring ('19-'24)

The Russell Family Foundation, funding support for educational programming and light trap materials ('20,'21)

Keta Legacy Foundation, funding support for community science program and middle school curriculum design ('20)

Boston Harbor Marina, for hosting the PSI light trap ('20)

Tiny Crabs, Big Impacts Curriculum Student Work

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


Megalopae Icon

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!

Introductory Presentation (PDF)

Supplementary Notes (PDF)

WDFW Article (3/11/2020) (PDF)

Data Module (Graphing Activity)- Teacher Key (PDF)

Data Module (Graphing Activity)- Student Workbook (Fillable PDF)

Data Module (Virtual Classroom)- Teacher Key (PDF)

Data Module (Virtual Classroom)- Student Workbook (Fillable PDF)


Please contact PSI Biologist, Katie Houle for additional resources and curriculum support.



Collect your very own Critter Cards! Cards feature fun facts about animals we commonly find in our light trap. Save the cards in a "digital deck" or print at home!


Light Trap Common Species ID Guide

Crab ID Guide

Zooplankton ID Guide

Invertebrates of the Salish Sea

Kozloff, E. N. 1996. Marine Invertebrates of the Pacific Northwest. University of Washington Press. 552 pp


Bizzarro, J.J., Selleck, J., Sherman, K., Drinkwin, J., Hare, V.C., and Fox, D.S. 2022. State of the knowledge: U.S. West Coast nearshore habitat use by fish assemblages and select invertebrates. Portland, OR: Pacific Marine & Estuarine Fish Habitat Partnership. **Summary from light trap study, pp. 39

PSEMP Marine Waters Workgroup. 2021. Puget Sound marine waters: 2020 overview. **Light trap study featured, pp. 42

Houle, K. Homerding, M., Brownlee, A. and Boldt, S. 2021. Light Trap Monitoring for Larval Dungeness Crab. Project Summary. South Sound Science Symposium. Web.

Dungeness Instar

A Dungeness instar, the stage directly after the larval megalopae, caught in our light trap. Photo: K. Houle