tiny crabs, big impacts: long-term monitoring for healthy
TRANSCRIPT
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Tiny Crabs, Big Impacts:Long-Term Monitoring for Healthy Dungeness Populations
Katie Houle and Rachel Hardin
Photo: Claire Cook-SITC
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Dungeness Crab in Washington
Photos: Jim Gibson
Most profitable fishery in WA State
• Co-Managed by State and Treaty tribes
Cultural Importance
• Tribal harvest and recreational fishing
Ecological Role
• Key predator (adult) and prey (juveniles) –
food for salmon and rockfish
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Biology and Ecology of Dungeness Crab
• Cancer magister
• Order Decapoda – 10 legs!
• Chelipeds = claws
• Carapace = shell, size determines age
• Live for about 8-13 years
• Harvest size at 4 years, 6¼’’ shell width
• Molt shells when grow too large
Photos top to bottom: ODFW
Crab molt (exuvia)
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Photos L-R: SF Chronicle, Scott Groth/ODFW, Vancouver Aquarium, WDFW
HABITAT PREDATORS
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Life Cycle of Dungeness Crab
Photos L, Top, Bottom: PCRG, SITC, ODFW
Female with Eggs
Megalopa stage
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Threats to Population
• Fishing Pressure
• Daily limits set during seasons, “3S system”
• Catch record card required in Puget Sound Fishing areas
• Climate Change
• Ocean warming and acidification
• Low dissolved oxygen (hypoxia)
• Vulnerability of larvae to disease
• Human Development
• Dredging- sedimentation
• Pesticides and other pollutants
Photo: Top: https://www.seattlemag.com/article/ocean-acidification-global-warmings-doppelg-nger; Bottom: Swinomish
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• Diverse group of researchers:
• State and Tribal Co-managers
• Federal Agencies
• Academics
• Non-profit Organizations (ex. PSI)
• Formed 2018
• Support sustainable fishing and healthy Dungeness crab populations in PNW
• Long-term monitoring in Puget Sound
Pacific Northwest Crab Research Group
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WHY?
• Recent declines of Dungeness crab in Puget Sound
• South Sound fishery closed since 2018
• Young crab are most vulnerable to stress in the environment
• Cause of declines still unknown…
Light Trap Monitoring Project
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Light Trap Monitoring Project
• Light traps deployed off docks and piers
around Puget Sound to capture larval crab
• Collect data April through September
• Megalopae swim to surface at night to feed
• Attracted to light of trap (phototaxis)!
• Other species attracted too…
Video: Megalopae in light trap - PCRG- Swinomish
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Light Trap Monitoring Project
1. Identify and Count Crabs 2. Measure Dungeness Crabs
3. Record data!
Photos: PCRG – Swinomish
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Light Trap Monitoring Project: Crabs
Cancer Gracilis
Crab Zoea
Instar
Dungeness
Photo: Jamestown S’Klallam
Photo: Shannon Boldt
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Light Trap Monitoring Project: Other Species
Crangon
Cumacean
Sand Shrimp
Hyperiid Amphipod
Photo: M. Homerding
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Snake Prickleback
Gunnel
Light Trap Monitoring Project: Other Species
Baypipe Fish
Clingfish
Larval Forage Fish
Juvenile English Sole
Photos: M. Homerding
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Light Trap Monitoring Project: Other Species
Polychaete
Octopus Larvae
Jellyfish
Pile Worm
Squid Larvae
Nereid Epitoke
Photos: S. Boldt
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Take Home Messages
• Dungeness crab of all ages are important parts of our
ecosystem
• Washington communities rely on Dungeness crab for
their livelihood, food, culture and fun!
• Cause of recent declines in Puget Sound unknown…
• Climate change negatively impacts Dungeness crab
• Scientists are working together to learn more so we
can keep fishing Dungeness crab sustainably in WA!
Photo: Jamestown S’Klallam
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Quick Quiz!
1. Name one reason Dungeness are important in Washington?
2. Where can we find Dungeness?
3. Who preys upon Dungeness?
4. What are some threats to the population?
5. What year did the South Sound Dungeness fishery close?
6. Why are we using the light traps?
7. Can you name other species found in the light trap?
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A BIG THANK YOU!
Pacific Crab Research Group
Our funders – Keta Legacy Foundation, The
Russell Family Foundation, and the Squaxin
Tribal Community
Our South Sound Partners- Nisqually Indian
Tribe, Nisqually Reach Nature Center, WDNR
Aquatic Reserves Program, and Zittel’s Marina
for hosting our light trap
Photo: Zittel’s crew checking out the catch!