Crabs

Below are a few examples of crabs living on Oregon’s exposed rocky shores or beaches. The photos are from northern Oregon unless noted. These are the most easy-to-spot crabs I’ve seen and photographed on the shores I’ve visited—they’re the ones you can find with a light touch without turning rocks or creating disturbances. Organization-wise, I loosely follow Lamb and Hanby (2005). I refer to WoRMS for scientific nomenclature; if I use common names, they’re my choice. Experts cover these crabs and many more in the books, field guides, and identification resources listed at the bottom of the page.

Let’s explore some crabs!

Pachygrapsus crassipes, striped shore crab
They’ll challenge you, but in the end, they’re sweethearts.

A closeup looking down from above on a crab on bare rock.
They tend to scuttle away from approaching humans, but occasionally one will settle for a while
Closeup looking down on a bright shore crab on bare rock.
Green coloration can be striking
Looking straight at a brooding shore crab resting among a mix of barnacles.
This one was brooding eggs in July
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Cancer productus, red rock crab

Pinching claw closeup
The fabled red rock pinching claw | Orcas Island
Empty red rock crab carapace on the sand.
A drifted carapace
Underside of a red rock crab.
The underside isn’t particularly spotted (for comparison, see Romaleon antennarium below)
Red rock crab partially submerged and buried in sand.
Red rock crab partially submerged and buried in the sand.
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Romaleon antennarium, spot-bellied rock crab, Pacific rock crab

A close up view from above of a single crab with a clean, shiny shell. In seaweed. Low intertidal.
Romaleon antennarium \ Central Oregon
An upside down carapace with a missing abdomen showing red spots on the ventral surface.
Even with a missing abdomen, this molt illustrates why they’re called spot-bellies
Closeup on a single crab partially buried at the sand/rock interface.
Spot-bellies are buriers that favor a mix of sand and rock | Central Oregon
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Metacarcinus magister, Dungeness crab
Molted shells are abundant in the wrack. When the molt is in full swing, the beaches of some exposed shores become so littered with freshly molted shells it looks like a die-off.

The crab is facing away from the viewer, it's feet buried in sand and a few barnacles on it's shell.
Metacarcinus magister in a shallow sand-filled pool
Adult female, flipped over to show the underside; on wet beach sand
Female, flipped over to show the broad abdomen
Right side up carapace on wet beach sand
Drifted carapace still carrying barnacles
the whole exoskeleton with the carapace flipped over the top; on wet beach sand.
July molt | You can imagine a fresh Dungeness crab stepping out of this
Just a claw on clean dry sand, surf zone and a headland in the background
Dungeness pinching claw
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Pugettia producta, northern kelp crab

Pretty close up low, oblique view with surfgrass in the background
Northern kelp crab, Pugettia producta | Central Oregon
A kelp crab, backlit and dangling from a drapery of sea cabbage.
Backlit in the shade and shadows | Central Oregon
Dead male kelp crab, upside down carcass
Dead male (note narrow abdomen) | Galiano Island
Avian scavengers won’t turn down a kelp crab
Pugettia producta peeking out from beneath the kelp | Central Oregon
***


References

Gotshall, D. W. 2005. Guide to Marine Invertebrates, Alaska to Baja California 2nd Edition (Revised). Shoreline Press.

Harbo, R. M. 2011. Whelks to Whales: Coastal Marine Life of the Pacific Northwest. 2nd ed. Harbour Publishing Co.

Jensen, G. C. 1995. Pacific Coast Crabs and Shrimps. Sea Challengers, Monterey.

Kozloff, E. N. 1993. Seashore Life of the Northern Pacific Coast. 3rd ed. University of Washington Press.

Lamb, A. and B. P. Hanby. 2005. Marine Life of the Pacific Northwest. Harbour Publishing.

Sept. J. D. 2019. The New Beachcomber’s Guide to the Pacific Northwest. Harbour Publishing.


Online Resources

Biodiversity of the Central Coast’s Crustaceans page is full of great information on Pacific Northwest crabs. Accessed 01/12/2023.

Friends of Netarts Bay WEBS Crustaceans page. Accessed 01/12/2023.

It’s worth scrolling down to crabs in Common Sea Life of Southeastern Alaska: A field guide by Aaron Baldwin & Paul Norwood. Accessed 01/12/2023.

Cowles, D. (2005). Pachygrapsus crassipes Randall, 1839. Invertebrates of the Salish Sea. Rosario Beach Marine Laboratory. Accessed 03/13/2023.

Cowles, D. (2005). Cancer productus Randall, 1839. Invertebrates of the Salish Sea. Rosario Beach Marine Laboratory. Accessed 01/12/2023.

Cowles, D. (2005). Pugettia producta (Randall, 1839). Invertebrates of the Salish Sea. Rosario Beach Marine Laboratory. Accessed 01/12/2023.

Cowles, D. (2007). Romaleon antennarium (Stimpson), Schweitzer and Feldmann, 2000. Invertebrates of the Salish Sea. Rosario Beach Marine Laboratory. Accessed 01/12/2023.

Maxwell, J. (2002 as edited). Metacarcinus magister  (Dana, 1852) Schweitzer and Feldmann, 2000. Invertebrates of the Salish Sea. Rosario Beach Marine Laboratory. Accessed 01/12/2023.


I updated this page on January 12, 2023.