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 on the Oregon 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). 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 the crabs!


Hemigrapsus nudus Purple shore crab

Closeup of a purple shore crab Hemigrapsus nudus perched atop a smooth bare rock.
Head-on closeup of a purple shore crab Hemigrapsus nudus on sand at the base of a smooth rock.
Closeup of a small purple shore crab Hemigrapsus nudus on a smooth rock. The color is yellowish, rather than the usual purple.
Closeup of a small purple shore crab Hemigrapsus nudus on a the sand The carapace is dominated by light pink, purple, and green coloration. The legs are greenish.


Purple shore crabs live on the rocks and in rocky crevices, but during the lowest tides I’ve found plenty of them out on the sand in the early morning hours. I’ll probably never know if they’ve been on nocturnal excursions, or if keen-eyed birds hunting the low tides have dislodged them from their rocky perches.

Eye-level closeup of a purple shore crab Hemigrapsus nudus out on the beach.
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Pachygrapsus crassipes Striped shore crab

You may hear them scuttling over the rocks and away before you see them. Occasionally, mid-retreat, or, more likely, if cornered, striped shore crabs will pull up and briefly adopt a combative stance.

Closeup of a striped shore crab Pachygrapsus crassipes, pinching claws extended, seemingly ready for a fight.


Just seconds after the initial standoff, the same crab let me move in pretty close for a look at its beautifully-colored carapace.

Closeup of a striped shore crab Pachygrapsus crassipes on bare rock.


Finding that perfect niche

A closeup looking down from above on a striped shore crab Pachygrapsus crassipes in a water-filled niche on bare rock.
They tend to scuttle away from approaching humans, but occasionally they’ll settle within sight
A closeup of a striped shore crab Pachygrapsus crassipes wedged vertically in a vertical crevice in bare rock. The claws are prominent.
Those claws
An eye-level view of a brooding striped shore crab Pachygrapsus crassipes resting among a mix of barnacles.
This one was brooding eggs in July


Fitting in

Looking down at a striped shore crab Pachygrapsus crassipes nestled among tremendous mid intertidal seaweed and invertebrate diversity.
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Planes

Planes is an oceanic crab that you’re not likely to see on the shore unless they’ve washed in on a floating object. The crabs shown here—probably Planes minutus—were hiding in and under a well-developed community of pelagic barnacles inhabiting a beached buoy.

The panels below show the dorsal and ventral view of an adult female (note the broad abdomen in the right-hand panel), at least I believe it’s an adult, she’s up in that size range.

Dorsal view of an adult female Planes minutus.
Ventral view of an adult female Planes minutus.


Quite a few crabs arrived, along with a community of pelagic barnacles, on the do-it-it-yourself buoy seen in the top left-hand panel. The presence of various sizes was hard to miss. (The largest crab among those in the bottom panel is the female shown above.)

A lost do-it-yourself buoy rests on the beach. Surf zone in the distance. Cloudy sky.
Closeup of several pelagic barnacles Lepas attached to the webbing on a beached do-it-yourself buoy resting on the sand.
Planes minutus of various sizes.


Planes minutus, as its name suggests, is a small crab and I feel like this image, which I think is an adult female, puts that in perspective better than words can. (That carapace is only about the width of the nail on my middle finger.) After taking the photograph, I learned first-hand that these little crabs are clingers. It didn’t want to let go, so I let it crawl up my index finger, where it seemed quite at home, which is unlike other shore crabs I have known, which don’t seem at all at home on fingers. Pulling it off was a task. These drifters are meant to stay on.

Closeup of a hand-held Planes minutus.
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Glebocarcinus oregonensis Pygmy rock crab

I found this crab upside down on the sand below a mussel-laden rock during a pretty low tide. The crows had been working the area pretty hard, so it’s possible they dislodged it before I arrived. Whatever the circumstances, it didn’t seem to be injured, and I didn’t resist the urge to flip it over for a right-side-up look.

Upside-down Glebocarcinus oregonensis pygmy rock crab on sand.
As I found it
A disturbed Glebocarcinus oregonensis pygmy rock crab, pinching claws up, on the sand.
Seven seconds later


Glebocarcinus oregonensis highlights

Closeup of a hand-held Glebocarcinus oregonensis pygmy rock crab curled up in its defensive posture.
The renowned defensive posture
Closeup dorsal view of Glebocarcinus oregonensis pygmy rock crab in a finger bowl, illustrating hairiness and the shape of the carapace viewed from above.
Hairy on the edges and an almost circular carapace outline


This crab was out on the sand in an area where several rocks jut from the sand. I have a feeling the birds disturbed it, but, as in the previous example, I can’t be sure. Nevertheless, when small crabs like Glebocarcinus are exposed on open sand during daylight hours they are pretty vulnerable.

Closeup of a mostly sand-covered Glebocarcinus oregonensis pygmy rock crab on the sand.


Posed on what I hope is its home rock and washed free of sand, you can see its hairy legs and impressive claws.

Closeup of a Glebocarcinus oregonensis pygmy rock crab posed on a sandy seaweed-covered rock.
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Cancer productus Red rock crab

On the sandy beaches of the open coast, I don’t cross paths with a ton of red rock crabs, but when I do–usually in places where there are at least a few rocks—there’s a good chance they’ve already been discovered by sport harvesters more interested in Dungeness crabs.

Head on closeup of a disturbed red rock crab Cancer productus in the swash, claws up in a combative stance.


When I found the crab below, it was already disturbed, so I went ahead and flipped it over for a look at its underside. I believe the narrow shape of its abdomen confirms this example is a male. (The abdomen of a female would probably be comparatively a bit broader and more rounded than what you see in the right-hand panel.) Another thing to notice on the right-hand panel is the underside can have some color, but it isn’t really spotted. (For comparison see Romaleon antennarium below.)

Closeup on a red rock crab Cancer productus partially buried in swash zone sand.


The fabled pinching claw

Closeup of one red rock crab Cancer productus pinching claw on a bed of Ulva.
Orcas Island


The color and pattern differences between juveniles and adults can be kind of surprising if you’re not ready for them. Juveniles are variable but their color is usually lighter than adults; it and the pattern change over the course of development.

Small juvenile red rock crab Cancer productus resting on a sand, gravel, and shell substrate.
Central Oregon


A drifted carapace

Closeup of an empty and drifted red rock crab Cancer productus carapace resting on the sand.
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Romaleon antennarium Spot-bellied or Pacific rock crab

A nearly head-on view of a spot-bellied or Pacific rock crab Romaleon antennarium tucked in under a large Pisaster, on sand at the base of a boulder.
A nearly head-on view of the outline of a spot-bellied or Pacific rock crab Romaleon antennarium completely buried in sand at the base of a boulder.
A close up view from above of a spot-bellied or Pacific rock crab Romaleon antennarium with a clean shiny shell resting on a bed of seaweed.
Central Oregon
Closeup of a spot-bellied or Pacific rock crab Romaleon antennarium in a shallow sand-filled pool. The crab's shell is somewhat encrusted with barnacles.
Closeup on a spot-bellied or Pacific rock crab Romaleon antennarium partially buried iat the sand/rock interface in a shallow sand-filled pool.
Central Oregon


I flipped over these individuals to reveal the namesake belly. The upper right-hand panel shows the narrow abdomen of the male and the bottom panel shows the broader abdomen of the female.

Closeup on the anterior underside of a spot-bellied or Pacific rock crab Romaleon antennarium. Sand in the background.
Closeup of the anterior underside of a spot-bellied or Pacific rock crab Romaleon antennarium. The narrow abdomen of a male is visible. Sand in the background.
Central Oregon
Closeup of the anterior underside of a spot-bellied or Pacific rock crab Romaleon antennarium. The broad abdomen of a female is visible. Seaweed in the background.


Juvenile spot-bellies have plenty of similarities to adults but one obvious difference is the juveniles are hairier; they have a hairy carapace and their legs seem hairier too.

Closeup showing the underside of a hand-held juvenile spot-bellied or Pacific rock crab Romaleon antennarium. Sand in the background.
Closeup showing the carapace and legs of a hand-held juvenile spot-bellied or Pacific rock crab Romaleon antennarium. In a small glass bowl. Sandy background.


Spot-belly molts and drifted remains are occasional beach combing finds on the beaches I visit most, but not nearly to the degree seen in the Dungeness crab (see next entry).

Closeup of the underside of a drifted spot-bellied or Pacific rock crab Romaleon antennarium molt resting on the sand. One pinching claw and the abdomen are missing.
Central Oregon
Closeup of part of an empty and drifted molted pinching claw from a spot-bellied or Pacific rock crab Romaleon antennarium molt resting on the sand.
A fragment of an empty and drifted spot-bellied or Pacific rock crab Romaleon antennarium carapace resting upside down on the sand.
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Metacarcinus magister Dungeness crab

Dungeness crab Metacarcinus magister in a shallow sand-filled pool.
Dungeness crab Metacarcinus magister in a shallow sand-filled pool.
Dungeness crab Metacarcinus magister in a shallow sand-filled pool.


Compare the broad abdomen of the female (left-hand panel) with the narrower abdomen of the male (right-hand panel).

Closeup of the underside of a female Dungeness crab Metacarcinus magister. Sand in the background.
Closeup of the underside of a male Dungeness crab Metacarcinus magister. Sand in the background.


A beachcast babe, only about 3 cm across.

A closeup view from above of the dorsal surface of a juvenile Dungeness crab Metacarcinus magister resting on the sand.
A closeup head-on view of a juvenile Dungeness crab Metacarcinus magister resting on the sand.


Molts are seasonal, but stray carapaces and pinching claws are abundant year-round on just about any beach.

Closeup of a Dungeness crab Metacarcinus magister pinching claw on the sand. Scattered clumps of drifted eelgrass in the background.
Closeup of a drifted Dungeness crab Metacarcinus magister carapace resting on the sand. A few barnacles adorn the carapace.
Closeup of a Dungeness crab Metacarcinus magister pinching claw on the sand. Scattered clumps of drifted eelgrass in the background.
Closeup of a molted Dungeness crab Metacarcinus magister main body and legs, drifted and resting on wet sand.
Closeup of a drifted Dungeness crab Metacarcinus magister carapace resting on the sand with drifted green seaweed and a white feather.
Closeup of a molted Dungeness crab Metacarcinus magister main body and legs, drifted and resting on wet sand. Sans carapace.
Upside-down Dungeness crab Metacarcinus magister carapace, its bottom partially filled with wet sand.
A Dungeness crab Metacarcinus magister carapace and claws lie next to each other on the sand next to bird tracks.


Some beaches become so littered with shells during full-swing molts it can look like a die-off.

Sand littered with freshly molted Dungeness crab Metacarcinus magister shells, mostly walking legs.
Sand littered with freshly molted Dungeness crab Metacarcinus magister shells, mostly walking legs.


There are occasional intact molts that help you imagine the crab stepping out and leaving the old shell behind.

An intact Dungeness crab Metacarcinus magister exoskeleton with the carapace flipped over the top, on wet beach sand.
An intact Dungeness crab Metacarcinus magister exoskeleton with the carapace flipped over the top, on wet beach sand. Headland in the background. Beyond, a pink morning glow on the horizon.
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Pugettia producta northern kelp crab

Dorsal view, northern kelp crab Pugettia producta, on the sand at the base of a boulder.
Northern kelp crab Pugettia producta, on the sand and surfgrass.
Central Oregon
Northern kelp crab Pugettia producta peeking out from beneath the kelp.
Central Oregon


Compare the broad abdomen of the female (left-hand panel) with the narrower abdomen of the male (right-hand panel).

The underside of a female northern kelp crab Pugettia producta on swash zone sand.
The underside of a male northern kelp crab Pugettia producta on rain dimpled sand.


Avian scavengers won’t turn down a kelp crab.

A northern kelp crab Pugettia producta on the sand surrounded by bird tracks.
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Pugettia gracilis graceful kelp crab

The signature claw

The robust pinching claws of a graceful kelp crab Pugettia gracilis are prominent in a hand-held male. Seaweed and sand in the background.


Graceful kelp crabs look out of place on open sand, and indeed they are. When I see it, I feel like they’ve been chivvied by birds taking advantage of a low tide to hunt rarely exposed seaweed-covered rocks. The crab featured below is sparsely decorated, as graceful kelp crabs tend to be, but it sports good seaweed diversity.

A graceful kelp crab Pugettia gracilis looking somewhat exposed on smooth beach sand.
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Porcelain crabs

If I’ve correctly identified them, the set below compares Petrolisthes eriomerus (top left-hand panel), Petrolisthes cinctipes (top right-hand panel), and Pachycheles rudis (bottom panel). I confess I found the P. eriomerus example under a rock (violating my usual practice of not turning rocks) and moved it onto a patch of adjacent Ulva for a photograph. The other two were photographed as I found them—P. cinctipes out on the sand beneath a mussel-bearing rock, and Pachycheles rudis nestled on the top of a rock where it blended in wonderfully.

Petrolisthes eriomerus on a bed of Ulva.
Petrolisthes eriomerus | Orcas Island
Petrolisthes cinctipes looking a bit out of place on a bed of sand.
Petrolisthes cinctipes
Pachycheles rudis nestled on the top of a low intertidal rock along with snails, an anemone, and a sac-like brown seaweed.
Pachycheles rudis
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Oedignathus inermis Granular claw crab

In the regular view, that is, the view of undisturbed individuals, all you usually get to see is the larger of the two pinching claws, which makes it easy to understand this crab’s common name.

A large pinching claw blocks the entrance of a crevice inhabited by one or more granular claw crabs Oedignathus inermis. Red seaweeds and giant green anemones share the scene.
A large pinching claw blocks the entrance to a giant barnacle inhabited by one or more granular claw crabs Oedignathus inermis.


Despite their secretive nature, granular claw crabs seem awfully vulnerable when tides permit avian predators to hunt the low rocks.

You might find discarded remains that look like a whole body, or a claw or other body parts; what you won’t find is the abdomen. That’s the part the birds favor and they won’t willingly leave it behind.

Closeup on the drifted carcass of a granular claw crab Oedignathus inermis rests partially buried in the sand.
A detached and drifted claw from a granular claw crab Oedignathus inermis rests on the sand.
A detached and drifted claw from a granular claw crab Oedignathus inermis rests on the sand.
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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

Friends of Netarts Bay WEBS Crustaceans page. Accessed August 5, 2023.

It’s worth scrolling down to crabs in Common Sea Life of Southeastern Alaska: A field guide by Aaron Baldwin & Paul Norwood. Accessed August 5, 2023.


Species Accounts

Cowles, D. (2007). Romaleon antennarium (Stimpson), Schweitzer and Feldmann, 2000. Invertebrates of the Salish Sea. Rosario Beach Marine Laboratory. Accessed August 5, 2025.

Cowles, D. (2007). Oedignathus inermis (Stimpson, 1860). Invertebrates of the Salish Sea. Rosario Beach Marine Laboratory. Accessed August 5, 2025.

Cowles, D. (2005). Cancer productus Randall, 1839. Invertebrates of the Salish Sea. Rosario Beach Marine Laboratory. Accessed August 5, 2025.

Cowles, D. (2005). Glebocarcinus oregonensis (Dana), Schweitzer and Feldmann, 2000). Invertebrates of the Salish Sea. Rosario Beach Marine Laboratory. Accessed August 5, 2025.

Cowles, D. (2005). Hemigrapsus nudus (Dana, 1851). Invertebrates of the Salish Sea. Rosario Beach Marine Laboratory. Accessed August 5, 2025.

Cowles, D. (2005). Pachygrapsus crassipes Randall, 1839. Invertebrates of the Salish Sea. Rosario Beach Marine Laboratory. Accessed August 5, 2025.

Cowles, D. (2005 as edited). Pugettia gracilis Dana, 1851. Invertebrates of the Salish Sea. Rosario Beach Marine Laboratory. Accessed August 5, 2025.

Cowles, D. (2005). Pugettia producta (Randall, 1839). Invertebrates of the Salish Sea. Rosario Beach Marine Laboratory. Accessed August 5, 2025.

Cowles, D. (2005). Petrolisthes eriomerus Stimpson, 1871. Invertebrates of the Salish Sea. Rosario Beach Marine Laboratory. Accessed August 5, 2025.

Cowles, D. (2005). Pachycheles rudis Stimpson, 1860. Invertebrates of the Salish Sea. Rosario Beach Marine Laboratory. Accessed August 5, 2025.

Cowles, D. (2006). Petrolisthes cinctipes (Randall, 1839). Invertebrates of the Salish Sea. Rosario Beach Marine Laboratory. Accessed August 5, 2025.

Hiebert, T.C. 2015. Cancer antennarius. In: Oregon Estuarine Invertebrates: Rudys’ Illustrated Guide to Common Species, 3rd ed. T.C. Hiebert, B.A. Butler and A.L. Shanks (eds.). University of Oregon Libraries and Oregon Institute of Marine Biology, Charleston, OR. Accessed August 5, 2025.

Hiebert, T.C. and A. Burgess. 2015. Pugettia producta. In: Oregon Estuarine Invertebrates: Rudys’ Illustrated Guide to Common Species, 3rd ed. T.C. Hiebert, B.A. Butler and A.L. Shanks (eds.). University of Oregon Libraries and Oregon Institute of Marine Biology, Charleston, OR. Accessed August 5, 2025.

Maxwell, J. (2002 as edited). Metacarcinus magister  (Dana, 1852) Schweitzer and Feldmann, 2000. Invertebrates of the Salish Sea. Rosario Beach Marine Laboratory. Accessed August 5, 2025.


I updated this page on August 5, 2025.