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Oregon Crab Species
Oregon Crab Species
Crab Identification

 

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Crab identification specifics

Green Crab | Kelp Crab | Rock Crab

 Green Crab

Carcinus maenas

Green crab, Carcinus maenas, can be a variety of colors. Most commonly they are greenish mixed with yellow, and often with reddish colored fleshy joints on their legs.

Green crab, in Oregon, typically inhabit shallow rocky areas of mildly salty waters, usually found in the mid to upper estuaries. They tend to be restricted to this area in large part, by the native red rock crab, Cancer productus, which is a critical competitor for the invasive green crab.

Green crab
Green crab

Trouble for young green crab

Much like the familiar Dungeness crab, young green crab will more often be found higher in estuaries than adults. This is generally a safer place for the more vulnerable small crab.

red rock crab lunch
red rock crab lunch

Tough livin’

When green crabs try to cohabitate with red rock crab, this is often the result. Adult green crab in the lower estuaries often get beaten up by the heartier and more aggressive native crab, such as Dungeness and red rock.

green crab belly
Clawless green crab

Identification

Click the photo on the right for a look at the key identifiers for green crab.

The 5 spines on each side and 3 bumps in the middle are the most common and easiest identifiers.

green crab ID
Green crab ID

I found a green crab! Now what?

Occasionally, clammers or crabbers will catch a green crab. Drop the crab off at an ODFW office, either live or frozen, with catch information (where and when caught).

ODFW shellfish staff works cooperatively with researchers tracking populations of the green crab. Biological information from recreational catches of this crab are important to aide the understanding of these populations.

green crab
I found a green crab

The crab on the right is NOT a green crab

Don’t get oversold on color for identifying crab. This is a juvenile Dungeness crab, which has just molted, the molt is the brown one in front and the live crab is the green one.

Beachgoers often see large numbers of these newly molted  and small “green” colored crab, which are in fact native Dungeness crab.

Dungeness juv
Dungeness crab

 Kelp Crab

Kelp Crab Climbers

Kelp crab are in the Majidae or “Spider crab” family. Several species in this diverse family are excellent climbers, many are found in the complex habitats of the Oregon’s rocky reefs.

Crab identification

kelp crab
Kelp crab

Vegetarian Crab?

Northern kelp crab, may look like intimidating predators, but they are actually primarily kelp eaters. They are very common in the lower estuary and the nearshore ocean, particularly within kelp beds and around structure such as pilings. Occasionally, kelp crab are caught by recreational crabbers, often just because they will climb on crab line.

kelp crab lunch
Kelp crab

Built for comfort

Unlike the sand dwelling Dungeness crab, kelp crab are designed for climbing. This is apparent when looking at their rear legs comparatively. The rear legs of a kelp crab are rounded and the dactyls (terminal segment of leg) feature a serrated edge easing climbing on kelp and other structure.

kelp crab leg
Kelp crab

Built for speed

The same feature of a Dungeness crab shows the flattened shape that enables them to travel across soft bottomed areas very quickly.

Dungeness leg
Dungeness crab

 Rock Crab

Red rock crab - Oregon’s native

Red rock crabs (Cancer productus) are native to Oregon. They are often called “Japanese Crab”; a misnomer that may cause worry among recreational crabbers.

Red rock crabs are in fact a native species found in the fossil record as well as in Native American middens.

They are an important component of Oregon estuaries and nearshore areas, and even function as a steward to the estuary by predating on invasive species such as green crab (Carcinus maenas).

Crab identification

Red rock crab
Red rock crab
Red rock crab habitat

As the name implies red rock crab prefer the harder substrate habitats such as rocks, pilings, and other structure.

Red rock crab prefer higher salinities than Dungeness crab and therefore are usually found in larger estuaries, close to the ocean. They are most common in Coos, Yaquina, and Tillamook.

Red rock crab pair
Red rock crab
juvenile red rock crab
Red rock crab juvenile

Colorful juveniles

As juveniles, red rock crab can be found in a wide variety of colors and patterns.

Juvenile red rock crab
Red rock crab juvenile
juvenile red rock crab
Red rock crab juvenile
juvenile red rock crab
Red rock crab juvenile

The last crab an invasive will meet

Red rock crab are significant predators on green crab. The two species rarely exist in the same habitats because of the aggressive nature of the native red rock and Dungeness.

Green crab in Oregon have likely been confined to a very limited habitat (shallow areas of upper estuary) because of the presence of red rock crab.

red and green
Red rock crab

Tidepool crabs

As a different method of crabbing, red rock crab can also be found in tidepools. Look for them near protective rock structure in the lower estuary and in nearshore areas.

tidepool crab
Red rock crab

A similar relative

The Pacific rock crab (Cancer antennarius) inhabits similar habitats as the red rock crab, however is more often found in the nearshore ocean.

Occasionally, these crab are caught in the bay.

They are easily discerned from red rock crab by their spotted undersides, brown/ purple color, and more haired legs. It’s species name “antennarius” is Latin meaning “antennae” this refers to the noticeable larger antennae of this species when compared to other cancer crabs.

pacific rock crab
Pacific rock crab

red rock vs pacific rock

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