Crab reproduction

Mating and spawning of Dungeness crab occur at two different times. Mating occurs in the late spring and summer months when females are molting and males are still in a hard shelled condition. Pre-mating embraces of crab occur when males detect pheromones exuded by females indicating that they are ready to molt. At this time, male crab will carry females protecting them from other males.

Protecting their mate

When crabs are in a pre-mating embrace they are still capable of protecting themselves and their mate. Males can move their mate towards their back legs in a position like the one shown which allows use of their claws.

Pre-mating embrace times are synchronous among Dungeness crab, red rock crab go through the same process later in the year (late summer). This may partially explains why crabs may often be hard to attract to bait since they are eating less at this time.

Female crab molting

Unlike male and juvenile female crab, mature female crab (~3” carapace width and larger) most often molt under the protection of a male crab.

In the adjacent photo, the female can be seen beginning to molt (the old shell is beginning to be tipped forward and the “new” crab is exiting via the “splitting line”).

Males will juggle the female and protect her while in this vulnerable state.

Buried crab

During swift tidal exchanges, crab often bury themselves. This is why crabbing is best during the least amount of tidal exchange, or even better at slack tides.

Crab also bury themselves after a molt to allow their shell to harden enough to provide adequate protection.

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.

More about kelp crab