2009 44c Kelp Forest: Northern Kelp Crab

Kelp Forest – Northern Kelp Crab
Nature of America

Issue Date: October 1, 2009
City: Monterey, CA

The northern kelp crab clings to a blade of giant kelp with her long, spindly legs.  Covered with spines, she is able to hold on to seaweed during the roughest of storms.  The crab has been feeding on kelp and algae throughout the summer, but fall has arrived and it is time for her to move to deeper waters to mate.

Out in the deep ocean, the young female chooses a mate.  The male passes a pocket of sperm to the female, which she can store for up to a year before  fertilizing her eggs.  She is also shedding her outer shell, and the male will stay with her and protect her until the new one hardens.

Winter is approaching, and the kelp is dying.  With no vegetation to eat, the northern kelp crab will feed on small sea creatures.  Hunting at night, she uses her speed to catch prey.

Hunting for food takes the kelp crab away from the safety of the kelp forest.  Unlike other crabs, she does not camouflage herself with debris.  Instead, she displays her red abdomen and her fearsome claws to scare off would-be attackers.  But even that won’t protect her from large fish and sea otters.

When spring comes again, the northern kelp crab will move back to the underwater forest, where she will again feed on kelp and algae.