Portal:National Park Service

“ A large female crab can carry 2.5 million eggs. Egg incubation tends to be much longer in Alaska than further south. The female crab stores the sperm until her eggs are fully developed. In Alaska, fertilization typically occurs in September.
Many female crabs do not reproduce annually in Alaska. Larger females (greater than 141 mm in carapace width) are probably the group of females that do not reproduce annually, possibly because they don't molt as often and rely on stored sperm to fertilize their eggs. ”

“ These groups seem to suggest a selfish herd or schooling phenomenon in which individuals gain protection in numbers through greater watchfulness and confusion of predators. Another explanation for these groups can be found in the fact that in 3 recently observed male aggregates, the distance from the nearest known female assembly averaged 200 meters, a lot closer than would be expected to occur randomly. Juveniles live in intertidal and shallow subtidal areas, hiding underneath or among plants, rocks, shell debris and eelgrass beds. ”

“ When the female molts, she is ready to be mated with a male who protects her while mating. Mating occurs in the late spring or early summer. The eggs are not fertilized until the female extrudes them under her abdomen where they are carried for 3­5 months until hatching. ”

“ Juveniles also prefer cooler waters than adults. Adult crabs prefer eelgrass beds and sandy or muddy substrate. Breeding occurs in nearshore areas and females usually move to deeper water to hatch eggs. ”

“ Megalopae are relatively strong swimmers, moving at speeds up to 22 centimeters per second, and are typically present in surface waters only at dawn, dusk and night. During the day, they usually move down in the water column to a depth of at least 20 meters. ”

“ Instead crabs must regularly shed their exoskeletons in order to increase in size. This process is known as molting, and individuals typically increase in size by about 15 to 25 per cent with each molt. ”