One lives in your tide pool. The other lives in the cold dark.

Rock crabs have a broad, hard shell ranging from reddish-brown to yellowish or olive, often marked with darker mottling. The edge of the shell is lined with blunt teeth, and their powerful claws are adapted for crushing hard-shelled prey.

They feed on mussels, clams, worms, small crustaceans, carrion, and whatever else the tide makes available. When the water falls, they retreat into cracks and beneath rocks where they stay protected from drying out.

Rock crabs are also important prey for larger animals, including fish, seals, and other predators, connecting the rocky shoreline with the wider Fundy food web.

Snow crabs live on sandy and muddy seafloors in cold marine waters. They are especially associated with temperatures below about 3°C and can occur at depths ranging from relatively shallow coastal water to several hundred metres.

Their long legs give them their distinctive spider-like appearance, while the claws provide the valuable meat that supports an important commercial fishery.

Adult male snow crabs eventually reach a terminal moult. After this final moult, their shell and body no longer increase in size. Females have a different growth and reproductive cycle.

European green crabs are an introduced species that can compete with native animals and disturb coastal habitats. They dig through sediment while feeding and can damage eelgrass beds and other shallow-water habitat.

If you see a small greenish or brown crab with five teeth or spines along the shell behind each eye, it may be a European green crab rather than a native rock crab.