Green Crab

• It is among the 100 most damaging invasive species in the world according to the IUCN.
• It reached North America as early as 1817, carried accidentally aboard ships.
• It can lay as many as 185,000 eggs at a time.
• It figures on the list of the world's hundred worst invasive species, and it is one of the most widespread marine invaders on the planet: native to the north-east Atlantic, today it is established in North America, Australia, South Africa, Japan, Argentina and Patagonia.
• It travels in ballast water and in hull fouling, and its planktonic larvae do the rest.
• Its impact is measurable: in New England it is blamed for the collapse of soft-shell clam fisheries, and in Canada it uproots eelgrass meadows as it digs.
• It tolerates an enormous range of conditions: it survives from 0 to 30 °C, in salinities from 4 to 54, and endures days out of the water.
• It is extraordinarily effective at opening bivalves: it applies its claw at the exact point where the shell is weakest, and it learns to do it better with experience.
• In its native European range it is a common and ecologically unremarkable species; the problem appears only where nothing keeps it in check.

Skeleton type

Invertebrate - calcified exoskeleton (crustacean)

Habitat & environment

A wide range of coastal and intertidal habitats of the north-eastern Atlantic, widely introduced to North America, Australia and South Africa

Birth weight

A tiny zoea larva on hatching, released into the plankton

Size at birth

A fast-growing planktonic zoea larva for 17-80 days depending on temperature

Sexual maturity

Under a year to 3 years depending on the region (faster in warm water)

Gestation / incubation

Several months of egg development under the female's abdomen through the winter

Litter / clutch size

Up to 100,000-185,000 eggs per clutch

Sources consulted: Oxford Academic (Journal of Crustacean Biology, Maine study); The Exotics Guide; Texas Invasive Species Institute; Vic High Marine; Animal Diversity Web; PMC (Southwestern Atlantic life-history study); MDPI (life history population dynamics review)