Edible crab (Cancer pagurus)

Fishery

The edible crab is a decapod crustacean that is targeted using baited traps, a fishing gear often referred to as ‘pots’ or ‘creels’.  Landings (and effort) reflect the species ecology and migratory behaviour of females in particular, with peak landings occurring in September and October.
To participate in the Isle of Man fishery a vessel have a crab and lobster fishing licence. Each licence has a maximum pot limit of 500 pots, of which, no more than 300 can be set within the 0-3 nautical mile zone. Those pots within the 0-3 nautical mile zone must have escape gaps to allow juvenile and undersize animals to escape. The current minimum conservation reference size is 130 mm carapace width (CW), which is well above the size at functional maturity observed in the population. There is also a prohibition of ‘de-clawing’ edible crab at sea.

Life Cycle

The edible crab has an oval, reddish brown carapace with a distinctive “pie crust” edge and black tipped pincers. Adults can grow to 25 cm wide, weigh up to 3kg and live as long as 30 years. This species grows by a process of ecdysis, otherwise known as moulting.
As females approach the moulting season (typically August in Manx waters), male crabs will attend a female and guard her against predators and other competing males. After successful copulation, the female will begin a migration towards the brooding grounds. These migrations are thought to be against the prevailing tidal current, and can be 10s to 100s of kilometres in distance. The annual brood migration behaviour of females, which is around September and October in Manx waters, supports the autumn fishery when fishing vessels follow the female crab into deeper waters away from the coastline. These deeper waters are characterised by softer sediment, such as sand and mud, compared to the inshore mating grounds. Females seek out these sediments so that they can brood their eggs whilst partially recessed into the seabed.
Juveniles will typically stay in the intertidal zone until they reach 60-70 mm at which point they begin to cohabit the nearshore mating grounds, roughly 2-3 years before they reach sexual maturity themselves and recruit into the fishery.

Habitat & Distribution

Brown crabs are distributed around north-western Europe and are known to be abundant in British and Irish coastal waters. They can inhabit waters from the littoral zone to depths of over 100 m. Brown crabs utilise a variety of coastal habitats during different stages in their life history, from intertidal algae beds. to sandy and rocky seabeds and offshore muddy sands.