Different types of crab

Crabs are generally covered with a thick exoskeleton, and armed with a single pair of chelae (claws). They are found in all of the world’s oceans, while many crabs live in fresh water and on land, particularly in tropical regions. Crabs vary in size from the pea crab, a few millimetres wide, to the Japanese spider crab, with a leg span of up to 4 metres.

But we are really interested in Cancer pagurus commonly known as the brown crab. It is found in the North Sea, North Atlantic Ocean. It is a robust crab of a reddish-brown colour, having an oval carapace with a characteristic “pie crust” edge and black tips to the claws. A mature adult may have a carapace width of up to 25 cm (10 in) and weigh up to 3 kg (6.6 lb).

The brown crab is a nocturnal predator, targeting a range of molluscs and crustaceans. It is the subject of the largest crab fishery in Western Europe, centred around the coasts of the British Isles, with more than 60,000 tonnes caught annually.

There is a distinction in flavour, richness, colour and texture between white and brown crab meat contained in the brown crab making them quite different from one another.

Brown crab meat is found in the shell cavity at the top of the crab. It has higher flavour content than white meat which makes its richness ideal for sauces. The texture is less appealing to most people resulting in a lower price than white crab meat. Brown meat has a higher natural fat content but is extremely high in Omega-3.

White meat is found in the claws, legs and main body section of the crab. It is low in fat and high in protein. White meat is moist, flaky, sweet and more delicate in flavour.

How to catch a crab

The brown crab (Cancer pagurus) can be caught along the shallow coastal waters of the UK. They live in crevices, under rocks or burrows, from which they emerge at slack water to feed on a wide range of organisms living on the sea-bed, including other shellfish, which they crush with their powerful claws.

Crabs are captured in pots that are either top opening (inkwell pot) or side opening (parlour pot). Pots are fished individually or in a string of up to 100 pots, at each end of which is an anchor and buoy. Pots are raised every couple of days to check the catch

Fishing with pots is considered a sustainable fishing method for two reasons. Firstly, there is a behavioural buffer against overexploitation, because capture relies on crabs and being attracted to the pot only when they are feeding. Secondly, fishing with pots has very little effect on the seabed or other organisms in the fishing area.

The brown crab (Cancer pagurus) can be caught along the shallow coastal waters of the UK. They live in crevices, under rocks or burrows, from which they emerge at slack water to feed on a wide range of organisms living on the sea-bed, including other shellfish, which they crush with their powerful claws.

Where to catch crab

The brown crab is abundant throughout the northeast Atlantic as far as Norway in the north and northern Africa in the south, on mixed coarse grounds, mud and sand from the shallows to depths of about 100 metres. It is frequently found inhabiting cracks and holes in rocks but occasionally also in open areas.

Off the coast of Salcombe is a particular sweet spot for catching the most flavoursome crabs. It is a heavily guarded secret amongst the local Fisherman but they put the great flavour down to the deep waters which force the crab to develop a thick shell and strong muscles, and the lime stone cliffs which are an excellent habitat for the crabs.

Adult crabs are nocturnal, hiding buried in the substrate during the day, but foraging at night up to 50 metres from their hideouts. Their diet includes a variety of crustaceans and it may stalk or ambush motile prey, and may dig large pits to reach buried molluscs. The main predator of the brown crab is the octopus, which will even attack them inside the crab pots that fishermen use to trap them.

Lifecycle of a crab

Reproduction occurs in winter when the male captures the female and holds her under himself until she moults. Internal fertilisation takes place before the hardening of the new carapace, with the aid of two abdominal appendages.

After mating, the female retreats to a pit on the sea floor to lay her eggs. Between 250,000 and 3,000,000 fertilised eggs are held under the female’s abdomen for up to eight months until they hatch.

The first developmental stage after hatching is a planktonic larva (1 mm) called the zoea that develops into a postlarva, and finally a juvenile. The first juvenile stage is characterised by a well-developed abdomen, which will, in time, become reduced in size and folded under the sternum.

Juveniles settle to the sea floor in the intertidal zone, where they stay until they reach a carapace width of 60–70 mm and then migrate to deeper water. The growth rate in males slows from an increase in carapace width of 10 mm per year before it is eight years old, to 2 mm per year thereafter.

Females grow at about half the rate of males, probably due to the energetic demands of egg laying. Sexual maturity is reached at a carapace width of 12.7 cm in females, and 11 cm in males.

Longevity is typically 25–30 years, although exceptional individuals may live for up to 100 years.

Sustainability of crab

We of course believe in ethical fishing and adhere to minimum landing sizes in the UK. By releasing back into the sea any crab that is too small or a berried female (with eggs), the crabs are allowed to grow to maturity to sustain breeding stocks.

Minimum landing sizes (MLS) for the brown crab are set by both the European Union technical regulations and by the UK government. Different minimum sizes are employed in different geographical areas, to reflect differences in the crab’s growth rate across its range.

Around Devon, Cornwall and the Isles of Scilly, there is a separate MLS for males (160 mm) and females (140 mm).

The catch of brown crab has increased steadily, rising from 26,000 tonnes in 1978 to 60,000 tonnes in 2007, of which more than 70% was caught around the British Isles. In 2010 the volume of crab landed in the UK by UK vessels was an incredible 28,800 tonnes.

Most of the edible crabs caught by the British fleet are exported live for sale in France and Spain.