Velvet swimming crab
Fish · Last reviewed 2026-08-17
The crab under every British rock that stands up and fights you — brilliant red eyes, a coat of fine hair, paddle back legs, and a grip that does not release. Excellent eating, exported in quantity, and ignored by almost everybody who meets one.
Safety
Injury while handling fish — Can cause injury needing treatment
A velvet swimming crab faces a threat rather than fleeing it, grips readily, and does not let go. The claws are sharper than an edible crab's despite being smaller, and the animal is frequently picked up from the front by somebody who has not met one before.
What reduces it: Hold across the back of the carapace between the rear legs where the claws cannot reach, or wear gloves. Do not reach blindly under rocks or into kelp. If one takes hold, put it back in the water rather than pulling it off.
Worse when:
- Reaching under rocks and into kelp holdfasts by feel
- Sorting a mixed catch out of a pot
- Working by torchlight on a night low tide
Fish welfare — Can cause injury needing treatment
Decapod crustaceans are recognised as sentient in UK law following a formal review of the evidence. Boiling from cold, and holding crabs submerged in a bucket of water where they suffocate, are both defensible only by habit.
What reduces it: Decide before collecting whether the animal is for the table. If it is, dispatch it properly and immediately and keep it cool, damp and shaded rather than submerged. Return berried females and soft newly moulted animals.
Worse when:
- Warm days on the shore
- Long gathering sessions with animals accumulating in a bag
Biosecurity and disease transfer — Minor injury
Rock turning on a low spring tide is how most shore gatherers find this animal, and a rock left upside down kills the community that was living underneath it.
What reduces it: Replace every rock the way it was, the same way up, in the same place. Do not move rocks that need two hands, because you will not put them back properly.
Worse when:
- Big spring tides, when the most productive ground is exposed and most people are on it
Turn over a rock on a British low tide and the crab that raises both claws and comes at you is this one.
IT IS NAMED FOR THE HAIR. A dense covering of fine short hairs over the shell gives it a matt, velvety look quite unlike the smooth polished carapace of a shore crab or the pie-crust edge of an edible crab. Underneath the hair the shell is brown with pale blue lines on the legs and claws.
THE EYES SETTLE IT INSTANTLY. Brilliant, unmistakable red. Nothing else on a British shore has them, and they are visible from further away than any other character on this record.
IT IS A SWIMMING CRAB. The rear pair of legs are flattened into paddles, and unlike an edible crab or a spider crab it can and does swim — usually sideways and fast, and usually away from you before you have decided what it is.
AND IT IS AGGRESSIVE IN A WAY THE OTHERS ARE NOT. Cornered, a velvet crab faces you, opens both claws and holds the position. It will grip and it does not let go quickly, which is the origin of every one of its local names — devil crab, witch crab, fighter crab.
IT IS ALSO VERY GOOD TO EAT and supports a substantial British and Irish fishery, most of it exported to Spain where the animal is prized. That combination — abundant, accessible, excellent, and thrown back by British gatherers who assume it is a nuisance — is why the shape audit recorded it as a named gap rather than a curiosity.
Identification
FishingHQ holds no photograph of this species whose identity and licensing it can vouch for, so it is not showing one. Misidentified fish photographs teach identification wrongly, and a picture with an unchecked caption would be worse than none. The identification points below are what to look at instead.
- Scientific name
- Necora puber
- Family
- Portunidae
- Water
- Saltwater
- Conservation status
- Not assessed
- Regions
- Britain & Ireland, Western Europe, Northern Europe, Mediterranean, North Africa
- BRILLIANT RED EYES. The fastest character on the animal and unique among British crabs — visible before anything else and diagnostic on its own.
- A DENSE COVERING OF FINE SHORT HAIRS over the carapace, giving a matt velvety appearance rather than the smooth or granular shell of the other British crabs.
- REAR LEGS FLATTENED INTO PADDLES. It is a swimming crab and it uses them; an edible crab and a spider crab cannot swim at all.
- PALE BLUE LINES on the legs and along the claw joints, over a brown shell.
- EIGHT TO TEN SHARP TEETH between the eyes at the front edge of the carapace — more, and sharper, than the shore crab's five broader points.
- SIZE 6–10 cm carapace width. Much smaller than an edible crab, similar to a large shore crab, and far more belligerent than either.
Size
- Typical
- 6–8 cm carapace width.
- Large
- Over 9 cm is a large velvet swimming crab.
Exceptional: Around 10 cm carapace width is the widely reported maximum.
Lifecycle and reproduction
A short-lived, fast-growing crab by comparison with the edible crab: maturity within two to three years and a life span of perhaps five or six. Females carry eggs beneath the abdomen through winter and release planktonic larvae in spring, which pass through several stages before settling to hard ground. Growth is by moulting throughout life rather than by a terminal moult, so a velvet crab keeps growing and keeps shedding — which means a soft newly moulted animal is a normal thing to find and is not worth taking.
Mating occurs immediately after a female's moult while she is soft, with males guarding females before and after — the pairs found under rocks in spring are exactly that. Berried females carry the egg mass through winter and release larvae in spring. Because the animal is comparatively short-lived and fast-growing, populations respond faster to fishing pressure than an edible crab's do, in both directions.
Feeding and senses
An active predator and scavenger, taking molluscs, small crustaceans, worms, algae and carrion, and hunting rather than merely foraging. The claws are cutters and crushers rather than the heavy pavement crushers of an edible crab, which suits a more varied diet. It feeds mostly at night and hides under rock, in kelp holdfasts and in crevices by day, which is exactly where a shore gatherer finds it.
Chemoreception and touch as in all crabs, with stalked compound eyes that are unusually conspicuous and give good motion detection. The aggressive display — facing a threat with both claws raised rather than retreating — implies it responds to being seen, and it is one of the few British invertebrates that will hold its ground against a person.
Through the year
Present year-round on rocky and mixed ground, moving into slightly deeper water in the coldest months and up into the intertidal in the warmer ones. Mating pairs are found under rocks in spring. Berried females are commonest through winter. The gathering and potting season follows the warmer months when the animals are shallow and in best condition.
Distribution
North-east Atlantic from Norway to Morocco and into the western Mediterranean, on rock, boulder, kelp and mixed ground from the low intertidal down to around seventy metres. Abundant around the whole of Britain and Ireland wherever there is hard ground.
This is a biological range — where the species occurs, not a prediction that you will catch one. To browse the fishing geography FishingHQ holds, start at fishing places.
Why anglers care
A genuine gathering and potting quarry that most British people meet and throw back. It is taken in pots alongside edible crab and lobster, by hand from under rocks on a low spring tide, and incidentally by anglers whose bait it steals. There is a substantial UK and Irish commercial fishery, most of the catch exported to Spain and France where the animal is valued far more highly than at home. Its place in this catalogue is as the third British crab a person actually encounters — after the shore crab and the edible crab — and the one nobody has told them about.
Handling and returning
It will grip and it will not let go, and the claws are sharper than an edible crab's even though they are smaller. Hold it across the back of the carapace between the rear legs, where the claws cannot reach, or use gloves; picking it up from the front is how people get held. A crab that has taken hold is usually best put back in the water rather than pulled off, which damages both parties.
If it is being taken for the table, dispatch it properly and immediately by the recognised method rather than boiling it from cold — decapod crustaceans are recognised as sentient in UK law following the review of the evidence, and the dispatch method is a welfare decision rather than a cooking preference. Keep it cool, damp and shaded rather than submerged in a bucket, which deoxygenates and kills it. Return berried females and soft newly moulted animals, and replace every rock you turn the way you found it — the community underneath a rock is what lives there.
WHAT MAY BE TAKEN, WHERE AND HOW IS NOT ON THIS PAGE. Minimum sizes, gathering restrictions, licensing, protected areas and permitted methods differ between administrations and are revised. Check the current position with the fisheries or environmental authority for the water concerned.
Four British crabs, and how to tell which is in front of you
The catalogue now holds four and they are separated in seconds once the characters are known.
EDIBLE CRAB — broad, heavy, smooth reddish-brown with a pie-crust edge to the shell, short thick legs, massive black-tipped crushing claws. The crab a pot is set for.
SHORE CRAB — small, green to reddish, squarish carapace with five broad points either side of the eyes, and everywhere on every British shore. The bait, and the child's drop-net catch.
SPINY SPIDER CRAB — domed spiny pear-shaped shell, two forward-pointing spines between the eyes, extremely long legs, usually wearing weed. Summer, shallow, and in numbers.
VELVET SWIMMING CRAB — red eyes, velvety hair, paddle back legs, blue lines on the claws, and an attitude. Under rocks and in kelp on hard ground.
THE SHORTCUT THAT WORKS EVERY TIME: look at the eyes. Red means velvet. Nothing else needs checking.
AND THE SECOND-FASTEST is the back legs. Flattened paddles mean a swimming crab; round-tipped walking legs mean everything else in Britain.
WHY THE IDENTIFICATION MATTERS BEYOND CURIOSITY. Minimum sizes, berried-female provisions and gathering restrictions apply BY SPECIES as well as by place, so knowing which crab is in your hand is the first step in every question about what may be done with it. FishingHQ answers none of those questions — it tells you what the animal is and names the authority.
WHAT MAY BE TAKEN, WHERE AND HOW IS NOT ON THIS PAGE. Minimum sizes, gathering restrictions, licensing, protected areas and permitted methods differ between administrations and are revised. Check the current position with the fisheries or environmental authority for the water concerned.
Practitioner consensus
Widely and independently recommended by experienced anglers and specialist sources. This is real angling knowledge, not proof: controlled evidence for it is limited, and FishingHQ records it as convention rather than as a demonstrated effect.
- The Fishes of the British Isles and North-West Europe — Macmillan, 1969 (Reference work)Relied on for: Distribution, habitat, identification characters and biology of the fishes and inshore fauna of the British Isles and north-west Europe.States this directlyCitation checked — the work exists and is described correctly
- FAO Species Identification Guides for Fishery Purposes and the FAO Species Catalogues — Food and Agriculture Organization of the United Nations (Scientific institute)Relied on for: Diagnostic identification characters, family placement, depth range and distribution as set out in the FAO species identification sheets for the region concerned.States this directlyCitation checked — the work exists and is described correctly
- Sea Angler — Bauer Media (Specialist angling publication)Relied on for: Contemporary UK sea angling and shore gathering practice as reported by practitioners: ground, tackle, seasonal timing and method convention.States this directlyCitation checked — the work exists and is described correctly
- General angling website restatements of established technique — Various (Credible secondary source)Relied on for: Widely restated descriptions of species behaviour, technique and regional practice, recorded as consensus rather than as scholarship.Background and mechanism onlyCitation checked — the work exists and is described correctly
The best crab nobody in Britain eats
There is a genuine oddity here worth stating plainly: an abundant, accessible, excellent shellfish that the country it lives in largely ignores.
THE FISHERY IS REAL AND IT IS AN EXPORT FISHERY. Velvet crabs are taken in pots around Britain and Ireland, particularly on the west coasts and in Scotland, and the great majority of the catch goes to Spain, Portugal and France, where the animal is a prized ingredient and commands a price that has made the fishery worth working.
AT HOME IT IS BARELY EATEN. The meat is sweet and there is proportionally less of it than in an edible crab, which requires more work per crab and is exactly the calculation a market makes and a cook does not. It is a picking crab rather than a dressing crab.
AND THAT MAKES IT AN UNUSUALLY GOOD GATHERING TARGET, where gathering is permitted. It is abundant, it is on ground a person can reach on a low tide, it is unmistakable, and taking a few is a smaller intervention than taking the same weight of edible crab — which is a slower-growing, longer-lived animal.
THE COUNTER-ARGUMENTS ARE REAL TOO. The fishery has grown substantially and stock assessment for velvet crab is less developed than for the edible crab or the lobster. Berried females are the reproductive output of the ground and should go back. And the ground itself — boulder and kelp on a low spring tide — is a community that suffers when every rock on it is turned and left upside down.
WHICH IS THE HONEST POSITION. Take a few where it is permitted, return berried and soft animals, put the rocks back, and understand that the reason this crab is unfamiliar is a market preference rather than anything about the animal.
Authoritative guidance
Stated by a fisheries authority, scientific institute or recognised angling body. Authoritative, but summarising rather than demonstrating.
- Good Fish Guide — Marine Conservation Society (Conservation authority)Relied on for: Assessment of the sustainability of UK-caught seafood by species, gear and stock, used for fishery context rather than for any statement of rules.States this directlyCitation checked — the work exists and is described correctly
- Cefas science, advice and data on marine and freshwater environments — Centre for Environment, Fisheries and Aquaculture Science (Government fisheries body)Relied on for: UK marine science: distribution, shellfish and crustacean monitoring, and the biological basis of management advice.States this directlyCitation checked — the work exists and is described correctly
- Sea Angler — Bauer Media (Specialist angling publication)Relied on for: Contemporary UK sea angling and shore gathering practice as reported by practitioners: ground, tackle, seasonal timing and method convention.States this directlyCitation checked — the work exists and is described correctly
Where to go next
How it is caught
- Gathering winkles, whelks and limpetsHand collection from under rocks on a low spring tide is how most people meet one, which is also why the rock-replacement point matters on this record.
- Recreational pottingTaken in pots alongside edible crab and lobster, and the object of a substantial UK and Irish commercial fishery, most of it exported.
What these connections rest on (2)
Practitioner consensus — 2 connections
Widely and independently recommended by experienced anglers and specialist sources. This is real angling knowledge, not proof: controlled evidence for it is limited, and FishingHQ records it as convention rather than as a demonstrated effect.
Gathering winkles, whelks and limpets
A statement about how a species is fished or collected, which is convention rather than biology and is labelled as such.
- Sea Angler — Bauer Media (Specialist angling publication)Relied on for: Contemporary UK sea angling and shore gathering practice as reported by practitioners: ground, tackle, presentation and seasonal timing.States this directlyCitation checked — the work exists and is described correctly
- General angling website restatements of established technique — Various (Credible secondary source)Relied on for: Widely restated descriptions of technique, quarry behaviour and regional practice, recorded as consensus rather than as scholarship.Background and mechanism onlyCitation checked — the work exists and is described correctly
Recreational potting
A statement about how a species is fished or collected, which is convention rather than biology and is labelled as such.
- Sea Angler — Bauer Media (Specialist angling publication)Relied on for: Contemporary UK sea angling and shore gathering practice as reported by practitioners: ground, tackle, presentation and seasonal timing.States this directlyCitation checked — the work exists and is described correctly
- General angling website restatements of established technique — Various (Credible secondary source)Relied on for: Widely restated descriptions of technique, quarry behaviour and regional practice, recorded as consensus rather than as scholarship.Background and mechanism onlyCitation checked — the work exists and is described correctly
Where it lives
- Kelp forestKelp and its holdfasts are prime velvet crab ground, and the animal is a significant predator within that community.
- Rocky shores and reefsUnder boulders, in kelp holdfasts and in crevices on hard ground from the low intertidal down — which is exactly where a shore gatherer on a low spring tide is looking.
What these connections rest on (2)
Scientific evidence — 2 connections
Supported by peer-reviewed research or fisheries science. The sources are listed and can be checked.
Kelp forest
A habitat association resting on the standard regional reference works rather than on angling report.
- The Fishes of the British Isles and North-West Europe — Macmillan, 1969 (Reference work)Relied on for: Distribution, habitat association, identification and biology of the fishes and inshore fauna of the British Isles and north-west Europe.States this directlyCitation checked — the work exists and is described correctly
- FAO Species Identification Guides for Fishery Purposes and the FAO Species Catalogues — Food and Agriculture Organization of the United Nations (Scientific institute)Relied on for: Diagnostic characters, family placement, habitat and depth range as set out in the FAO species identification sheets for the region concerned.States this directlyCitation checked — the work exists and is described correctly
Rocky shores and reefs
A habitat association resting on the standard regional reference works rather than on angling report.
- The Fishes of the British Isles and North-West Europe — Macmillan, 1969 (Reference work)Relied on for: Distribution, habitat association, identification and biology of the fishes and inshore fauna of the British Isles and north-west Europe.States this directlyCitation checked — the work exists and is described correctly
- FAO Species Identification Guides for Fishery Purposes and the FAO Species Catalogues — Food and Agriculture Organization of the United Nations (Scientific institute)Relied on for: Diagnostic characters, family placement, habitat and depth range as set out in the FAO species identification sheets for the region concerned.States this directlyCitation checked — the work exists and is described correctly
Understanding this fish
- Bivalve and gastropod molluscs as preyMolluscs taken from hard ground form a substantial part of the diet, described in the literature at group level.
- Handling crabs and lobsters: alive, and then notA crab that grips and does not release, with claws sharper than an edible crab's, plus the dispatch question that follows from decapods being recognised as sentient in UK law.
What these connections rest on (2)
Scientific evidence — 1 connection
Supported by peer-reviewed research or fisheries science. The sources are listed and can be checked.
Bivalve and gastropod molluscs as prey
A diet claim recorded at group level, pointed at a modelled prey CATEGORY, because the reference works describe the diet as a group rather than by species.
- The Fishes of the British Isles and North-West Europe — Macmillan, 1969 (Reference work)Relied on for: Distribution, habitat association, identification and biology of the fishes and inshore fauna of the British Isles and north-west Europe.States this directlyCitation checked — the work exists and is described correctly
- FAO Species Identification Guides for Fishery Purposes and the FAO Species Catalogues — Food and Agriculture Organization of the United Nations (Scientific institute)Relied on for: Diagnostic characters, family placement, habitat and depth range as set out in the FAO species identification sheets for the region concerned.States this directlyCitation checked — the work exists and is described correctly
Practitioner consensus — 1 connection
Widely and independently recommended by experienced anglers and specialist sources. This is real angling knowledge, not proof: controlled evidence for it is limited, and FishingHQ records it as convention rather than as a demonstrated effect.
Handling crabs and lobsters: alive, and then not
An explainer carrying a mechanism the record depends on.
- Sea Angler — Bauer Media (Specialist angling publication)Relied on for: Contemporary UK sea angling and shore gathering practice as reported by practitioners: ground, tackle, presentation and seasonal timing.States this directlyCitation checked — the work exists and is described correctly
- General angling website restatements of established technique — Various (Credible secondary source)Relied on for: Widely restated descriptions of technique, quarry behaviour and regional practice, recorded as consensus rather than as scholarship.Background and mechanism onlyCitation checked — the work exists and is described correctly
Told apart from
- Edible crabBoth are taken in pots and both are eaten, and they are different animals to handle: one has heavy black-tipped crushers and cannot swim, the other has sharper claws, swims, and will not let go.
- Shore crabThe two crabs under British rocks, and the fastest separation in the catalogue: red eyes and paddle back legs mean velvet, five broad points and no paddles mean shore crab.
- Spiny spider crabThe two British crabs most people throw back without knowing what they have. One is a summer arrival with legs that detach; the other is a year-round resident with an attitude.
What these connections rest on (3)
Practitioner consensus — 3 connections
Widely and independently recommended by experienced anglers and specialist sources. This is real angling knowledge, not proof: controlled evidence for it is limited, and FishingHQ records it as convention rather than as a demonstrated effect.
Edible crab
A comparison a reader with the animal or the decision in front of them genuinely needs.
- The Fishes of the British Isles and North-West Europe — Macmillan, 1969 (Reference work)Relied on for: Distribution, habitat association, identification and biology of the fishes and inshore fauna of the British Isles and north-west Europe.States this directlyCitation checked — the work exists and is described correctly
- FAO Species Identification Guides for Fishery Purposes and the FAO Species Catalogues — Food and Agriculture Organization of the United Nations (Scientific institute)Relied on for: Diagnostic characters, family placement, habitat and depth range as set out in the FAO species identification sheets for the region concerned.States this directlyCitation checked — the work exists and is described correctly
Shore crab
A comparison a reader with the animal or the decision in front of them genuinely needs.
- The Fishes of the British Isles and North-West Europe — Macmillan, 1969 (Reference work)Relied on for: Distribution, habitat association, identification and biology of the fishes and inshore fauna of the British Isles and north-west Europe.States this directlyCitation checked — the work exists and is described correctly
- FAO Species Identification Guides for Fishery Purposes and the FAO Species Catalogues — Food and Agriculture Organization of the United Nations (Scientific institute)Relied on for: Diagnostic characters, family placement, habitat and depth range as set out in the FAO species identification sheets for the region concerned.States this directlyCitation checked — the work exists and is described correctly
Spiny spider crab
A comparison a reader with the animal or the decision in front of them genuinely needs.
- The Fishes of the British Isles and North-West Europe — Macmillan, 1969 (Reference work)Relied on for: Distribution, habitat association, identification and biology of the fishes and inshore fauna of the British Isles and north-west Europe.States this directlyCitation checked — the work exists and is described correctly
- FAO Species Identification Guides for Fishery Purposes and the FAO Species Catalogues — Food and Agriculture Organization of the United Nations (Scientific institute)Relied on for: Diagnostic characters, family placement, habitat and depth range as set out in the FAO species identification sheets for the region concerned.States this directlyCitation checked — the work exists and is described correctly
Scientific evidence — 1 connection
Supported by peer-reviewed research or fisheries science. The sources are listed and can be checked.
Edible crab
Taxonomic and practical relatedness, with the evidence naming the species the edge is about.
- The Fishes of the British Isles and North-West Europe — Macmillan, 1969 (Reference work)Relied on for: Identification characters, family placement and biology of Cancer pagurus and of the species it is confused with, as set out for the fauna of the British Isles and north-west Europe.States this directlyCitation checked — the work exists and is described correctly
- FAO Species Identification Guides for Fishery Purposes and the FAO Species Catalogues — Food and Agriculture Organization of the United Nations (Scientific institute)Relied on for: Diagnostic characters and family placement of Cancer pagurus as set out in the FAO species identification sheets for the region concerned.States this directlyCitation checked — the work exists and is described correctly
Rules and access
What these connections rest on (1)
Authoritative guidance — 1 connection
Stated by a fisheries authority, scientific institute or recognised angling body. Authoritative, but summarising rather than demonstrating.
Taking crabs, lobsters, squid and shellfish: how the rules are structured
A link to a rule CONCEPT rather than to any rule. The record carrying it renders the regulatory-variance notice.
- Angling Trust guidance for anglers — Angling Trust (Angling or fisheries organisation)Relied on for: The structure of angling regulation and the framework within which anglers are asked to check local rules.States this directlyCitation checked — the work exists and is described correctly
- Cefas science, advice and data on marine and freshwater environments — Centre for Environment, Fisheries and Aquaculture Science (Government fisheries body)Relied on for: UK marine science underpinning shellfish and crustacean management advice.States this directlyCitation checked — the work exists and is described correctly
Check the rules before you fish
Fishing laws, bylaws, access rules, seasons, bait restrictions and permitted methods vary by location and can change. Check the current rules from the relevant authority and the water you intend to fish before fishing.
Check with:
- Current national or regional law for where you are fishing
- Current local bylaws
- The relevant fisheries authority
- The landowner, club or fishery whose water it is
- Any restrictions specific to the species or the method you intend to use
Sources for this page
- The Fishes of the British Isles and North-West Europe — Macmillan, 1969 (Reference work)Relied on for: Distribution, habitat, identification characters and biology of the fishes and inshore fauna of the British Isles and north-west Europe.States this directlyCitation checked — the work exists and is described correctly
- FAO Species Identification Guides for Fishery Purposes and the FAO Species Catalogues — Food and Agriculture Organization of the United Nations (Scientific institute)Relied on for: Diagnostic identification characters, family placement, depth range and distribution as set out in the FAO species identification sheets for the region concerned.States this directlyCitation checked — the work exists and is described correctly
- Cefas science, advice and data on marine and freshwater environments — Centre for Environment, Fisheries and Aquaculture Science (Government fisheries body)Relied on for: UK marine science: distribution, shellfish and crustacean monitoring, and the biological basis of management advice.States this directlyCitation checked — the work exists and is described correctly
- Good Fish Guide — Marine Conservation Society (Conservation authority)Relied on for: Assessment of the sustainability of UK-caught seafood by species, gear and stock, used for fishery context rather than for any statement of rules.States this directlyCitation checked — the work exists and is described correctly
- Sea Angler — Bauer Media (Specialist angling publication)Relied on for: Contemporary UK sea angling and shore gathering practice as reported by practitioners: ground, tackle, seasonal timing and method convention.States this directlyCitation checked — the work exists and is described correctly
How FishingHQ labels evidence is explained in the evidence policy.