Spiny spider crab

Fish · Last reviewed 2026-08-17

A large, long-legged, orange-red crab that walks into British shallows in summer in numbers, is excellent eating, and is put back by most people who find one because they assume it is not worth having.

Safety

Injury while handling fish — Can cause injury needing treatment

The carapace and legs are covered in genuine spines that puncture a hand, and the claws pinch. Marine puncture wounds become infected readily. Picking the animal up by a leg detaches the leg.

What reduces it: Hold across the back of the carapace with the legs hanging, or use gloves. Wash and dress punctures properly and seek advice if a wound inflames.

Worse when:

Reaching blind into a gully or under a rock
Handling in a swell while snorkelling

Fish welfare — Can cause injury needing treatment

Decapod crustaceans are recognised as sentient in UK law following a formal review of the evidence. Boiling a live crab from cold water, or leaving one in a bucket in the sun, 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 by the recognised method and keep it cold. If it is not, put it back where it was found. Return berried females and soft newly moulted animals.

Worse when:

Warm days on the shore
Long gathering sessions with animals accumulating in a bag

In late spring and summer, spiny spider crabs move from deeper water into shallow inshore ground around the south and west of Britain and Ireland. Snorkellers find them in gullies, shore gatherers find them in pools, and divers find them piled on top of one another in mounds of dozens or hundreds.

IT IS NOT A SHORE CRAB AND IT IS NOT AN EDIBLE CRAB. A spider crab has a domed, pear-shaped, spiny carapace, long spindly legs that give it a span far greater than its body, two forward-pointing spines between the eyes, and a colour from orange-brown to brick red. It is usually covered in weed and sponge, which it deliberately attaches to itself.

IT IS ONE OF THE BEST CRABS IN EUROPE TO EAT and much of the British catch has historically been exported to countries that already knew that. There is less meat in it than in an edible crab of similar weight and the meat is sweeter.

AND IT IS THE THIRD BRITISH CRAB, WHICH IS WHY IT IS HERE. FishingHQ held the edible crab — the target of a pot — and the shore crab — the bait and the child's drop-net catch. The spider crab is the one a person actually meets by accident in summer, and the catalogue had nothing to say about it.

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: Maja brachydactyla
Family: Majidae
Water: Saltwater
Conservation status: Not assessed
Regions: Britain & Ireland, Western Europe, Mediterranean, North Africa, West Africa

LONG SPINDLY LEGS giving a span far greater than the body. An edible crab is broad and heavy-bodied with short thick legs; a spider crab looks like a different kind of animal entirely.
A DOMED, PEAR-SHAPED, SPINY CARAPACE, orange-brown to brick red, narrowing towards the front. The edible crab's carapace is a smooth broad oval with a pie-crust edge.
TWO FORWARD-POINTING SPINES BETWEEN THE EYES — the rostral spines. Diagnostic and easy to see.
OFTEN COVERED IN WEED, SPONGE AND HYDROIDS, which the crab attaches to hooked setae on its shell deliberately. A crab wearing a garden is a spider crab.
CLAWS ARE RELATIVELY SLENDER and much less powerful than an edible crab's crushing claws — the males' are longer than the females'.
IN SUMMER, IN SHALLOW WATER, IN NUMBERS. Mass inshore movement and moulting aggregations of dozens or hundreds are characteristic and nothing else in Britain does it.

Size

Typical: Carapace 12–17 cm long, with a leg span of 40–50 cm.
Large: Carapace over 18 cm, with a span approaching 70 cm.

Exceptional: Carapace around 20 cm is the widely reported maximum, in animals with a leg span comfortably exceeding half a metre.

Lifecycle and reproduction

Spider crabs have a terminal moult, which is unusual and important: growth stops permanently once the animal reaches maturity, so an adult spider crab never gets bigger and its shell ages, accumulating fouling organisms for the rest of its life. Juveniles moult repeatedly, and the moult to maturity is the last. Larvae are planktonic. The species undertakes real seasonal migrations — inshore in spring and summer to moult and breed in shallow warm water, offshore in autumn — travelling distances of tens of kilometres, which is remarkable for a walking crustacean and is documented by tagging.

Mating occurs immediately after the female's terminal moult, while she is soft, and males guard females through it — which is why the mass moulting aggregations matter. Females store sperm and may produce several broods from one mating, carrying eggs beneath the abdomen until they hatch into planktonic larvae. Because growth ceases at maturity, a large spider crab is an old spider crab rather than a fast-grown one, and the population's reproductive output depends on animals that cannot replace their shells if damaged.

Feeding and senses

An omnivore and a grazer. Spider crabs take algae, molluscs, echinoderms, worms and carrion, working slowly over ground with claws that pick rather than crush. Their impact on shellfish beds is real enough that they are regarded as a pest in some cultivation areas. They also decorate: setae on the carapace are used to attach weed, sponge and hydroids, which is camouflage that grows.

Chemoreception and touch dominate, as in most crustaceans, with stalked compound eyes giving good motion detection. The decorating behaviour implies a functional response to being visible, and the mass aggregations imply chemical communication between individuals, though the details are not well established.

Through the year

The seasonal movement is the defining behaviour. Spider crabs come inshore into shallow water from late spring, aggregate to moult and mate through early summer, and move back into deeper water in autumn. That is why they appear suddenly, in numbers, in places that had none a month earlier, and why they are almost entirely a summer encounter for anybody in shallow water.

Distribution

North-east Atlantic from the British Isles and Ireland south to West Africa, on rock, gravel, sand and mixed ground from the shallow subtidal to around a hundred metres. Common around the south and west of Britain and Ireland and scarcer to the north and east. The closely related Maja squinado occupies the Mediterranean, and older British literature uses that name for this animal.

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 do not recognise. Spider crabs are taken in pots, by hand while snorkelling or shore gathering, and occasionally on a baited line — and they are the crab a summer snorkeller in Cornwall, Pembrokeshire or west Cork is most likely to meet. There is an established commercial fishery, much of it historically for export. The catalogue's crab layer previously ran from bait to pot and missed the animal in between.

Handling and returning

The legs are long, spiny and easily broken, and the animal is much more fragile than its appearance suggests. Hold it across the back of the carapace with the legs hanging; do not pick it up by a leg, which will detach. The claws can pinch and are far less powerful than an edible crab's. If taken for the table, dispatch it properly and immediately rather than boiling it alive 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, not a cooking preference. Do not take berried females carrying eggs, and be aware that a recently moulted crab is soft, in poor condition and not worth taking.

WHAT MAY BE TAKEN, WHERE, WHEN AND HOW IS NOT ON THIS PAGE. Minimum sizes, licensing, closed areas, protected status and gathering restrictions differ between administrations and are revised. Check the current position with the fisheries or environmental authority for the water concerned.

The terminal moult, the summer mounds, and why a big spider crab is an old one

Two facts about this animal's growth explain almost everything a person will see it do.

GROWTH STOPS AT MATURITY. Spider crabs have a terminal moult: after the moult that brings them to maturity, they never shed again. The shell they are wearing is the one they will die in, which is why adult spider crabs accumulate weed, barnacles, sponge and hydroids until they are barely recognisable — and why a very heavily fouled animal is an old one.

SO SIZE IS NOT A GROWTH RATE, IT IS AN ENDPOINT. Every mature spider crab is at its final size. A large one did not grow faster; it was larger when it made its last moult.

AND THE LAST MOULT IS A SOCIAL EVENT. Spider crabs aggregate in shallow water in early summer, sometimes in mounds of dozens or hundreds piled on top of one another. The mounds appear to protect moulting animals — which are soft, defenceless and highly vulnerable — and mating takes place immediately after a female's final moult while she is still soft, with males guarding her through it.

DIVERS FIND THIS ASTONISHING AND IT IS EASY TO DISTURB. A moulting aggregation is the most vulnerable moment in the species' life cycle happening in shallow, accessible water. A soft, freshly moulted crab is also not worth taking: there is little meat and the animal is in poor condition.

THEY ALSO MIGRATE PROPERLY. Tagging has shown individuals covering tens of kilometres between inshore summer ground and deeper winter ground. A walking crustacean making a seasonal migration on that scale is not what most people assume a crab does.

Scientific evidence

Supported by peer-reviewed research or fisheries science. The sources are listed and can be checked.

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 eastern Atlantic and Mediterranean.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: shellfish and crustacean stock monitoring, biotoxin surveillance, distribution 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 here for the fishery context rather than for any statement of rules.States this directlyCitation checked — the work exists and is described correctly

Three British crabs, and which one you have

EDIBLE CRAB — broad, heavy, smooth reddish-brown carapace with a distinctive pie-crust edge, short thick legs, and massive black-tipped crushing claws. This is the crab a pot is set for and it is unmistakable once seen.

SHORE CRAB — small, green to reddish, squarish carapace with five points either side of the eyes, and everywhere on every British shore. This is the crab on a child's drop-net line and the source of peeler bait.

SPINY SPIDER CRAB — domed spiny pear-shaped carapace, two forward spines between the eyes, extremely long legs, and usually wearing weed. Summer, shallow, and in numbers.

AND A FOURTH WORTH KNOWING. The velvet swimming crab is smaller, with fine hair over the shell, brilliant RED EYES, and flattened paddle-shaped rear legs. It is the most aggressive crab on a British shore, it will not let go, and it is very good eating. It is not built in this catalogue yet and the shape audit records it as a named gap rather than an oversight.

WHY THE IDENTIFICATION MATTERS BEYOND CURIOSITY. Minimum sizes, permitted gear, berried-female rules and gathering restrictions all differ BY SPECIES as well as by place, so an identification is the first step in every question about what may be done — and FishingHQ answers none of those questions. It tells you what the animal is and points at the authority.

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.

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 eastern Atlantic and Mediterranean.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.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 here for the fishery context rather than for any statement of rules.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, gathering practice and regional convention, recorded as consensus rather than as scholarship.Background and mechanism onlyCitation checked — the work exists and is described correctly

Where to go next

How it is caught

What these connections rest on (2)

Practitioner consensus — 2 connections

Recreational potting
Practice, recorded as practice.
- Sea Angler — Bauer Media (Specialist angling publication)Relied on for: Contemporary UK sea angling and shore gathering practice as reported by practitioners: ground, seasonal timing, tackle, bait 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 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
Shore diving
Practice, recorded as practice.
- CMAS technical and sporting standards for underwater activities — Confédération Mondiale des Activités Subaquatiques (Standards body)Relied on for: Breath-hold diving and spearfishing practice, training structure and safety expectations as set out by the international underwater federation.States this directlyCitation checked — the work exists and is described correctly
- BlueWater Hunting and Freediving — BlueWater Freedivers, Ventura, California, 1995 (Practitioner report)Relied on for: Spearfishing practice: approach, quarry behaviour and the handling of speared fish, from a practitioner tradition distinct from the European one.States this directlyCitation checked — the work exists and is described correctly

Where it lives

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.

Inshore ground
A distributional claim about where a species is found, 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 eastern Atlantic and Mediterranean.States this directlyCitation checked — the work exists and is described correctly
Rocky shores and reefs
A distributional claim about where a species is found, 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 eastern Atlantic and Mediterranean.States this directlyCitation checked — the work exists and is described correctly

Understanding this fish

What these connections rest on (3)

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. Naming a particular species the catalogue happens to hold would invent a precision the evidence never had.
- 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 eastern Atlantic and Mediterranean.States this directlyCitation checked — the work exists and is described correctly

Practitioner consensus — 2 connections

Handling crabs and lobsters: alive, and then not
An explainer that carries the mechanism the subject 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, seasonal timing, tackle, bait 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 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
Taking crustaceans on breath-hold
An explainer that carries the mechanism the subject record depends on.
- CMAS technical and sporting standards for underwater activities — Confédération Mondiale des Activités Subaquatiques (Standards body)Relied on for: Breath-hold diving and spearfishing practice, training structure and safety expectations as set out by the international underwater federation.States this directlyCitation checked — the work exists and is described correctly
- BlueWater Hunting and Freediving — BlueWater Freedivers, Ventura, California, 1995 (Practitioner report)Relied on for: Spearfishing practice: approach, quarry behaviour and the handling of speared fish, from a practitioner tradition distinct from the European one.States this directlyCitation checked — the work exists and is described correctly

Told apart from

What these connections rest on (4)

Practitioner consensus — 4 connections

Edible crab
A comparison a reader with the animal or the decision in front of them actually needs, joining two records that resolve one another.
- 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 eastern Atlantic and Mediterranean.States this directlyCitation checked — the work exists and is described correctly
Mud crab
A comparison a reader with the animal or the decision in front of them actually needs, joining two records that resolve one another.
- 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, habitat association, shellfish and crustacean monitoring, and the biological basis of management advice.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: Habitat, 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
Shore crab
A comparison a reader with the animal or the decision in front of them actually needs, joining two records that resolve one another.
- 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 eastern Atlantic and Mediterranean.States this directlyCitation checked — the work exists and is described correctly
Velvet swimming 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 recorded because confusable species matter more to a reader than a shared family does, 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

Taking crabs, lobsters, squid and shellfish: how the rules are structuredMinimum sizes, berried-female provisions, pot limits and gathering restrictions differ by species and by administration.

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 representation in England, and the framework within which anglers are asked to check local rules.States this directlyCitation checked — the work exists and is described correctly
- JNCC species and habitat conservation advice — Joint Nature Conservation Committee (Conservation authority)Relied on for: UK conservation designation and the framework of protected species and habitats.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

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 eastern Atlantic and Mediterranean.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: shellfish and crustacean stock monitoring, biotoxin surveillance, distribution 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 here for the 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.States this directlyCitation checked — the work exists and is described correctly

How FishingHQ labels evidence is explained in the evidence policy.

Share this page