White-clawed crayfish
Fish · Last reviewed 2026-08-17
Britain's only native crayfish, Endangered, and being erased from its own rivers by a larger American relative that carries a disease it cannot survive — which is the single most important thing about crayfish here, and the catalogue could not say it.
Safety
Biosecurity and disease transfer — Can cause serious injury or death
Crayfish plague spores survive in damp nets, boots, waders, mats, buckets and boat gear, and are carried between catchments by people. Arrival in a water holding native crayfish typically destroys the whole population, and the population does not recover because the young do not disperse.
What reduces it: Check, clean and dry all equipment between waters, every time. Remove mud and plant material, wash, and dry thoroughly. Never move crayfish, water or wet substrate between waters. Where kit cannot be dried between consecutive trips, use separate equipment.
Worse when:
- Moving between catchments on consecutive days with equipment that has not dried
- Waters known to hold native crayfish, where the consequence is total and permanent
Fish welfare — Can cause injury needing treatment
An Endangered protected native is easily damaged by handling, and identification between native and invasive is not always straightforward for somebody who has not seen both.
What reduces it: Do not handle or retain crayfish. Return an accidental capture to the water it came from at once. Report an apparently native population in an unrecorded water to the environmental regulator rather than publicising the location.
Worse when:
- Berried females over winter
- Newly moulted animals in summer, which are soft and defenceless
FishingHQ held the signal crayfish and not this one. A page about an invasive species is a page about what it invaded, and there was nothing there to point at.
THE ANIMAL. A small freshwater crustacean, usually eight to ten centimetres, olive-brown to greyish, with claws that are dull white or pale pink UNDERNEATH. That colour is the name and it is the identification, because the animal that has replaced it has claws that are red beneath with a distinctive turquoise-white patch at the hinge.
IT IS ENDANGERED. Assessed as Endangered on the IUCN Red List, in decline across its whole European range, and in Britain reduced to isolated populations — many of them in headwaters, in isolated stillwaters, and in places deliberately chosen because nothing can get to them.
WHAT IS KILLING IT IS NOT COMPETITION. The signal crayfish, introduced from North America for aquaculture in the 1970s, carries a water mould — Aphanomyces astaci, crayfish plague — to which it is largely resistant and to which the white-clawed crayfish is not. Plague reaching a native population typically destroys it entirely, in a season. Competition and burrow displacement matter too; the plague is the mechanism that makes the loss total.
AND THE PLAGUE TRAVELS ON WET KIT. Spores survive in damp nets, boots, waders and boat hulls, and move between catchments in the boot of a car. That is a fact about anglers rather than about crayfish, and it is the reason the biosecurity routine on this page is not a formality.
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
- Austropotamobius pallipes
- Family
- Astacidae
- Water
- Freshwater
- Conservation status
- Endangered
- Regions
- Britain & Ireland, Western Europe, Central & Eastern Europe, Mediterranean
- CLAW UNDERSIDES ARE DULL WHITE TO PALE PINK. Turn the animal over — the underside of the claws is the character. A signal crayfish's are red, with a conspicuous turquoise-white patch at the claw hinge on the upper surface.
- SMALLER. Usually 8–10 cm and rarely over 12. A signal crayfish commonly reaches 16 cm and can exceed that, so a very large British crayfish is not this species.
- ROUGHER, DULLER AND MORE OLIVE-BROWN, with a granular texture to the carapace. A signal crayfish is smoother and often more uniformly brown-red.
- TWO PAIRS OF POST-ORBITAL RIDGES behind the eyes, the second pair weak — a technical character used where the colour is ambiguous.
- THE ROSTRUM — the pointed projection between the eyes — is triangular with converging sides. Signal crayfish have a broader rostrum with more parallel sides.
- CONTEXT IS EVIDENCE. In most English and Welsh rivers, a crayfish seen is a signal crayfish. Native populations survive in scattered, often isolated waters, and a confident identification of a native matters enough to be worth checking properly.
Size
- Typical
- 8–10 cm total length.
- Large
- Over 11 cm is a large white-clawed crayfish.
Exceptional: Around 12 cm is the widely reported maximum. Any British crayfish substantially larger than that is almost certainly a signal crayfish.
Lifecycle and reproduction
Slow, and that is the whole conservation problem in one sentence. White-clawed crayfish mature at three to four years and live to around ten or twelve. Females carry a few tens to a couple of hundred eggs — a small number by aquatic standards — glued beneath the tail through winter, and release fully formed juveniles in late spring. There is no planktonic larval stage, so the young do not disperse: a population is genuinely local, recolonisation from downstream is slow or impossible, and a stretch of river cleared by plague stays cleared. Compare the signal crayfish, which matures faster, carries more eggs and grows larger, and the outcome of putting the two together is not in doubt.
Mating occurs in autumn. The female carries the eggs attached to the swimmerets beneath her abdomen through the winter — she is 'in berry' — and juveniles hatch and are released in late spring, having passed the vulnerable stage under their mother rather than in the water column. That is a low-fecundity, high-investment strategy suited to a stable habitat and very poorly suited to a novel disease. Because juveniles do not disperse in the plankton, every population is effectively isolated and any local extinction is permanent without deliberate translocation.
Feeding and senses
An omnivore and a detritivore. White-clawed crayfish take decaying plant material, invertebrates, small molluscs, carrion and occasionally fish eggs and fry, feeding mostly at night and sheltering by day under stones, in bank cavities and among tree roots. They are a significant processor of leaf litter in the streams they occupy, which is one reason their loss changes a watercourse rather than merely subtracting from it.
Chemoreception and touch dominate: long antennae and chemosensitive setae find food and detect other crayfish in darkness and turbid water. Vision is poor and largely for detecting movement and light level. They are strongly nocturnal, which is why a river can hold a population that a person walking its banks in daylight for years will never see.
Through the year
Active from spring through autumn and much less so in cold water. Females are in berry over winter. Moulting — necessary for growth and the period at which the animal is soft and defenceless — occurs mainly in summer. The seasonal pattern matters chiefly because survey work is done when the animals are active, and because a river's crayfish can appear absent at the wrong time of year.
Distribution
Western Europe, from Britain and Ireland through France, Iberia and Italy to the Balkans, in clean, well-oxygenated, generally calcareous streams, rivers and lakes with plenty of physical refuge. In Britain it is now largely confined to scattered and often isolated populations, with strongholds in northern England and parts of Wales, and it has been lost from much of its former range. The IUCN global assessment is Endangered. Ireland retains internationally significant populations and has, so far, no established signal crayfish.
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
It is not quarry, and that is the point of the record. The white-clawed crayfish is what makes the signal crayfish a story rather than a nuisance, it is why crayfish trapping in Britain occupies an unusual and strict regulatory position, and it is the reason the biosecurity routine that anglers are asked to follow exists at all. Anglers encounter it as an accidental capture, as a subject of survey and licensing where its presence changes what may be done in a water, and — most often — as the animal that used to be there.
Handling and returning
The honest answer is: leave it alone. This is a protected native in decline, its identification is not always obvious, and the most useful thing an angler can do for it is not to handle it and not to move anything wet between waters. If one is caught by accident, return it to the water it came from immediately and do not carry it anywhere. Never move crayfish between waters under any circumstances — that is how plague spreads and how populations end. Check, clean and dry nets, boots, waders, mats and boat gear between waters as a routine, because plague spores survive in damp equipment and the animal cannot survive their arrival.
Native or invasive: the check that takes five seconds
Britain has one native crayfish and several introduced ones, and the signal crayfish is the one that matters.
TURN IT OVER AND LOOK AT THE CLAWS. White-clawed crayfish have claw undersides that are dull white to pale pink. Signal crayfish have claw undersides that are RED, and — the character that names them — a conspicuous turquoise-white patch on the upper surface at the claw hinge, which was thought to resemble a railway signal.
THEN LOOK AT THE SIZE. A native rarely exceeds 12 cm. A signal commonly reaches 16 cm and larger. A big crayfish in an English river is not a native.
THEN THE TEXTURE AND THE ROSTRUM. The native is duller, browner, rougher and more granular, with a triangular rostrum whose sides converge. The signal is smoother, often redder-brown, with a broader rostrum.
AND THERE ARE OTHERS. Narrow-clawed, red swamp, spiny-cheek and virile crayfish have all been recorded in Britain. Anybody attempting a confident identification beyond native-versus-signal should be using a proper key, and anybody who thinks they have found a native population in a place with no records should tell the environmental regulator rather than the internet.
WHY THE DIRECTION OF ERROR MATTERS. Mistaking a signal for a native costs nothing but an unnecessary care. Mistaking a native for a signal, in a jurisdiction where one may be trapped and the other is protected, is a serious error — which is exactly why this page describes the identification and says nothing whatever about what may be done with either.
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.
Authoritative guidance
Stated by a fisheries authority, scientific institute or recognised angling body. Authoritative, but summarising rather than demonstrating.
- Environment Agency fisheries management, byelaws and rod licensing information — Environment Agency (Government fisheries body)Relied on for: Freshwater fisheries management in England: species status, invasive species policy and the framework under which freshwater organisms are managed.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 designations and the status of protected and priority species and habitats.States this directlyCitation checked — the work exists and is described correctly
- The IUCN Red List of Threatened Species — International Union for Conservation of Nature (Conservation authority)Relied on for: The global Red List category and the assessment behind it, assessed 28 January 2010. A statement about the species across its range and not about any managed stock.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
Crayfish plague, and why wet kit is the vector
The white-clawed crayfish is not being out-competed to death. It is being killed by a disease.
APHANOMYCES ASTACI IS A WATER MOULD. It is native to North America, where the crayfish evolved alongside it and are largely resistant — they carry it and are not destroyed by it. European crayfish have no such resistance. Arrival of the pathogen in a naive population typically means total mortality, often within a single season.
SIGNAL CRAYFISH BROUGHT IT. Introduced to Britain for aquaculture in the 1970s, they escaped, established, and carried the plague into catchments where it had never been. Competition and burrowing displacement matter as well — signals are larger, faster-growing and more aggressive, and their burrowing damages banks — but the plague is what makes the replacement complete rather than gradual.
AND THE SPORES DO NOT NEED A CRAYFISH TO TRAVEL. They survive in water and in damp material for a period, which means nets, keepnets, unhooking mats, waders, boots, buckets, boat hulls and any other wet kit can carry plague from one catchment to another in the back of a car. Catchments that no crayfish could reach on its own have been infected this way.
SO CHECK, CLEAN, DRY IS NOT A GESTURE. It is the specific control for this specific pathogen, and it is asked of anglers because anglers are among the few people who routinely move wet equipment between separate water bodies. Inspect and remove mud and debris, wash equipment, and dry it thoroughly — and where equipment cannot be dried between trips, treat that as the problem it is.
NEVER MOVE A CRAYFISH. Not to another water, not home, not to show somebody. It is both the most direct way to spread plague and, for the invasive species, a serious matter in law in most administrations.
WHAT THIS PAGE WILL NOT DO. It will not tell you whether crayfish may be trapped where you are, what licence is needed, what a trap may look like, or what must be done with what is caught. That position differs between administrations, has changed, and carries penalties. Ask the environmental regulator for the water concerned.
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.
Authoritative guidance
Stated by a fisheries authority, scientific institute or recognised angling body. Authoritative, but summarising rather than demonstrating.
- Environment Agency fisheries management, byelaws and rod licensing information — Environment Agency (Government fisheries body)Relied on for: Freshwater fisheries management in England: species status, invasive species policy and the framework under which freshwater organisms are managed.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 designations and the status of protected and priority species and habitats.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
- 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
Where it lives
- Lowland riversClean, well-oxygenated rivers with plenty of physical refuge — under stones, in bank cavities and among tree roots — are the classic habitat, and the physical refuge is not optional.
- Upland lakes and hill lochsSurviving British populations are disproportionately in headwaters and isolated waters, several of them chosen deliberately because the signal crayfish cannot reach them.
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.
Lowland rivers
A distributional and habitat claim about a protected native species, resting on the national conservation and fisheries literature.
- Environment Agency fisheries management, byelaws and rod licensing information — Environment Agency (Government fisheries body)Relied on for: Freshwater fisheries management in England: species status, distribution, invasive species policy and biosecurity practice.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 status of protected and priority freshwater species and habitats.States this directlyCitation checked — the work exists and is described correctly
Upland lakes and hill lochs
A distributional claim about a species whose remaining range is a conservation outcome rather than an ecological preference.
- Environment Agency fisheries management, byelaws and rod licensing information — Environment Agency (Government fisheries body)Relied on for: Freshwater fisheries management in England: species status, distribution, invasive species policy and biosecurity practice.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 status of protected and priority freshwater species and habitats.States this directlyCitation checked — the work exists and is described correctly
Understanding this fish
What these connections rest on (1)
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.
Freshwater crayfish as prey
An explainer that carries the mechanism the subject record depends on.
- Environment Agency fisheries management, byelaws and rod licensing information — Environment Agency (Government fisheries body)Relied on for: Freshwater fisheries management in England: species status, distribution, invasive species policy and biosecurity practice.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 status of protected and priority freshwater species and habitats.States this directlyCitation checked — the work exists and is described correctly
Told apart from
What these connections rest on (1)
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.
Signal crayfish
A comparison a reader with the animal or the decision in front of them actually needs, joining two records that resolve one another.
- Environment Agency fisheries management, byelaws and rod licensing information — Environment Agency (Government fisheries body)Relied on for: Freshwater fisheries management in England: species status, distribution, invasive species policy and biosecurity practice.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 status of protected and priority freshwater species and habitats.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.
Signal crayfish
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 Pacifastacus leniusculus 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 Pacifastacus leniusculus 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.
Protected species, and why some fish may not be taken
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
Environment and conservation
- Biosecurity: check, clean, dryCrayfish plague spores survive in damp nets, boots and mats and travel between catchments in the boot of a car. The biosecurity routine exists for this pathogen specifically.
- Invasive species and biosecurityThe clearest British case of an invasive species eliminating a native by disease rather than by competition, and the reason check-clean-dry is asked of anglers.
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.
Biosecurity: check, clean, dry
An environmental effect attached to the thing that causes it, resting on an authoritative source rather than on advocacy.
- Environment Agency fisheries management, byelaws and rod licensing information — Environment Agency (Government fisheries body)Relied on for: Freshwater fisheries management in England: species status, distribution, invasive species policy and biosecurity practice.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 status of protected and priority freshwater species and habitats.States this directlyCitation checked — the work exists and is described correctly
Invasive species and biosecurity
An environmental effect attached to the thing that causes it, resting on an authoritative source rather than on advocacy.
- Environment Agency fisheries management, byelaws and rod licensing information — Environment Agency (Government fisheries body)Relied on for: Freshwater fisheries management in England: species status, distribution, invasive species policy and biosecurity practice.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 status of protected and priority freshwater 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
- The IUCN Red List of Threatened Species — International Union for Conservation of Nature (Conservation authority)Relied on for: The global Red List category and the assessment behind it, assessed 28 January 2010. A statement about the species across its range and not about any managed stock.States this directlyCitation checked — the work exists and is described correctly
- Environment Agency fisheries management, byelaws and rod licensing information — Environment Agency (Government fisheries body)Relied on for: Freshwater fisheries management in England: species status, invasive species policy and the framework under which freshwater organisms are managed.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 designations and the status of protected and priority species and habitats.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
- 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
How FishingHQ labels evidence is explained in the evidence policy.