Atlantic rock crab
Fish · Last reviewed 2026-08-25
The fast dark crab that runs across Macaronesian splash-zone rock — regulated quarry with a closed season, standard bait, and the animal a Madeiran survey and a Canary government table each named under a different binomial.
Safety: slips, trips and falls — can cause serious injury or death. One more point applies here.
Catching Atlantic rock crab
Everything here on fishing for it. Each entry opens the page behind it.
- Ground
- Where
- 6 places FishingHQ documents — strongest claim anywhere: established quarry · From the shore
*Grapsus adscensionis* (Osbeck, 1765) is the crab anybody who has stood on a Canary or Madeiran rock platform has watched: dark, flat, fast, running sideways across wet rock in the splash zone and dropping into the water when approached.
IT IS ONE ANIMAL AND NOT TWO, WHICH TAKES A TAXONOMIC CHECK TO ESTABLISH. The Madeiran shore-angling survey records `Grapsus webbi` in its catch table. The Canary fisheries directorate regulates `Grapsus adscensionis`. Two archipelagos, two binomials, and the natural reading is two species. The World Register of Marine Species records *Grapsus webbi* H. Milne Edwards, 1853 as a JUNIOR SUBJECTIVE SYNONYM of *Grapsus adscensionis* — the same crab, twice named.
Macaronesian fishing vocabulary sets this trap constantly in local names — caballa, cabrilla and chicharro each mean different fish in different islands. It is far rarer, and far more dangerous, in SCIENTIFIC names, because a binomial is the thing a reader trusts precisely so that they do not have to check.
IT IS BOTH QUARRY AND BAIT, which is why it is regulated. The Canary directorate sets a minimum size across the carapace and closes it, with the white crab *Plagusia depressa*, over the winter. The closure carries a stated exception for crabs used as bait, and a further specific one for recreational shellfishing on EL HIERRO — where two of the bait crabs may still be taken for bait alone during the closure, at a reduced quantity. That is one of only two places in the whole Canary table where a single island is named, which makes it an unusually specific statement about El Hierro's shore. The dates, the size and the quantity are the authority's; only the existence and shape of the provision is recorded here.
It is exceptionally hard to catch by hand: it faces the water, sees movement well, and has a long head start.
Where Atlantic rock crab is documented
Places where public sources describe this species as fished, with how it is fished and how strongly the evidence supports it. This is not a range map and it is not a recommendation — it is what has been written down about a fishery rather than a record of any individual catch, and being listed is never permission to fish.
Canary Islands
6 documented places
Gran Canaria
Island
Established quarry
From the shore
Fuerteventura
Island
Established quarry
From the shore
La Palma
Island
Established quarry
From the shore
La Gomera
Island
Established quarry
From the shore
El Hierro
Island
Established quarry
From the shore
La Graciosa
Island
Established quarry
From the shore
What these strengths mean
- Established quarry
- Fishing sources describe this as a normal local target here, not merely as caught.
Identification
No photograph of Atlantic rock crab has passed identity review yet, so none is shown. FishingHQ publishes a species photograph only once somebody has confirmed the animal in it against the species record’s own diagnostic features.
- Scientific name
- Grapsus adscensionis
- Family
- Grapsidae
- Water
- Saltwater
- Conservation status
- Not assessed
- Regions
- Western Europe, West Africa, North Africa
- A flattened, broad, squarish carapace built for running rather than for digging or swimming.
- Dark — near black in adults, with red, orange or yellow mottling that becomes more obvious in fresh or wet animals.
- Eyes set at the outer front corners of the carapace, giving a very wide field of view, which is the practical reason it is so hard to approach.
- Found in the SPLASH ZONE on wet rock above the waterline rather than in pools or under stones.
- The Canary directorate sets a minimum carapace size for it; the figure is the authority's to state.
- Grapsus webbi is the same animal: the World Register of Marine Species treats it as a junior subjective synonym of this species.
Size
- Typical
- 5–7 cm carapace width
- Large
- Over 8 cm
Exceptional: The minimum published by the Canary fisheries directorate sits inside the ordinary adult range, so a documented legal animal is an average adult rather than a large one.
Lifecycle and reproduction
Planktonic larval stages settle to the shore and the animal then lives out of the water for most of its life, returning to it to wet its gills and to escape. It grows by moulting and is long-lived for a shore crab.
Females carry eggs beneath the abdomen and release larvae into the water. The Canary winter closure is the period the directorate protects, and the reason a bait exception exists at all is that the same animal is the standard bait for the fish being caught around it.
Feeding and senses
An omnivore and scavenger, grazing algal film off splash-zone rock and taking anything dead or slow it finds. It works the band that is wetted by spray and wave rather than by tide.
Excellent wide-field vision from stalked eyes at the carapace corners, tuned to movement, together with vibration sensing through the rock. It watches an approaching person from a long way off and moves before there is any question of reaching it.
Through the year
Active year-round on the splash zone, more visible in warm sunlight and less so in heavy swell. The seasonal fact of consequence is the winter closure, with its stated bait exception and its El Hierro-specific provision.
Distribution
Eastern Atlantic islands and coasts: the Canaries, Madeira, the Azores, Cape Verde, Ascension and the adjacent west African shore, on splash-zone rock. Regulated as shore-gathering quarry across the Canary Islands and recorded, under its synonym Grapsus webbi, in a peer-reviewed Madeiran shore-angling catch table.
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
Standard Macaronesian shore bait and minor table quarry in one animal. The Madeiran survey records 72.3% of the archipelago's shore anglers using previously caught bait including crabs, and lists decapods among the natural baits used — so for most anglers this crab's significance is that it is caught on the way to fishing rather than fished for. Catching it is genuinely difficult and is usually done with a net on a pole or at night.
Handling and returning
Strong claws for its size and a determined pinch, though nothing that will do lasting damage to an adult hand. Hold it across the back of the carapace from behind, well clear of both claws — from in front there is no safe grip on a crab shaped like this one.
Safety
Slips, trips and falls — Can cause serious injury or death
This crab lives in the splash zone, so chasing it means going to the wettest, most weed-covered and most wave-exposed rock on the shore, moving fast, with attention entirely on the animal. That is the single most reliable way to be knocked off a Macaronesian platform.
What reduces it: Do not chase it. Anybody gathering this animal deliberately should be working from a stance chosen before the crab was seen, with the sea in view, and should let one go rather than follow it towards the water.
Injury while handling fish — Minor injury
The claws pinch hard and will hold on.
What reduces it: Take it from behind across the rear of the carapace, never from the front, and use a net rather than a hand where there is a choice.
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
Where to go next
Similar and related fish
Where it lives
More fish
Not related to this page — just the rest of the section. There is little else joined to this subject yet, and a short page should still lead somewhere.
Sources and evidence
- WoRMS — the World Register of Marine Species — WoRMS Editorial Board, hosted by the Flanders Marine Institute (VLIZ) (Scientific institute)Relied on for: The accepted name, naming authority, taxonomic status and family for Grapsus adscensionis, and the synonymy of Grapsus webbi with it.States this directlyPassage read and verified
- Tallas mínimas de captura — Canarias: minimum landing sizes and closed seasons — Gobierno de Canarias, Consejería de Agricultura, Ganadería y Pesca — Dirección General de Pesca, with the Grupo de Acción Costera de Tenerife and the Cabildo de Tenerife (Government fisheries body)Relied on for: That this animal is regulated recreational shore-gathering quarry in the Canary Islands, the Canarian common name the directorate gives it, and the existence and shape of the closed seasons it states.States this directlyPassage read and verified
- Importance of recreational shore angling in the archipelago of Madeira (northeast Atlantic) — Scientia Marina (CSIC), vol. 84 no. 4, 2020 (Scientific literature)Relied on for: That this animal is recorded in the recreational shore-angling catch of the Madeira archipelago, at 0.04%, recorded there as Grapsus webbi of the estimated total by the study's own catch-composition table.States this directlyPassage read and verified
- General angling website restatements of established technique — Various (Credible secondary source)Relied on for: The widely restated practitioner account of how this animal is gathered — the ground, the state of tide, and the tools used.Background and mechanism onlyCitation checked — the work exists and is described correctly
Why the 3 connections on this page are here, and the sources
Similar and related fish
Backed by research — 1 connection
Supported by peer-reviewed research or fisheries science. The sources are listed and can be checked.
Velvet swimming crab
Grapsus adscensionis is a grapsid built for running on dry splash-zone rock, with a flattened square carapace and wide-set eyes at its front corners. Necora puber is a portunid built for swimming, with paddle-shaped rear legs, living in and under water rather than above it. A north-west European reader who knows the velvet swimming crab as shore bait will find this animal in a completely different place on the same shore.
- WoRMS — the World Register of Marine Species — WoRMS Editorial Board, hosted by the Flanders Marine Institute (VLIZ) (Scientific institute)Relied on for: The accepted names, naming authorities, taxonomic status, synonymy and families that separate these animals from one another.States this directlyPassage read and verified
How it is caught
What experienced anglers do — 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.
Crab snaring
The Madeiran creel survey records decapods among the natural baits its shore anglers use and 72.3% of them using previously caught bait including crabs. The consistent practitioner account is that this crab is extremely difficult to take by hand in daylight, because it faces the water with wide-set eyes and moves before a person is within reach — so it is taken with a long-handled net, or after dark when it is far less alert.
- Importance of recreational shore angling in the archipelago of Madeira (northeast Atlantic) — Scientia Marina (CSIC), vol. 84 no. 4, 2020 (Scientific literature)Relied on for: That Madeiran shore anglers collect intertidal invertebrates alongside their fishing, which animals they collect, and their use of previously caught bait.States this directlyPassage read and verified
- General angling website restatements of established technique — Various (Credible secondary source)Relied on for: The widely restated practitioner account of how this animal is gathered and used.Background and mechanism onlyCitation checked — the work exists and is described correctly
Where it lives
Official guidance — 1 connection
Stated by a fisheries authority, scientific institute or recognised angling body. Authoritative, but summarising rather than demonstrating.
Rocky shores and reefs
A fast grapsid crab of eastern Atlantic island rock, living above the waterline in the band wetted by spray and wave rather than by the tide, and regulated as shore-gathering quarry across the Canary Islands. It returns to the water to wet its gills and to escape rather than to feed.
- Tallas mínimas de captura — Canarias: minimum landing sizes and closed seasons — Gobierno de Canarias, Consejería de Agricultura, Ganadería y Pesca — Dirección General de Pesca, with the Grupo de Acción Costera de Tenerife and the Cabildo de Tenerife (Government fisheries body)Relied on for: That this animal is regulated recreational shore-gathering quarry across the Canary Islands, and the Canarian name the directorate gives it.States this directlyPassage read and verified
How FishingHQ labels evidence is explained in the evidence policy.