Crab, spider
Maia brachydactylus
Method of production — Caught at sea
Capture method — Pot or creel
Capture area — North East Atlantic (FAO 27)
Stock area — Cornwall
Stock detail — 7e, 7f, 7g, 7h
Sustainability rating
info
Biology
Spider crabs are generally only to be found on southern and western coasts of the UK, although there are increasing reports of commercial quantities of spider crabs occuring in Wales, Ireland and the Isle of Man. It is the largest crab found in British waters, with a carapace width of up to 20 cm and a leg span of 50 cm or more. Spider crabs inhabit coarse sand mixed grounds and open bedrock from the shallow sublittoral zone to a depth of 120 m, although highest densities occur between 0 and 70 m. Large migrations of spider crabs occur during the early spring when they move into shallower water to spawn. Female crabs become berried (egg-bearing) from April onwards, and by June all mature females are berried. Hatching occurs from July until November, following which the crabs migrate back to deeper water. It has a juvenile phase of up to three years, which is spent in shallow water close to the coast, with a predominance of small male spider crabs on rockier areas. A number of moults take place resulting in increases in size of up to 33% per moult, with males generally having the greatest increases in size. Males have an additional moult to the females, during which their chelipeds (claw bearing legs) reach their final size relative to the body. After the final, or terminal, moult occurs, M. squinado becomes fully mature and enters the adult phase of its life cycle when it starts breeding. After this terminal moult, the spider crab will not grow any larger, unlike edible crabs which will continue to grow throughout most of their life. This makes ageing of spider crabs very problematic, as individuals of the same age may be of different sizes. Carapace widths for mature adults are from 8.5 -20 cm for males and 7-17.5 cm for females. Spider crabs are known to congregate in large numbers and form mounds.
Stock information
Criterion score: 0.5
info
Stock Area
Cornwall
Stock information
Management
Criterion score: 0.75
info
Capture Information
Criterion score: 0
info
Alternatives
Based on method of production, fish type, and consumer rating:
only fish rated 2 and below are included as an alternative in
the list below. Click on a name to show the sustainable options
available.
Abalone
Clam, Manila (Farmed)
Crab, brown or edible
Limpet, Slipper
Lobster, European
Lobster, Norway, Langoustine, Dublin Bay prawn or scampi
Mussel, mussels (Farmed)
Oyster, Native, oysters (Caught at sea)
Oyster, Native, oysters (Farmed)
Oyster, Pacific, oysters (Caught at sea)
Oyster, Pacific, oysters (Farmed)
Prawn, King (whiteleg), prawns
Prawn, Northern prawns, Northern shrimp
Prawn, Tiger prawns (Farmed)
Scallop, King, scallops
Scallop, Queen, scallops
Squid, Japanese flying
This system has been developed by the Marine Conservation Society to help consumers choose the most environmentally sustainable fish. For
full details, please see the full wild-capture methodology available here.
Stock or species status
| Score |
Descriptor |
| 0 |
Stock under fished and harvested within sustainable limits |
| 0.25 |
Stock fully fished and harvested within sustainable limits |
| 0.5 |
Stock level below sustainable level (BMSY) but harvested within sustainable limits |
| 0.75 |
Stock and fishing level or stock at increased risk |
| 1 |
Stock outside biological and/or safe fishing limits |
Management
| Score |
Descriptor |
| 0 |
Well-managed |
| 0.25 |
Management requires some improvement |
| 0.5 |
Partly effective management |
| 0.75 |
Poorly managed and requires considerable improvement |
| 1 |
No relevant or effective management measures in place |
Capture method and ecological effects
| Score |
Impact |
| 0 |
Very low impact |
| 0.25 |
Low impact |
| 0.5 |
Some or moderate impact |
| 0.75 |
High impact |
| 1 |
Very high impact or illegal |
Where environmental concerns from any one criteria are so great, a ‘critical fail’ may be triggered and the fishery awarded a default red
rating. For full details, please see the full wild-capture methodology available here.
The sustainability of fish can vary significantly depending on how and where it has been caught or farmed. Many single species are caught or farmed in a variety of ways and this range shows that, within a species, some sources may be more sustainable than others.
To find out specific ratings, click on the 'Show options for this fish' button under the image of the fish.
'Best choices' are rated 1 and 2 (green), 'Fish to Avoid' are rated 5 (red). Ratings 3 and 4 mean 'Think' (yellow and amber), as there are better rated alternatives.
Fish that are under review are shown with a question mark icon and no rating.
This system has been developed by the Marine Conservation Society to help consumers and businesses choose the most environmentally sustainable fish.
Seafood sources indicated as, 'To be assessed', are those that have not yet been assessed and assigned a rating or are undergoing a period
of review. These include sources previously rated by MCS for which the rating has lapsed, due to changes in the market or MCS priorities and
resources. Given that these sources are not fully assessed, the profile should not be used to infer the current sustainability of the
fishery or farmed species.
If you are interested in the sustainability of this seafood source, please let us know by emailing
ratings@mcsuk.org
Rating 1 (light green) is associated with the most
sustainably produced seafood.
Fish to Eat are rated 1 and 2, Fish to Avoid are rated 5.
Ratings 3 and 4 mean don’t eat too often.
This system has been developed by the Marine Conservation
Society to help consumers choose the most environmentally
sustainable fish.
Rating 2 (pale green) is still a good choice, although some
aspects of its production or management could be improved
Fish to Eat are rated 1 and 2, Fish to Avoid are rated 5.
Ratings 3 and 4 mean don’t eat too often.
This system has been developed by the Marine Conservation
Society to help consumers choose the most environmentally
sustainable fish.
Rating 3 (yellow) based on available information; these
species should probably not be considered sustainable at
this time. Areas requiring improvement in the current
production may be significant. Eat only occasionally and
check www.goodfishguide.org for specific details.
Fish to Eat are rated 1 and 2, Fish to Avoid are rated 5.
Ratings 3 and 4 mean don’t eat too often.
This system has been developed by the Marine Conservation
Society to help consumers choose the most environmentally
sustainable fish.
Rating 4 (orange) should not be considered sustainable, and
the fish is likely to have significant environmental issues
associated with its production. While it may be from a
deteriorating fishery, it may be one which has improved from
a 5 rating, and positive steps are being taken. However, MCS
would not usually recommend choosing this fish.
Fish to Eat are rated 1 and 2, Fish to Avoid are rated 5.
Ratings 3 and 4 mean don’t eat too often.
This system has been developed by the Marine Conservation
Society to help consumers choose the most environmentally
sustainable fish.
'Red improver' ratings are assigned to seafood sources which have been assessed and rated 5 (red) due to significant environmental concerns
with one or more aspects of their management, capture or production, yet credible efforts to improve these issues have been agreed through a
Fisheries or Aquaculture Improvement Project – a FIP or an AIP - and work is underway. Such projects are normally publicly listed at
www.fisheryprogress.org. MCS wants to encourage environmental improvements in fisheries and fish farms, and so does not recommend avoiding
these sources, as we normally do for seafood rated 5 (red rated).
'Best choice' fish are rated 1 and 2, Fish to Avoid are rated 5.
This system has been developed by the Marine Conservation Society to help businesses and consumers choose the most environmentally
sustainable fish.
Rating 5 (red) is associated with fish to be avoided on the
basis that all or most of the criteria for sustainablilty
have not been met.
Fish to Eat are rated 1 and 2, Fish to Avoid are rated 5.
Ratings 3 and 4 mean don’t eat too often.
This system has been developed by the Marine Conservation
Society to help consumers choose the most environmentally
sustainable fish.
Cornwall Good Seafood Guide
