Spider Crab

Maja brachydactylus

spider crab by Sarah McCartney

Image | Sarah McCartney Cornwall Wildlife Trust

Description

Spider crabs are large spiky creatures that are common around Cornwall’s coast. They grow up to 80cm in claw span. The claws are full of delicious moist, white meat that is a prized delicacy in Spain and France. They are harvested sustainably and are deicious and definately one that every visitor to Cornwall should try!
 

Sustainability Overview

Although spider crab stocks are little studied the methods used to catch them have minimal impact on the environment and the current level of fishing is unlikely to have a detrimental effect on the stocks. Minimum landing sizes and licences for shell fishing are set by Cornwall Inshore Fisheries and Conservation Authority (CIFCA) who monitor and regulate this fishery. This is an underutilzed species and the majority of the spider crab catch is exported to Spain. It would benefit small scale, sustainable fishermen if a better UK market for this species could be developed. 

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When is best to eat?

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Potting

Cornish waters

Pots are low impact and selective. Undersized catch can be returned safely and the pots don't damage the seabed.

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Gill Netting

Cornish Waters

Gill nets are efficient for catching spider crabs when they are on the move across the seabed. As they get so badly tangled the quality sometimes suffers and gill nets can have issues with accidental by catch of other non target species.

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How we rate fish

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Cornwall Good Seafood Guide rates fish on sustainability using a scale of 1 to 5.

1, 2 and 3 are recommended, Fish to avoid are rated 5.

We use the system devised by the Marine Conservation Society (MCS) so our scores are comparable with the scores produced by MCS for the UK and fisheries from all around the world. For more information on scoring click here.

Sustainability Overview

Although spider crab stocks are little studied the methods used to catch them have minimal impact on the environment and the current level of fishing is unlikely to have a detrimental effect on the stocks. Minimum landing sizes and licences for shell fishing are set by Cornwall Inshore Fisheries and Conservation Authority (CIFCA) who monitor and regulate this fishery. This is an underutilzed species and the majority of the spider crab catch is exported to Spain. It would benefit small scale, sustainable fishermen if a better UK market for this species could be developed. 

spider crab by Sarah McCartney

Biology

Spider crabs are scavengers that range over fairly large distances over the seabed. They have scissor like claws that are used to open shellfish and remove flesh from scavenged carcasses. They can live for up to 40 years. Females are smaller and are less marketable so are not landed by fishermen.  This species has a very low vulnerability to fishing 12 % (Ref Sealifebase.com). Female spider crabs with eggs are returned to the sea by fishermen, if buying a female spider crab check its is not carrying eggs by lifting the tail. 
 
 

Stock Info

Athtough this stock is relatively poorly studies according to Cornwall Sea Fisheries study of 2003-6 catch per unit effort was steady which is a good indication of sustainable levels of harvesting. Catches of spider crabs to Cornish ports has increased since the 90’s as the market has developed in Spain and now is fluctuating at around 400 tonnes per year. During the recession demand from Spain dipped with many fishermen finding that they couldn’t sell their catch in 2013. This species was included as an underutilsed species in the 2011 report produced by CEFAS. 

Management

Cornwall Inshore Fisheries and Conservation Authority manages shellfish licences and sets a minimum size for spider crabs. There is currently no quota or restriction on number of pots. Vessels over 15m in length are restricted by days at sea regulations in the Celtic sea. (ICES WGCRAB 2012). Shellfish fising is a licenced activity and fishermen must provide CIFCA detailed data on catches and fishing effort. 

Capture Info

Spider crabs are caught in nets or pots . There are several different designs of crab and lobster pots that are used by Cornish fishermen. Traditional ink pots were originally constructed from willow withy’s but nowadays pots are constructed from steel and nylon net with plastic fittings.  All are baited traps that allow crabs in but prevent them from easily escaping. Pots are dropped down to the seabed and are left for several hours or days before being retrieved. Any undersized crustaceans can be returned unharmed and in Cornwall there is little impact on the seabed on which the pots are deployed. Spider crab are also caught with gill nets. It is very difficult to pick out a spider crab as they become hopelessly tangled. Often the quality of the catch is not as good as pot caught and undersized ones if damaged are less likely to survey after being returned over the side. There are problems with accidental by catch of sharks, skates, cetaceans and seals in gill nets.  

References

Cornwall Sea Fisheries Committee, Cornish Inshore fishery Shellfish Stock Survey 2003- 2006
ICES WGCRAB 2012 report
MMO landings Data
Catchpole, T 2011, Identifying underutilzed species CEFAS 
www.sealifebase.org

Recipes for Spider Crab

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Sustainable alternative recipies

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