Crayfish, Crawfish, Spiny lobster, Palinurus elephas

The magnificent crayfish is one of the most impressive seabed animals in Scottish waters. Bright yellow-orange in colour, often with purple tinges, this big crustacean can grow up to 60cm long, plus a pair of strong antennae even longer than its body. A crayfish has small front claws, but it is heavily armoured with strong spines: good defence against most predators.

Where do they live?

Crayfish live mainly off western coasts of Britain and Ireland, north to Shetland, and with only occasional records from the north-east coast. They also live in warmer waters to the south of Britain, to the Canary Isles and Mediterranean. In Britain, crayfish are currently at their northerly limits, so it is likely that climate change will affect their distribution around Britain.

Crayfish are generally found in open coastal areas and offshore seabeds. Inshore, crayfish prefer rocky or mixed seabeds, with relatively large crevices or boulder holes for protection. They usually live deeper than 15m, and move offshore during their periodic migrations to deeper water.

How do they live?

Crayfish often live in groups in rock crevices, with their long antennae poking out. They are scavengers, using their small front limbs to collect food from the seabed. Their big eyes allow them to be more active by night, but they may also be seen during the day. Apart from humans, crayfish have few predators, but using powerful tail muscles they can rapidly 'jack-knife' away from any threats. When in its crevice, the crayfish can use its strong spines to jam itself in, making it difficult to extract

Crayfish make loud clicking and creaking noises underwater by rubbing the bases of their antennae. Prior to mating, female crayfish attract males by making a particular noise known as 'stridulating'. Crayfish are mature from a size of around 10cm carapace length. They mate in summer, then the females carry eggs for up to nine months, often moving into deeper water to over-winter while the embryos mature. Upon hatching the larvae drift and feed in the plankton before settling on the seabed as miniature adults. At this stage they are very vulnerable, and require a suitable seabed until they are large enough to fend for themselves

Why worry about crayfish?

Crayfish fisheries provide small but locally important industries, but populations of this beautiful animal have declined considerably since the 1970s, with reduced fishery landings and a smaller average size caught. Traditionally taken in pots and creels, the more recent use of capture methods such as tangle netting is a likely reason for stock depletion; their spiny bodies being easily entangled in nets. Environmental conditions may also play an important role, especially in recruitment and survival of larvae. The presence of crayfish only on Atlantic coasts suggests that they prefer oceanic water, and they may respond to changes in water quality. The crayfish is a priority species for the UK Biodiversity Action Plan.