To many visitors to the seashore, crabs are probably the most popular and best-known animals. They are encountered in abundance on rocky shores, in salt-marshes and in pools on sandy beaches.
Crabs are the most advanced members of the phylum Crustacea. True crabs belong to the sub-order Brachyura. 73 brachyuran crab species and/or subspecies have been reported from the temperate waters of the north-eastern Atlantic, with 54 species occurring within British and Irish waters. These 54 species (excluding casuals) are described in this Synopsis.
Brachyuran (or ‘true’) crabs can be distinguished from the three species of anomuran (or ‘false’) crabs occurring in British waters. For more information about these species, see Synopsis 55 (Lobsters, mud shrimps and anomuran crabs).