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Full types of shellfish guide
How to spot it, where it lives, how it is caught and how to cook it — the complete guide, in one easy read.
Shellfish is a term used to describe aquatic invertebrates (having no backbone). These invertebrates also have an exoskeleton meaning that their skeleton is on the outside not the inside like ours. Details of how each of these animals grow is given for each species.
Most types of shellfish are a highly prized seafood, especially lobster.
What is shellfish?
Shellfish is the everyday word for edible aquatic animals that have no backbone — they are invertebrates — and wear their skeleton on the outside as a shell or exoskeleton. They fall into two broad families: crustaceans and molluscs. Shellfish are covered by two of the United Kingdom's fourteen named food allergens, crustaceans and molluscs, so they are always worth flagging on a menu.
Types of shellfish: a quick list
Crustaceans: brown crab, spider crab, velvet crab, lobster, langoustine (also called scampi or Dublin Bay prawn), prawns, shrimp and crayfish.
Bivalve molluscs, with two hinged shells: mussels, oysters, scallops, queen scallops, clams, cockles and razor clams.
Gastropod molluscs, with a single shell: whelks, winkles (periwinkles) and limpets.
Cephalopod molluscs: squid, cuttlefish and octopus. They have no outer shell, but they are molluscs and are covered by the mollusc allergen.
Crustaceans
Crustaceans have a jointed exoskeleton and several pairs of legs. The ones you are most likely to meet around Britain are crab, lobster, langoustine (the Dublin Bay prawn), crayfish, prawns and shrimp. They are lively, characterful creatures, which is exactly why freshness — buying them alive — matters so much.
Molluscs
Molluscs have a soft body protected by a hard shell. The bivalves, with two hinged shells, include mussels, oysters, scallops, clams and cockles, while the gastropods — single-shelled members of the snail family — include whelks, winkles and limpets. Commercial purification is a controlled process, not a guarantee that every hazard has been removed. Buy from a reputable supplier and follow current alerts, storage and cooking instructions.
Which shellfish to choose
If you are new to shellfish, mussels are a friendly and affordable place to start, with crab and scallops close behind, and lobster saved for a special occasion. Whichever you choose, our buying, preparing, cooking and eating guides walk you gently through every step.
Which shellfish come from UK waters?
British waters, including Cornwall's, are known for brown crab, spider crab, lobster, langoustine, scallops, mussels, oysters, whelks and cockles, and a large share of the UK catch is exported. Two oysters are sold here: the native oyster, which is flat and round, and the Pacific or rock oyster, which has a deeper, frillier shell and makes up most of the oysters on sale. Squid and cuttlefish are landed in Cornwall too, mainly in autumn and winter.
Shellfish and food safety
Shellfish need more care than most foods. Filter-feeding molluscs such as mussels and oysters can concentrate bacteria, viruses and natural toxins from the water around them. Buy from a reputable supplier, keep shellfish cold and cook them thoroughly unless they are sold specifically for eating raw. The NHS advises people who are pregnant to avoid raw shellfish, and anyone very young, elderly or with a weakened immune system should be cautious too. Do not gather wild shellfish to eat without checking local advice first; our cockles and mussels safety guide explains what to check.
FAQs
Quick fish questions
Short answers for the questions families and coastal readers often ask first.
What are the main types of shellfish?
Shellfish fall into two families: crustaceans (crab, lobster, langoustine, prawn, shrimp and crayfish) and molluscs (mussels, oysters, scallops, clams and cockles, plus whelks, winkles and limpets).
What is the difference between crustaceans and molluscs?
Crustaceans have a jointed external shell and several pairs of legs; molluscs have a soft body inside a hard shell — either two hinged shells (bivalves) or a single coiled shell (gastropods).
Is shellfish a fish?
No. Shellfish are aquatic invertebrates, meaning they have no backbone and wear their skeleton on the outside. They are a separate group from finned fish, and are covered by two of the UK's fourteen named food allergens, crustaceans and molluscs.
What are bivalves and gastropods?
Bivalves are molluscs with two hinged shells — mussels, oysters, scallops, clams and cockles. Gastropods are single-shelled members of the snail family, such as whelks, winkles and limpets.
Which shellfish is best for beginners?
Mussels are a friendly, affordable place to start, with crab and scallops close behind. Lobster is the showstopper for a special occasion. Our buying, preparing and cooking guides walk you through each.
What is the full list of shellfish eaten in the UK?
On the crustacean side, UK shellfish include brown crab, lobster, langoustine, crayfish, prawns and shrimp. On the mollusc side they include mussels, oysters, scallops, clams and cockles, plus gastropods such as whelks, winkles and limpets. Squid, cuttlefish and octopus are also molluscs and are grouped with shellfish for allergen purposes.
Is a crab a shellfish?
Yes. Crab is a crustacean, one of the two families that make up shellfish, alongside lobster, prawns and langoustine. Crustaceans are a separate named allergen from molluscs, so a crab allergy does not automatically mean you react to mussels or oysters.
Are mussels and oysters shellfish?
Yes. Mussels and oysters are molluscs, specifically bivalves, which have two hinged shells. They sit in the mollusc family of shellfish rather than the crustacean family that crab and lobster belong to, though both families are covered by UK allergen labelling rules.
What is the difference between a prawn and a shrimp?
In the UK the words are often used interchangeably, but prawns are generally the larger crustacean and shrimp the smaller. Both are crustaceans, so they share the same shellfish allergen group, and both are best cooked just until the flesh turns opaque and firm.
Can you be allergic to crustaceans but not molluscs?
Yes. UK food law lists crustaceans and molluscs as two separate named allergens, so some people react to one group and not the other. Anyone with a shellfish allergy should check which family a dish contains, as a prawn allergy does not always extend to mussels, scallops or oysters.
What are 10 types of shellfish?
Crab, lobster, langoustine, prawns, mussels, oysters, scallops, clams, cockles and whelks are ten of the most common. Squid, cuttlefish and octopus are also molluscs and count as shellfish for allergen labelling.
Is squid a shellfish?
For food and allergen purposes, yes. Squid has no outer shell, but it is a mollusc, so it is covered by the mollusc allergen along with mussels, oysters and scallops.
