Nothing beats shellfish landed that morning

There is a particular pleasure in eating crab or lobster within sight of the water it came from, and it is not just sentiment. Most British coastal boats are day boats: pots are hauled in the early hours, landed by mid-morning and sold within hours, often straight off the quay. Shellfish that has never spent a week sitting on ice tastes sweeter, firmer and far more like the sea. If you are planning a coastal escape, build at least one meal around whatever has come in that day rather than deciding weeks in advance exactly what you want to eat.

The other advantage of buying at the coast is that you can talk to the people who caught it. They will tell you which species is good this week, how the weather has affected the catch and how they would cook it themselves — advice you will never get from a supermarket shelf.

Know what is in season

British shellfish has a rhythm, and eating with it means better flavour and better value. As a rough guide:

• Brown crab is landed all year, but the meat is at its fullest from late spring through autumn. A crab that has just moulted is disappointingly watery; one that has had a few months to fill out is dense and sweet.
• Spider crab is long-legged, sweet and often cheaper than brown crab. It is a late-winter and spring favourite in the south-west.
• Velvet swimming crab is small but intensely flavoured, best in spring and early summer, and excellent in soups or with pasta.
• Lobster is caught year-round, with the biggest landings and keenest prices from early summer to autumn. Winter lobster can be superb, simply scarcer.

Two things should always go back into the water: any shellfish below the minimum landing size, and any berried hen — a lobster or crab carrying a cluster of eggs under the tail. Both are protected by law, and both are essential to the next generation of stock. If you are offered one, politely decline.

Choose shellfish caught with care

Pot-caught shellfish is one of the least damaging fisheries around: pots are static, selective and mostly fish for a single species. You do not need a certificate to eat well, but you do need to ask a few sensible questions.

• Is it local? Ask which port it came from. Vague answers usually mean it has travelled.
• When was it landed? Crab in particular should be cooked within hours of landing, so "this morning" is the answer you want.
• How was it caught? Pots or creels are the answer; be wary of anything trawled.
• Buy from harbour-side sellers, fishermen's co-ops and market stalls rather than taking whatever is left at the back of a counter.

Local, seasonal and pot-caught is usually all three of sustainable, affordable and delicious.

Buying, storing and preparing at home

• Crab is nearly always sold cooked, because it must be cooked within hours of landing. Choose a heavy crab for its size, with a clean smell and no blackening at the joints. Keep it chilled and eat it within two days.
• Lobster should be bought alive and lively, with a tail that curls under when handled. Never buy one that is limp or already dead.
• Keep everything cold. A cool box with ice packs will get your purchase home safely. Ask for the shellfish to be bagged separately from anything else.
• To dispatch a lobster humanely, chill it in the freezer for twenty to thirty minutes, then kill it quickly with a sharp knife before cooking or splitting. If you are not confident, ask your fishmonger to do it for you.

If you have bought a live crab, cook it in heavily salted boiling water — around ten minutes for the first kilo, then a few minutes for each additional half kilo — and cool it quickly.

Simple ways to serve crab and lobster

Both need far less cooking than people imagine; the hard work happened at sea. Let the meat taste of itself.

• A proper crab sandwich: white meat, good mayonnaise, a squeeze of lemon, a pinch of cayenne, on thick white bloomer or sourdough. Keep any salad dry so the bread does not go soggy.
• Dressed crab: white meat on one side of the shell, brown meat on the other, the brown mixed with a little fresh breadcrumb, parsley and lemon. Serve cold with brown bread and butter.
• Grilled lobster: split it, brush the cut side with melted butter, and grill cut side up for two or three minutes until just opaque. Nothing more is needed.
• Cold lobster: with mayonnaise, new potatoes and a sharp dressed salad — the classic summer coastal lunch.
• Crab with pasta or on toast: warm the brown meat gently with garlic, chilli and a splash of cider, then fold through the white meat at the last moment.

Salt, lemon, butter, black pepper and good bread will do more for crab and lobster than any elaborate sauce. Avoid drowning either in cream or cheese.

Eating out and beside the sea

The best coastal eating is often the least formal: a harbour café with plastic chairs, a pub garden above a slipway, a stall selling crab rolls until they sell out. Ask where the shellfish came from and when it was landed; a good kitchen will answer without hesitating. Short menus that change with the boats are a better sign than a laminated list of everything.

For a beach picnic, take a dressed crab in a cool bag with plenty of ice packs, a lemon, a knife, brown bread and a bag for the shell. Find a wall out of the wind, eat it within the hour, and keep half an eye on the gulls — they are quicker than you are.