Begin With Your Eyes

A good coastal market feels bracing: cold air, wet concrete, and trestle tables piled with ice. Before you taste anything or part with a penny, use your eyes. A whole fish should look as though it has just come out of the water — eyes bright, clear and slightly domed, not sunken, cloudy or grey-rimmed. The skin ought to be taut and glossy, with a sheen that catches the light, and the scales should sit tight rather than flaking off on your fingers.

Now lift the gill flap. Inside you want deep pink to bright red, clean and slightly damp, with no sour or musty edge to it. Brown, grey or slimy gills tell you the fish has been out of the water too long. Finally, press the flesh along the back with a clean finger. It should spring back immediately and leave no dent behind. Soft flesh that holds the imprint of your thumb is a fish to walk past.

Use Your Nose

Fresh fish smells of the sea and very little else — clean, briny, faintly of cucumber or wet stone. What you are looking for is the absence of smell as much as anything. Ammonia, sharp sourness, or that heavy, sweetish tang you get around old ice are all signals to move on.

Judge the whole stall, not just the single fish you fancied. If the slab smells clean but one specimen smells wrong, ask for a different one. If the entire display carries a smell that makes you step back, buy your lunch elsewhere. Nobody minds if you ask to smell before you buy — the good stallholders expect it and will happily hand you a fish to sniff.

Shellfish, Crustaceans and the Signs of Life

With shellfish you are buying something alive, so the rules change slightly. Mussels, clams and cockles should have tightly closed shells, or close firmly when you tap them. Wet, heavy and cold is what you want; light and rattly means they are empty or dying. Oysters should be shut tight and full of liquor when opened, never gaping.

Crab and lobster should feel heavy for their size, with all limbs accounted for, legs tucked in, and no black spotting or powdery shells. Choose the liveliest one in the tank. Prawns should have firm heads, glossy translucent shells and no blackening at the neck; pinch the tail and it should curl back smartly. Scallops want to be plump and ivory-white with the coral roe still attached, sitting in their own clear liquid rather than a milky puddle. Squid should have speckled skin and clear eyes.

• Mussels and clams: closed shells, or closing when tapped — discard any that refuse to respond.
• Oysters: tightly shut, heavy, smelling of clean sea.
• Crab and lobster: heavy, wet, lively, with every limb intact.
• Prawns: firm heads, glossy shells, no black spots at the neck.
• Scallops: plump, translucent-white, coral roe attached, no milky liquid pooling.

Ask Two or Three Good Questions

The single best question at a coastal market is simply: “What came in this morning?” A stallholder who knows their stock will light up and point you towards the best of it. Follow up with a few practical ones.

• When was this landed?
• Is it wild or farmed?
• Has it been frozen, and when?
• How should I cook it, and how long will it keep?

Frozen at sea is not a fault — plenty of excellent fish is frozen within hours of being caught — but it does change the texture and how you should cook it, so it is worth knowing. A good fishmonger will steer you away from the tired fish and towards the better value, because they want you back next week. If you get a shrug instead of an answer, take your custom down the row.

Time It Right

Mornings beat afternoons. Most boats land early, and stalls are at their best by mid-morning, before the sun has had a chance to work on the ice. Weekdays are quieter than Saturdays, which means more time, a better conversation and a keener price. Ask about tides and landing days, too: some markets fill up an hour or two after high water, and a few stalls only appear on the days the boats actually come in. Buy on landing day rather than the day after, and never be tempted by a tray that has been sitting in the sun all afternoon.

Getting It Home, and Keeping It Honest

Take a cool bag and a couple of ice packs with you, and ask the stall for a handful of ice on the way out. At home, shellfish goes at the bottom of the fridge in a bowl under a damp cloth — never in a sealed bag of tap water, which kills them. Fish goes on a plate, covered, on the bottom shelf, in the coldest part of the fridge. Cook shellfish the day you buy it where you can, and fish within a day or two.

That final sniff when you unwrap it at home is the last and best test. If it smells wrong, don't cook it and don't eat it. Buy a little and often, buy what you will cook tonight, and you will eat far better than any supermarket counter can manage.