A Fish Made for the Harbour Wall

There is a particular pleasure in eating mackerel within sight of the water it came from. The fish is rich, oily and forgiving, which makes it ideal for a barbecue, and it cooks in minutes — a mercy when the sea breeze is blowing and everyone is hungry.

Whether you have caught your own on a feather trace or bought a brace from a coastal fishmonger, the principles are the same. Mackerel is best treated simply: high heat, a short cooking time, and a marinade or seasoning that cuts through the oil rather than smothering it.

Choosing and Preparing Your Fish

Freshness matters more than anything else. Look for bright, clear eyes, firm flesh that springs back when pressed, and a clean smell of the sea rather than anything sharp or ammonia-like. A mackerel that was swimming this morning will taste better than any marinade can improve.

Ask your fishmonger to gut and fillet it, or do it yourself on a board at home. Once filleted, run a finger along the centre line to check for stray pin bones and pull them out with tweezers or pliers. Rinse briefly in cold water and pat thoroughly dry with kitchen paper — wet fish steams rather than browns.

If you are cooking whole, slash the flanks two or three times on each side so heat and marinade penetrate. Leave the heads on or off as you prefer; they add flavour but take up space.

• Two fillets per person is a generous portion; one large fillet each is plenty with bread and salad.
• Keep fish in a cool box on ice until you are ready to cook, never in direct sun.
• Avoid leaving mackerel at room temperature for more than half an hour.

Simple Marinades That Flatter the Fish

Mackerel's oiliness means it stands up to bold flavours, but restraint pays. Acid, salt, a little sweetness and an aromatic herb are the building blocks. Thirty to sixty minutes is enough; longer than two hours and the acid will start to break down the flesh.

Try these combinations, whisked together in a bowl and brushed or poured over the fillets:

• Lemon and thyme: the juice and zest of one lemon, three tablespoons of olive oil, a crushed garlic clove and a handful of fresh thyme leaves.
• Soy and ginger: two tablespoons of light soy sauce, one of honey, a thumb of grated ginger and a splash of rice vinegar. Excellent on fillets cooked directly over coals.
• Mustard and dill: two teaspoons of Dijon mustard, three tablespoons of rapeseed oil, a squeeze of lemon and plenty of chopped dill. Very good with whole fish.
• Harissa and yoghurt: a tablespoon of rose harissa stirred into four tablespoons of thick yoghurt, with a pinch of salt. Brush on just before cooking and serve the rest alongside.

Season with flaky sea salt and black pepper just before the fish hits the grill. Salt too early and it will draw out moisture.

Foil Parcels: The Forgiving Method

If the wind is up or you are cooking on a disposable barbecue with uneven heat, foil parcels are your friend. They trap steam, keep the fish moist, and are almost impossible to ruin.

Tear off a sheet of foil large enough to wrap a fillet loosely, with room for air to circulate. Place the fish skin-side down on a bed of sliced fennel, onion or courgette, add a knob of butter or a spoonful of your marinade, and bring the edges together to make a sealed tent. Cook over medium coals for eight to ten minutes, turning the parcel once. The fish is done when the flesh flakes at the thickest point and has turned opaque.

Open the parcel carefully — the steam is fierce — and finish the fillet skin-side down on the bars for a minute to crisp the skin if you like.

Direct Grilling: Hot and Fast

For the classic approach, you want a hot, clean grill and a lightly oiled fish. Mackerel skin is delicate and sticks beautifully to cold or dirty bars, so scrub the grate and rub it with an oiled cloth or half an onion before you start.

Lay fillets skin-side down and leave them alone for three to four minutes. Resist the urge to prod. When the flesh has turned opaque most of the way up the side, slide a thin fish slice underneath and turn once. Give it another two minutes on the flesh side. A whole fish takes six to eight minutes per side over medium coals, depending on size.

Watch for flare-ups. Mackerel drips fat, and fat on coals makes flames that will blacken the skin before the flesh is cooked. Keep a spray bottle of water, or a lidded section of the barbecue with no coals, to move fish to if things get lively.

Serving It, Harbour-Style

Mackerel waits for no one. Serve it straight from the grill with lemon wedges, a bowl of new potatoes tossed in butter and parsley, and something sharp — pickled cucumber, a tomato and red onion salad, or simply bread and salted butter.

If you have cooked in foil parcels, spoon the buttery juices over the fish at the table. A cold lager, a dry cider or a crisp white wine all work well.

And when you are finished, bag up your rubbish and take it home. Leaving a harbour wall clean for the next angler or family is part of the pleasure of cooking outdoors by the sea.