Blue shark

Pat it dry, brush with oil and season, then grill or sear over medium-high heat for about 3–4 minutes per side for a steak around 2 cm thick. Take it off the heat when the centre is opaque and flakes easily; its lean flesh dries out if cooked for too long.

No, not if it smells clean and mild. A strong ammonia-like smell is a warning that the fish is no longer fresh; soaking it in milk or lemon will not make spoiled fish safe.

Keep it covered in the coldest part of the fridge and cook it within 1–2 days of buying. For longer storage, wrap it airtight and freeze it; thaw it in the fridge, not on the worktop.

It is safest to cook it thoroughly rather than serve it raw or barely cooked. Cook the centre to 63 °C, then let it rest briefly before serving.

Its firm, mild flesh works with lemon, garlic, parsley and capers, and it pairs well with roast potatoes or grilled vegetables. Cut it into chunks for a curry or kebabs, taking care not to overcook it.

Yes: blue ling is a mild fish that works in many of the same dishes, though its flesh is usually less firm. Blue ling has 18.9 g of protein per 100 g, compared with 15 g in blue shark.

A 100 g portion provides 15 g of protein. Serve it as a steak or cut it into pieces for a curry, with vegetables or another side.