Wild Atlantic salmon, the most notable species, can weigh up to 12kg when fully grown.
It spends part of its time in freshwater rivers as well as in the sea, returning back to the river to spawn. Because of over-fishing and river pollution, wild salmon is in disturbingly short supply.
The distinctive pink flesh, which in the wild, is the result of a shellfish-based diet, is often achieved in farmed fish with the help of colouring agents.
Wild salmon also has a firmer flesh than farmed varieties. Because many farmed fish don't have space to develop and swim around in the water, their flesh has a tendency to be softer and fattier.
In the fishmongers, as with all fish, look for bright eyes and gills, firm flesh, and moist damp skin. It's also best cooked on the day of purchase.
In the kitchen
Innumerable culinary uses. An ideal fish for poaching, grilling and cooking on a griddle. Salmon is well-suited to cooking whole, or in smaller portions - fillets and steaks.
Cure fresh salmon at home with a traditional gravadlax - a Scandinavian dish of fresh salmon fillets steeped in dill, salt sugar and peppercorns.
Because of its rich flavour, salmon works well with lemony sauces such as hollandaise, or if served cold, mayonnaise. Piquant capers also provide bite and tangy contrast.
Poached salmon in Britain is traditionally served with mayonnaise, herby potato salad and a cucumber salad - a great summery dish.
Smoked salmon, although no longer an indulgence, makes an elegant complement to scrambled eggs. It's also great when blended with cream cheese, lemon juice and a touch of cayenne pepper.