Mont St Michel commands one of the largest and most complex bays in the world. Out of the sea currents, in the pocket formed by Brittany and the Cotentin peninsula, Mont St Michel Bay (400 km2) opens out into the English Channel. The exceptional tidal range can reach 15 m during spring tides. The intertidal area covers 250km².
This Outer bay includes a 50 km2 Inner bay extending from Chapelle Sainte-Anne (Cherrueix) to Bec d'Andaine (Genêts). Covered in sands and mudflats, and salt marshes and meadows, it is also an estuary for three rivers, the Sée, the Sélune and the Couesnon.

Beneath a deceptively desert-like outward appearance, the sands and mudflats are teeming with wildlife. Living in the sediment or suspended in the sea-water are very tiny plants and animals - diatoms, micro-algae, mollusc and crustacean larvae... This primary production is consumed by farmed mussels and oysters as well as by numerous benthic invertebrates and mullet. Various seabed populations - macoma, cockles, shrimp, oysters, limpets etc. - and fish - including whiting, bass, flounder, mullet, salmon - also seals are frequent visitors to the sands and waters of the bay.

Covering almost 40 km², when grazed the salt marshes become the biggest expanse of salt meadows along the Atlantic seaboard of Europe. It has the most varied flora anywhere in France. These salt marshes produce organic matter and nutrients which are carried off by the spring tides to feed the abundant fauna buried under the sand and mud deposits. This positive feedback between the salt meadows and the coastal waters helps to make it such a good fishing area.

Mont St Michel Bay is a remarkably rich bird sanctuary, of international stature in terms of numbers. There are birds here for every season of the yearly cycle - wintering, migration, breeding, summering and moulting. These species occupy the estuary area - the beaches, salt meadows and polders - and the inland wetlands - channelled section of the Couesnon, inland marshes, Moidrey Cove etc.. Some of these birds are protected species.

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People have been reaping the benefits of the natural resources of the bay from time immemorial. Already in Gallo-Roman times - although no longer today - salt was produced by heating "tangue" (sandy-mud sediment) collected on the strand. During the 19th century, vast quantities of this "tangue" were used as farmland fertilizer. Nowadays, in the tourist age, with 3.2 million visitors a year to the Mont, the bay relies heavily on other activities to boost its economy and public image.

Some 13,000 salt meadow sheep graze 3,000 hectares of salt marshes in the bay. Their tasty meat is highly regarded by gourmets, a reputation that receives a great fillip from the tourist attraction at Mont St Michel.On the polders - land along the edge of the bay reclaimed from the sea - farmers grow a variety of crops: cereals and vegetables (carrots, onions, leeks, potatoes etc.).

The abundance of fish in the vast intertidal area explains the variety of fishing techniques, sometimes very old ones. Some of the stone or wooden fisheries date back to the 16th century. The fleet of trawlers from Cancale and Granville take mostly flat fish (sole, plaice etc.) and crustaceans with lobster pots. Shore fishing at low tide with shrimp nets, dragnets, gill nets, tangle nets, hoop nets occupies some dozen professionals and also informed amateurs, chiefly to the west of Mont St Michel.

Dredging for oysters became a thing of the past when the oyster beds were exhausted. New ways of farming oysters and mussels were introduced in the fifties and sixties. Raised on trays, the "hollow" oyster soon took over in the Bay of Cancale, the deep water flat oyster being costlier to produce.
Vertical mussel farms, where the mussels are raised on poles, is a high growth activity.
In 1997, output stood at some 1,000 tonnes of flat oysters, 4,000 hollow oysters and 10,000 tonnes of mussels. This is the leading industry on the Breton coastal sector of the bay, providing 1,000 jobs.

The Mont is a major place of pilgrimage; it reached its zenith in the 13th century, with the crossing seen us a rehearsal for the journey into the hereafter under St Michael's protection. Pilgrims still take this "path to heaven", although in smaller numbers than they used to.
Over the last fifteen years, a fresh angle has been brought to exploring the bay.
There now approved guides who present the bay's outstanding natural heritage, following the paths taken by our pilgrim forefathers.Each year, some 70,000 visitors enjoy crossing the bay with these official guides.

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