Five Canadian provinces share one great-lakes gateway gulf
The Gulf of St. Lawrence funnels Great Lakes water to the Atlantic through the St. Lawrence River. Its shores touch half of Canada’s ten provinces—Quebec, Nova Scotia, New Brunswick, Newfoundland and Labrador, and Prince Edward Island—along with the small French islands of Saint-Pierre and Miquelon, a leftover scrap of France in North America.
Nobody agrees exactly where river ends and gulf begins, or even whether it counts as an estuary. Quebec’s naming commission puts the switch near Pointe des Monts, where a lighthouse went up in 1829–1830 on a spot mapmakers since Samuel de Champlain have treated as the dividing line. Downstream, the gulf holds Anticosti, Prince Edward Island, Cape Breton and the Îles-de-la-Madeleine, and the Miramichi, Restigouche, Humber and Romaine rivers pour in. Fisheries and Oceans Canada’s planning zone covers about 240,000 square kilometres, with some of Atlantic Canada’s warmest summer surface water.
Water leaves by several doors. Cabot Strait, about 56 miles wide, opens between Cape Ray and Cape North, while the Strait of Belle Isle squeezes to 15 kilometres at its narrowest and only 60 metres deep. The Strait of Canso stopped exchanging water in 1955 once a causeway blocked it. On the floor, the Laurentian Channel, carved when ice-age seas dropped, runs about 1,250 kilometres at roughly 290 metres deep, and its innermost bottom water turned hypoxic over the twentieth century.
First Nations fished and travelled these waters for millennia. Jacques Cartier made the first documented European voyage in 1534, borrowing an Indigenous word for village that became Canada. Basque whalers from Saint-Jean-de-Luz arrived around 1530 and worked from Red Bay, but after England shut its ports to Spanish oil in 1579 a third of their oil went unsold and the trade collapsed for good.
From December, ice forms between Montreal and Quebec City and drifts seaward, and by January and February it covers the whole gulf, damping waves that would otherwise glaze ships. Thirteen whale and dolphin species live here. St. Paul Island earned the nickname Graveyard of the Gulf for its wrecks. Canada’s first migratory bird sanctuaries opened in 1919 on Bonaventure Island, Percé Rock and the Magdalen Bird Rocks, and a coral conservation zone in western Honguedo Strait followed a 2018 agreement.
Source: Gulf of St. Lawrence
