Gulf of St Lawrence

At Baie-Trinité, the Pointe-des-Monts Lighthouse, a National historic site of Canada, was built in 1829-1830 on a point that ancient geographers, since Samuel de Champlain (1567-1655) himself, classified as the demarcation point between the St. Lawrence River and the Gulf of St. Lawrence.

The Gulf of St. Lawrence is bounded on the north by the Labrador Peninsula and Quebec, to the east by Saint-Pierre and Newfoundland, to the south by the Nova Scotia peninsula and Cape Breton Island, and to the west by the Gaspé Peninsula, New Brunswick, and Quebec. As for significant islands the Gulf of St. Lawrence contains Anticosti Island, Prince Edward Island, Îles-de-la-Madeleine archipelago, Cape Breton Island, Saint Pierre Island, and Miquelon-Langlade.

Half of the ten provinces of Canada adjoin the Gulf: New Brunswick, Nova Scotia, Prince Edward Island, Newfoundland and Labrador, and Quebec.

Besides the Saint Lawrence River itself, significant streams emptying into the Gulf of Saint Lawrence include the Miramichi River, Natashquan River, Romaine River, Restigouche River, Margaree River, Humber River, Mingan River and others.

Branches of the Gulf include the Chaleur Bay, Fortune Bay, Miramichi Bay, St. George's Bay, Bay St. George, Bay of Islands, and Northumberland Strait.

According to Commission of Toponymy Quebec, the St. Lawrence River becomes the gulf at Pointe des Monts on the Côte-Nord and Matane Bas-Saint-Laurent or Sainte-Anne-des-Monts La Haute-Gaspésie, the Estuary is upstream, the Gulf of St. Lawrence, much wider, downstream.

• The great river becomes the Gulf of St Lawrence
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  From the top of Pointe-des-Monts Lighthouse, Pointe des Monts bedrock, gulf side (East) 2004
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  Pointe des Monts bedrock, Estuary side (West)
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  Whales watching near Anticosti Island 2004
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  Baie au Caplan, river flat, Anticosti Island 1995
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  Crevettier Manic V, 11853, at the wharf, La Haute-Gaspésie, Sainte-Anne-des-Monts 2002
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  Aerial view, bay of Sept Îles, port and city of Sept-Îles

• Lighthouses (some)
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  Bird Rocks, keepers'house and outbuildings, Magdalen Island
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  L'Anse-à-la-Cabane (Hamlet), Magdalen Island
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  Pointe-des-Monts, keeper's house and outbuildings

Outlets

The gulf flows into the Atlantic Ocean through the following outlets:

• The Strait of Belle Isle between Labrador and Newfoundland: between 15 kilometres (9.3 miles) and 60 kilometres (37 miles) wide and 60 metres (200 feet) deep at its deepest.
• The Cabot Strait between Newfoundland and Cape Breton Island: 104 km (65 mi) wide and 480 m (1,575 ft) deep at its deepest.

The Strait of Canso between Cape Breton Island and the Nova Scotia peninsula had been an outlet 1.0 km (0.6 mi) wide and 60 m (200 ft) deep at its deepest. Due to the construction of the Canso Causeway across the strait in 1955, it no longer permits exchange of water between the Gulf of Saint Lawrence and the Atlantic Ocean.

Limits

Since its appearance on maps, there has been no consensus on the last section of the St Lawrence River on its designation, whether it is an estuary or a gulf, what are its geographical limits and its hydrological entity ?

Mercator's map of 1569, the Jesuit Relations 1858, the History of French Canada since the Discovery, Abbé Lionel Groulx, 1960, the publications of the government of Canada, the Commission de Toponymie du Québec, doctoral theses and scientific research, do not provide an absolute answer.

According to Fisheries and Oceans Canada 2023, the Estuary and Gulf of St. Lawrence planning area covers most of the Estuary and Gulf of St. Lawrence bioregion, an area with some of the warmest surface waters in Atlantic Canada during summer and the largest amount of sea ice during winter. The planning area is approximately 240,000 km².

According to Encyclopedia Britannica, the name of gulf Saint Lawrence in a hydrologic context is not accurate, a gulf has to be considered more as a sea bordering the North American continent than as simply a river mouth.

The International Hydrographic Organization 1953 said: On the Northeast. A line running from Cape Bauld (North point of Kirpon Island, 51°40′N 55°25′W / 51.667°N 55.417°W / 51.667; -55.417) to the East extreme of Belle Isle and on to the Northeast Ledge (52°02′N 55°15′W / 52.033°N 55.250°W / 52.033; -55.250). Thence a line joining this ledge with the East extreme of Cape St. Charles (52°13'N) in Labrador.

On the Southeast. A line from Cape Canso (45°20′N 61°0′W / 45.333°N 61.000°W / 45.333; -61.000) to Red Point (45°35′N 60°45′W / 45.583°N 60.750°W / 45.583; -60.750) in Cape Breton Island, through this Island to Cape Breton [45°57′N 59°47′W / 45.950°N 59.783°W / 45.950; -59.783] and on to Pointe Blanche (46°45′N 56°11′W / 46.750°N 56.183°W / 46.750; -56.183) in the Island of St. Pierre, and thence to the southwest point of Morgan Island (46°51′N 55°49′W / 46.850°N 55.817°W / 46.850; -55.817).

On the West. The meridian of 64°30'W from Pointe-Jaune (49°04′N 64°30′W / 49.06°N 64.5°W / 49.06; -64.5) to Magpie (50°19′N 64°30′W / 50.31°N 64.5°W / 50.31; -64.5), but the whole of Anticosti Island is included in the Gulf.

Protected areas and national parks

St. Paul Island in Nova Scotia off the northeastern tip of Cape Breton Island, is known as the "Graveyard of the Gulf" because of its many shipwrecks. Access to this island is controlled by the Canadian Coast Guard.

In 1919 the first Migratory Bird Sanctuaries (MBS) in Canada were established under the Migratory Birds Convention Act on Bonaventure Island, on the Bird Rocks of the Magdalen Islands, and on the Percé Rock. These migratory bird sanctuaries are administered by the Canadian Wildlife Service.

The Federal Government of Canada manages the National Parks of Canada along the Gulf of Saint Lawrence at Forillon National Park on the eastern tip of the Gaspé Peninsula, Prince Edward Island National Park on the northern shore of the island, Kouchibouguac National Park on the northeastern coast of New Brunswick, Cape Breton Highlands National Park on the northern tip of Cape Breton Island, Gros Morne National Park on the west coast of Newfoundland, and a National Park Reserve in the Mingan Archipelago on the Côte-Nord of Quebec.^{[citation needed]}

The five provinces bordering the Gulf of Saint Lawrence have several provincial parks with protected coasts.^{[citation needed]}

Undersea features

The Laurentian Channel is a feature of the floor of the Gulf that was formed during previous ice ages, when the Continental Shelf was eroded by the Saint Lawrence River during the periods when the sea level plunged. The Laurentian Channel is about 290 m (950 ft) deep and about 1,250 km (780 mi) long from the Continental Shelf to the mouth of the Saint Lawrence River. Deep waters with temperatures between 2 and 6.5 °C (36 and 44 °F) enter the Gulf at the continental slope and are slowly advected up the channel by estuariane circulation. Over the 20th century, the bottom waters of the end of the channel (i.e. in the Saint Lawrence estuary) have become hypoxic.

The gulf has provided a historically important marine fishery for various First Nations that have lived on its shores for millennia and used its waters for transportation.^{[citation needed]}

The first documented voyage by a European in its waters was by the French explorer Jacques Cartier in the year 1534. Cartier named the shores of the Saint Lawrence River "The Country of Canadas", after an indigenous word meaning "village" or "settlement", thus naming the world's second largest country.

Basque whalers from Saint-Jean-de-Luz sailed into the Gulf of Saint Lawrence in 1530 and began whaling at Red Bay. They established their base on the Strait of Belle Isle and worked closely with the Iroquois in the Gulf of Saint Lawrence. In 1579 the English government closed all English ports to Spanish oil imports. As a result, a third of Basque whale oil could not be sold. Basque whaling collapsed in the Gulf of Saint Lawrence and never recovered.

• Anticosti Island
• Atlantic Ocean
• Estuary of St. Lawrence
• Maritime Peninsula
• St. Lawrence Seaway

• Rare plants of the Mingan Archipelago Environnement Canada, 2025 (French)
• The lighthouse Trail, Bas-Saint-Laurent, Gaspésie, Côte-Nord, Îles de la Madeleine (French)
• The New Map of Empire. How Britain Imagined America before Independence, Harvard University Press
• Mapping Land Tenure Pluralism in the St. Lawrence River Valley, Julia Lewandoski, essay kicks off a Borealia series on Cartography an Empire
• Légendes du Saint-Laurent, Récits des voyageurs, Jean-Claude Dupont, 1985, 72 pages (French)
• The Gulf of St. Lawrence - a Unique Ecosystem, Government of Canada 2005 [English | French]
• Timing and position of late Wisconsinan ice-margins on the upper slope seaward of Laurentian Channel David J. W. Piper et Adam Macdonald, 2001, 11 page