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Lake freighters, or lakers, are bulk carrier vessels that ply the Great Lakes of North America. These vessels are traditionally called boats, although classified as ships. Lakers carry bulk cargoes of materials such as limestone, iron ore, grain, coal or salt from the mines and fields to the populous industrial areas down the lakes. The 63 commercial ports handled 173 million tons of cargo in 2006.〔(Welcome to Great Lakes Shipping ), quoting the US Army Corps of Engineers.〕 Because of winter ice on the lakes, the navigation season is not usually year-round. The Soo Locks and Welland Canal close from mid-January to late March, when most boats are laid up for maintenance. Crewmembers spend these months ashore. Depending on their application, lakers may also be referred to by their type, such as ''oreboats'' (primarily for iron ore), ''straight deckers'' (no self-unloading gear), ''bulkers'' (carry bulk cargo), ''sternenders'' (all cabins aft), ''self unloaders'' (with self unloading gear), ''longboats'' (due to their slender appearance), or ''lakeboats'', among others. In the mid-20th century, 300 lakers worked the Lakes, but by the early 21st century there were fewer than 140 active lakers.〔"Ship fans mourn scrapping of the Calumet", http://blog.mlive.com/grpress/2007/12/port_colborne_ontario_killer.html, Jim Nichols, Press News Service, December 30, 2007, accessed July 7, 2008.〕 One of the best known was the , which sank in 1975, the most recent and largest major vessel to be wrecked on the Lakes. ==Lakers vs. Salties== By way of the Saint Lawrence Seaway, smaller lakers have access to the ocean, and some ocean-going vessels have access to the Lakes. Visiting ocean-going vessels are called "salties". Many modern ocean going vessels are too large for the relatively small locks on the Saint Lawrence Seaway, so large salties cannot travel further inland than Montreal. Because one of the Soo Locks is larger than any Seaway lock, salties that can pass through the Seaway may travel anywhere in the Great Lakes. Similarly, the largest lakers are confined to the Upper Lakes (Superior, Michigan, Huron, Erie) because they are too large to use the Seaway locks, beginning at the Welland Canal that bypasses the Niagara River. Because of their deeper draft, and the lower buoyancy of fresh water, salties may accept partial loads on the Great Lakes, "topping off" upon exiting the Seaway. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Lake freighter」の詳細全文を読む スポンサード リンク
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