Great Lakes are estimated at 900 trillion. The influx of parasitic lamprey populations after the development of the Erie Canal and the much later Welland Canal led to the two federal governments of the US and Canada working on joint proposals to control it. By the mid-1950s, the lake trout populations of Lakes Michigan and Huron were reduced, with the lamprey deemed largely to blame. This led to the launch of the bi-national Great Lakes Fishery Commission. "The Great Lakes: An Environmental Atlas and Resource Book" (1972) noted: "Only pockets remain of the once large commercial fishery." But, water quality improvements realized
Teltow Canal Berlin's eastern suburbs. The Dahme provides a link to the Oder-Spree Canal, and hence to the River Oder and Poland. Whilst the Dahme is a tributary of the River Spree, itself a navigable tributary of the Havel, the Teltow Canal offers the advantage of bypassing the centre of Berlin, with its heavy river traffic. At its western end, the Teltow Canal incorporates the Griebnitzsee lake which links to the Havel in Potsdam. The Griebnitz Canal provides a second link to the Havel from the eastern end of the Griebnitzsee. Towards its eastern end, the Teltow Canal is linked to the