River Tay River Tay The River Tay () is the longest river in Scotland and the seventh-longest in the United Kingdom. The Tay originates in western Scotland on the slopes of Ben Lui (), then flows easterly across the Highlands, through Loch Dochart, Loch Iubhair and Loch Tay, then continues east through Strathtay (see Strath), in the centre of Scotland, then southeasterly through Perth, where it becomes tidal, to its mouth at the Firth of Tay, south of Dundee. It is the largest river in the UK by measured discharge. Its catchment is approximately , the Tweed's is and the Spey's is
River Tay froze over as far as the Tay Road Bridge, and ice floes remained for weeks despite a thaw. Several places along the Tay take their names from it, or are believed to have done so: The river is of high biodiversity value and is both a Site of Special Scientific Interest (SSSI) and a Special Area of Conservation. The SAC designation notes the river's importance for salmon ("Salmo salar"), otters ("Lutra lutra"), brook lampreys ("Lampetra planeri"), river lampreys ("Lampetra fluviatilis"), and sea lampreys ("Petromyzon marinus") . Tha Tay also maintains flagship population of Freshwater pearl mussel ("Margaritifea margaritifera"). Freshwater pearl