In the US, nearly 1,400 Pacific salmon populations have been wiped out since the arrival of European settlers.
(The most important factors that affect salmon are the "four Hs"—hydropower, habitat, harvest, and hatcheries. To help reduce mortality of juvenile salmon as they encounter dams and hydroelectric turbines on their downstream migration, fishery managers and biologists transport critical populations in barges and trucks. Hitch Hiking Salmon - Madness.)
Source: Salmon Decline and Recovery - http://www.waterencyclopedia.com/Re-St/Salmon-Decline-and-Recovery.html#ixzz0q6gCzZXH