 In the spring of 1964 , the U.S. Fish and Wildlife Service released a report on the impact of dam construction on the Flats . The report strongly opposed construction of the dam , saying in part , " Nowhere in the history of water development in North America have the fish and wildlife losses anticipated to result from a single project been so overwhelming . " The report also pointed out the threat the dam would pose to the Yukon River 's large salmon population , which swim upstream each year to spawn . Arthur Laing , Canada 's minister of northern affairs and natural resources , also expressed alarm at the potential waterfowl losses and the threat the dam posed to Canada 's portion of the Yukon River salmon population . 
