List of longest rivers of Canada
Nine rivers in this list cross international boundaries or form them. Four—the Yukon, Columbia, Porcupine, and Kootenay—begin in Canada and flow into the United States. Five—the Milk, Pend d'Oreille, Saint Lawrence, Red, and Saint John—begin in the United States and flow into Canada. Of these, the Milk and the Kootenay cross the international border twice, the Milk leaving and then re-entering the United States, the Kootenay leaving and then re-entering Canada. The drainage basins of these nine rivers extend into both countries; in addition, the drainage basins of six others—the Fraser, Assiniboine, South Saskatchewan, Saskatchewan, Nelson, and Winnipeg—extend into the United States even though their main stems flow entirely within Canada.
Petitcodiac River
Six species have disappeared from the river since the mid-1980s. The Petitcodiac River was the only known Canadian habitat of the dwarf wedgemussel, and was later isolated to just nine American watersheds after its elimination from the Petitcodiac. The Atlantic salmon is no longer present in the watershed, and has since been listed as an endangered species in Canada. The American shad was a favourite with fishermen, and represented two-thirds of the entire Canadian shad landings from 1870 to 1900; catches peaked at  million kilograms (two to six million pounds) per year. Three other species have been eliminated from the river: the striped bass, the Atlantic sturgeon, and the Atlantic tomcod. However, a project of the Petitcodiac Riverkeeper, funded by the Government of Canada's Environmental Damage Fund in 2005, noted that the removal of the causeway would result in a "good" chance of bringing back the eliminated species, and an "excellent" chance of increasing the numbers of species deemed to have been reduced in numbers. No data has been released for the Atlantic salmon or the striped bass.