Starting March 15, 2016, visa-exempt foreign nationals who fly to or transit through Canada will need an Electronic Travel Authorization (eTA). Exceptions include U.S. citizens and travellers with a valid visa.
Find out what you need to visit Canada as a tourist or business person, how to extend your stay in Canada and what documents you need to carry with you to transit through Canada. http://www.cic.gc.ca/english/visit/index.asp