According to an aboriginal affairs council, the current accepted population figure for the late 15th Century (closest figure estimate available for your date) is about 500,000 people.

http://en.m.wikipedia.org/wiki/Aboriginal_peoples_in_Canada

Other sources that may interest you

http://canadianarchaeology.com/caa/node/1388

http://books.google.ca/books?id=BPdgiysIVcgC&pg=PA12&lpg=PA12&dq=prehistoric+aboriginal+population+1500+canada&source=bl&ots=rTHOpKfX26&sig=mhkhnh5_HoDb9PxIXCv_q0k_qzs&hl=en&sa=X&ei=lb8XU9DTO8icrAHF54DoAg&ved=0CCYQ6AEwAw