You do if the price shown is in Canadian dollars. Well, you don't have to but to know whether or not you are getting a fair price you want to know the exchange rate.
If the supply of bitcoins was variable and targeted to provide price stability then you might be able to do that. But Bitcoin's supply is fixed. So prices in terms of BTCs will rise and fall based on a number of factors. With electronic systems, comparing prices, even when they are constantly changing, is not much of a big deal. That's why you'll often see a price shown in both BTCs and USDs, where either may change minute-to-minute based on various factors.