I don't know the specific answer to this question - You may want to start another subject line that asks how things work if you are transiting from the USA at YOW, but I can tell you in general the answer is yes - YOW is your port of entry into Canada, so you'll need to claim your bags as part of the Canada Customs exercise and then drop them onto another belt so they wind up on your flight to YVR.

How that exactly works at YOW will need to be explained by someone more familiar with YOW than me.