Denise,First of all I need to clarify what you mean by "recruiters". When you refer to recruiters, do you mean headhunters or internal corporate recruiters?
Let's break down the hiring process and discuss how jobs are filled, whether in Canada or abroad. First of all a position becomes available. The company usually makes this position available to anyone within the company first (internal posting), then afterwards if the position is not filled this way then the company will make use of it's internal database of resumes to source a candidate (also any internal referral program will be used at this point). If this becomes fruitless then there are external sourcing options (posting in job sites, career fairs, etc). If this doesn't work it is at this point that a company will choose to go with a headhunter to source a candidate. This is the way that most companies recruit. Now, of course, sometimes the position is extremely critical and all the options above are done at the same time. So, I can't say that all Canadian companies only deal with recruitment agencies or headhunters. Some do but it's too costly if the volumes are high.
In the end, the best way to get a jump on a position is by word of mouth and connections. Remember the adage: It's not who you know but what you know.
Denise, for a listing of recruitment firms across Canada, check out the site www.jobbus.com. It lists a comprehensive list of recruitment firms for all skill sets.
Best of Luck,
Harry