A couple months ago, the Newspaper Audience Databank (NADbank) and the Print Measurement Bureau (PMB) released their Spring 2015 survey of readership numbers for its member newspapers and magazines.
If you need readership (not circulation) numbers of some Canadian newspapers and magazines to help with your photography pricing, then have a look at this list which uses 2014 data. Readership numbers are typically much higher than the corresponding print circulation numbers.
This is more for commercial photography that will appear in these publications and not so much for editorial. While many publications have “fixed” rates for editorial photography, some do have wiggle room to negotiate higher rates.
The days of pricing photography based on circulation still exist but it may be more accurate to price based on readership especially since that’s how some publications charge their advertisers.