@07
At 300 hours you are 450 hours short of meeting the minimum requirement to write the Canadian SAMRA and SARON exams. Also note that the exams expire 24 months to the day once you've written them so you must meet all ATPL flight hour requirements by then or the exams lapse - this is part of the reason there is no such thing as a "Frozen ATPL" in Canada.
You could potentially write the IATRA exam which is what you would need to fly, say a Dash-8, Saab 340 or similar, however at 300 hours you'll be looking at 2 years of ramp work before you saw right seat here in Canada (Assuming you have the legal right to work here in the first place), by which point the IATRA exam would have already expired.
I've posted a link to the Transport Canada standard outlining the ATPL requirements:
Part IV - Personnel Licensing and Training - Transport Canada