"When you get a check from Neteller, is information sent to the Canadian government about it? Does it create a tax liabilty for you? Is so, what percentage?"
When I used to get cheques, nothing as far as I know was reported to the government about them. As for your tax liability, other posters are (to my understanding) essentially correct - if poker is your main/sole source of income, you are supposed to file, and if it is a recreation/side income, you don't. You should consult with a tax specialist to confirm however.