Re: Canada. You'd have to check with Canadian law about shipping fish, but I know there are dealers shipping fish up there and vice versa (down here) without issues. As long as the fish don't violate any CITES restricted species you should be o.k., although you may be required to provide an official customs health certificate from your country of origin to be inspected at the port of entry.
NOTICE:There have been some changes in the USPS's 2-3 day priority mail service. This service is no longer an expedited delivery service nor is it treated as such. They have the option to deliver a 2-3 day package UP TO FOURTEEN DAYS from the postmark as of January 1st, 2007. I wasn't aware of the new change and shipped out two boxes this past monday (the 22nd) of baby kribs with 60 hour heat packs, and so i'm tracking the numbers this morning and one has had no updates past "package accepted," and the other says "en route January 28th," which is funny because today is the 25th.
I managed to dial through the gauntlet of USPS voicemail to reach a live person, and they said, "well, we have up to two weeks to deliver this mail. Your postmaster should have told you to ship the fish overnight." Great. Just lovely. In the middle of winter, these fish are going to be lucky if they don't arrive in a solid block of ice.
SO FAIR WARNING about using USPS's 2-3 day priority mail from now on. This sucks.
