The Oceans Act is pretty clear. That's what your study is about: the Oceans Act MPAs. Section 35 gives five reasons for establishing a marine protected area for “special protection”. That's special protection of habitat or species, or for any other reason the minister designates. It's not sustainable use. It's for special protection.
As I've said, so far under that act, it's less than 1% of Canada's oceans. For 99% of the oceans it's business as usual.
The 10% target by 2020 may seem arbitrary, but targets are often used in conventions and laws, and this one is in law.