The only metric I'm using to assess the quality is how much a difference it makes to the species that we're protecting. If you create an MPA to protect some species, then you can measure if the species are coming back.
In Newfoundland, for instance, we have two MPAs that I'm familiar with: Eastport and Gilbert Bay. Eastport is in Newfoundland and Gilbert Bay is in Labrador. Neither of these are doing very well. They were created about 20 years ago. Eastport is not showing a significant increase in lobster, which is what is targeted there, because it's too small and it's not necessarily at the right place. Gilbert Bay has been problematic as well because the fish go in and out of the MPA and get fished outside, something they've tried to address. Those are examples of the complexity of those processes, which also link to my statement about the importance of adaptive management, the importance of revising our measures when we have additional science.