Well, that's a good question, and I'm not sure I really know the answer.
A lot of it depends on the complexity. If you're talking about species protection, if you have a species you're trying to protect that's in very limited quantity, or is a mixed species, then it is a bit more complex to protect, in the sense that you can't allow many other fisheries because you could then have a bycatch issue or a problem such as that.
A single species in a single area is perhaps easier to protect because you can have a closure in effect that would only implicate that one fishery, as opposed to multiple fisheries.
Again, it's not necessarily the hardness; there's the complexity issue.