That's a big question with many parts. If you went back to the history of the haddock box, when it was first established as a no-take area, it wasn't a very popular measure. Now I think you would be hard-pressed to stop it from being a no-take area, because it's so popular.
The literature on spillover effect is pretty messy. There are some clear examples where it works, and some clear examples where it doesn't work. It's pretty messy scientifically.
It's pretty clear it works for many different kinds of species, and sometimes it works for surprising species. There are small enclosures in the gulf islands off California, where you get really surprising spillover effects. People said it would never work for that species because it's a migratory species, but you see spillover effects outside these rather small protected areas.
There is no uncertainty that it's a changing and dramatic world. If you look at the elements of sustainability: social, economic and ecological. The ecological part of that is the most brittle. The social one is the most highly adaptive. We've changed on a dime with changing economic conditions. Fishers have been good at doing that for a long time. In the Bay of Fundy, they're fishing lobster now where they used to fish herring weirs.
I know it's hard to be displaced and I recognize that significance, but I think there are benefits to fishers in having marine protected areas. I wouldn't be arguing for it so strongly if there weren't. There are real benefits in managing oceans sustainably.
I don't know if that's a good answer to your question, but—