The changes that have been observed are mainly that the catch per unit effort, or how hard it is to catch a lobster, has improved. This means better and more stable catch rights, which was the objective in the first place because, as you recall, it was because of a decline—that's where the concern from the fishers came in. Since its establishment the catches have improved.
In addition to that, the lobsters inside the closed areas have been observed to be bigger. Again, when they are bigger, they are more productive. The females carry more eggs—better-quality eggs if you will—and that maintains the lobster catches around.