Because you've seen it on several dives, it makes sense that it was likely speared in the park. Are visitors from the mainland diving in the park yet, or is it locals only? If it is a local, someone must know who would take a speargun into an MPA.
I don't think so, Phil. The wound looks like it may be old. Spearfishing is illegal in the park (as you know) and also in the waters off Avalon.