I have seen photos (when I worked as a fishing journalist) of groper taken from rock ledges in the lower South Island by North island LBG guys testing the area. Many were caught and released. I think from memory only two were actually kept and eaten.
They were taken in several different locations including lower West Coast, Fiordland and Catlins. There is a trick to finding them which basically involves looking for the deepest water possible in very rocky areas that boats cannot easily access and using crab for bait. It also involves walking very long distances with heavy packs and fishing remote and very dangerous locations. All normal LBG stuff really. Ropes are often used to get down to suitable ledges.