Hi John,
We went up there last October and had an awesome time. We didn't have that much luck landbased but off the jetty i know that everything from spanish mackeral to barramundi have been caught off it, quite a few octopus hang around it and pods of manta rays. You can also fish off the beach, we were staying at the furthest house thingo which was very nice but entailed a few long walks each day. I reckon that a landbased spot definintely worth trying would be the furthest point of the island, looking back at mainland AUS. There are some good eddies there that fish should congregate around. Another option is hiring a dinghy which we did and caught some bits and pieces and got smashed a few times by spanish mackeral fishing around a nearby island no too far from shore. There is a guy who runs charters from there and he is a fantastic guy, will PM you more info about that.
Cheers
Josh