Just got off the phone with two of my buddies from back home. They both know the guy who claimed to catch it and said that hes a commercial baitfisherman. He provides all the pinfish for the bait shops in the area. Said he was a real good guy and really had no reason to lie about it.
The way that the water temperature is up there, the water has gotten so cold so fast in these last couple of weeks, that it is possible that this tuna just followed the mullet in from their offshore spawn.
the only two things that dictate fish movement are: water temp and bait. If the water temp is right and the bait is there, that means that the fish will be there. Now with all the displacement of habitat from the oil spill in the Norther Gulf, where these YF usually are, it is possible that this fish was just following the bait while trying to stay warm.