We troll 2 of these, below surface, in combination, with the rigs on surface, doesn't cost any more fuel or time. Pay attention, to what time the bite has been, early, noon, late afternoon, in the area your fishing. If you pay attention, you will see a pattern forming. I know a NJ, fisherman, who always, takes his first fish, before the 6th of June, thats 6 days, after the opening of the season. Look at NC, the fishing there is unheard of in the North.
Food is the key, for tuna.
Present the food in a natural state, your in. Chunking, is another great way to fish. Here again, drop chunks over side, try floating a hook bait, among the chunks as they are sinking and floating away, very natural. Might have to add a piece of foam in hook bait, to slow, and keep it among the chunks sinking. Keep repeating, it pays off.