I get asked this question just about daily. And in fact, the best time to go is when you can go.
We catch tuna all year long here in Venice. That is why we call it the "Tuna Capital of the World". Most of our customers prefer the summer season. The seas are more likely to be calm and we have the opportunity of catching mahi, wahoo and snapper. Calmer conditions allow us to run faster and get to the grounds sooner as well. It is an ideal situation for most anglers.
But if you are solely interested in Tuna, there really is no better time than the present for you go fishing. Granted we get bigger fish in the winter, however an 80 pound summer tuna fish is no slouch! Plenty of meat for the coolers and a hell of a fight. In fact, sometimes even our 40 pound fish act like much bigger ones and put a hurting on our angler arms.
I recommend you don't get so caught up in the whole "winter are bigger fish in Venice" thing. Because you have to worry about weather then and there are no guarantees in fishing.
So if you are looking to go Tuna fishing, I highly recommend you book as far in advance as you can. We do still have a few dates left here in June and some in July. Let's get out there and get tight!
Tight Lines,
Captain Chandler