Longtails are a painful species to target on cast lures at the best of times as they very rarely hold in 1 spot for very long, and are extremely boat shy. Even when there are masses of bait, they dont hang around and ball it up, they make 1 quick messy attack and move along.
Blind casting is very inefficient. Best bet is to find masses of garfish and wait for the tuna to blow up on them.