Animals are all the same, they leave sign showing where they are and have been.
Once you get to the likely spots, you need to find these signs and track them down. Elk/Deer leave foot prints and little round pellets to track them. Tuna leave tail tracks and a though the little round pellets sink, the urine stays near the surface. We often sample the water for PH. When we get a lower than average reading we know he tuna have been there or are there. The last couple trips we didnt have any PH strips left and we just tasted the water. You will know when the urine count is high.
You need to keep an eye in the water for the tail tracks. When you see patterns of little swirls in the water about 4 to 6 inchs apart, you are hot on ones trail or shall we say tail. As the tail moves side to side these swirls are created. I have one guy I regularly crew with who can track a butterflys shadow across solid rock up to 3 days old. I think he is part apache, but he claims he is from ireland as he likes his alcohol. The guy can spot tail swirls in the water 50 feet from the boat.
Birds are always a good sign, but cant be counted on. We have caught a lot of tuna with no birds in sight.
If you do see birds diving there are usually tuna under them pushing the bait up.
We have only had mild success with calling tuna to the boat. Sort of a pied piper approach to tuna fishing. I cant explain it, but listening to polka at a really loud volume, has shown some promise in bringing tuna right up to the boat. Our next trip we hope to take one with a bow and arrow and we will be using polka to draw them in.
Tuna only have two things on their mind, eating and shall we say....."the rutt". Most people use the eating technique to catch their tuna by putting bait in the water and using lures that simulate something they might eat. But capitalizing on their desire to make little tuna can be used also. It would be nice if tuna bugled like elk, and if they do it is on a frequency we havent found yet or it gets drowned out in all the water. Female tuna urine in estrus has been very effective for us this year. You only catch males, but by working a piece of water and continually putting some urine in estrus in the water you can draw a lot of males into the area. They get busy looking for receptive girls and dont do a whole lot of thinking. These grouped up fish are easier to catch in triples and quads.
The last thing we have had success with this year is decoys. Lifelike tuna decoys are made from a lightweight neutral bouyant material. We place 15 or 20 of these decoys behind the boat in a tight cluster. This draws other fish into the spread and we can catch them.