Yellow fin tuna fish prefer to swim 10 or more miles off shore at depths of 300 to 600 feet. The yellow fin is a solitary fish, but feeding typically occurs in schools. It is common for extra scraps from feeding fish to go uneaten during large feeding circles, which can attract seabirds and other sky predators. Always look for water disturbance and circling birds as an indicator that tuna fish are feeding in the area. Tuna typically swim closer to the surface during summer and at lower depths during winter.
Get your lines in the water early during low light when fishing for bluefin tuna, and always stack your lines. For example, tie one bird, one or two vinyl squids and a green machine daisy chain at the center line and stack each lure with a snap at the rear. Combine with triple cedar plugs, and troll at 5 to 9 miles per hour in areas where you have spotted tuna. Black, blue and white plugs work best on a long rig when fishing for bluefin, and natural plugs are best for flatlines. Other effective line combinations include sets of black, blue and white, red and white and natural. Nighttime fishing is also an option. Tuna bite more frequently in low light.
Chumming is an alternative to line fishing and trolling. Larger tuna fish are especially receptive to chumming. Attach chum (salmon) to the stern of your boat to attract baitfish and tuna. Tuna fishermen also swear by ground menhaden or mossbunker---a fish that averages about one foot in length and produces a large amount of oil. Chumming requires that you attract baitfish and not overfeed them, so limit how must chum you use. Target choppy areas where water disturbance is high and visibility is low.