Crabs are great baits for tuna. Use lively crabs or cut pieces of crab and you can catch a variety of tuna.
Pilchards are one of the best baits for a variety of saltwater game fish and tuna are no different. Get a lively pilchard in front of a hungry tuna and you will catch some fish.
Cut squid can work great for tuna. Cut them in longer strips and you will have a lot of success fishing for tuna.
Mackerel might be the best tuna bait. Tuna will school up and feed on schools of smaller mackerel. Get some lively mackerel and you can do very well for tuna.