i have eaten mack tuna up to 6kg and i cut them into portions and marinate in 1/2 cup olive oil, 1/2 cup lemon juice and some garlics for 20 mintues and then throw them on the bbq for a few seconds on each side so they are still red in the middle, i love it. fish cakes is also great. but i have caught more snapper on mack tuna then i have had feeds.