To keep the Tuna in best condition be careful how you handle it.
**Always gaff in head to avoid puncturing flesh which will ruin the meat around the puncture for a good distance.
At the very minimum tuna must be killed and bled immediately to prevent build up of lactic acid and to prevent the temperature of the blood from rising.
STEP 1: If possible, club the fish sharply on the top of the head between the eyes to stun it and prevent the thrashing which bruises the meat.
STEP 2: By running your thumb along the top of the head of the tuna you will feel a soft spot usually directly above the eyes. Insert a sharp spike or knife into this soft spot at an angle of 45