The term 'kind of tuna' can refer to two different species of tuna, BIGEYE (6 letters) and BLUEFIN (7 letters). BIGEYE tuna is a large, deep-water fish that is found in tropical and temperate waters around the world. It is a highly sought-after species for commercial and recreational fishing due to its high fat content and flavor. BLUEFIN tuna is a large, migratory species that is found in the Atlantic, Pacific, and Indian Oceans. It is one of the most valuable species of tuna and is highly prized for its fatty flesh.