Bluefin tuna are the largest of the tunas. They have a long pointed head and small eyes. Bluefin tuna have two dorsal fins with a small space between them and short pectorial fins. Their anal fin begins far behind the second dorsal fin and they have three keels on their caudal peduncle. Bluefin tuna have a metallic blue color on the top half of their bodies and silver from the middle of their sides down to the bottom. Their first dorsal fin is yellow or blue and their second is red or brown.  Their anal fin and finlets are yellow edged with black.  Their central caudal keel is black. Bluefin tuna are usually between .5 and 2.0 meters in length. They weigh on average between 136 kg and 680 kg

Range mass: 136 to 680 kg.

Average mass: 250 kg.

Range length: .5 to 4.5 m.

Average length: 2 m.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: sexes alike