Distinguishing the Yellowfin Tuna from the Blackfin or Bigeye is sometimes difficult as many visual features are similar. Finlets of the Yellowfin are yellow, trimmed in black. Gold stripe along side. Light underside usually shows spots and/or wavy lines. Second dorsal and anal fins of very large individuals are elongated and lunate - a feature not found on any other Tuna. Dorsal spines (total): 11 - 14; Dorsal soft rays (total): 12-16; Anal spines: 0; Anal soft rays: 11 - 16; Vertebrae: 39. Fish with very long second dorsal fin and anal fin, which in some may reach well over 20% of the FL. The pectoral fin is moderately long, usually reaching beyond the second dorsal fin origin but not beyond the end of its base. Color is black metallic dark blue changing through yellow to silver on the belly. The belly frequently has about 20 broken, nearly vertical lines. The dorsal and anal fins and finlets are bright yellow.Yellowfin Tuna occur worldwide in deep, warm temperate oceanic waters. It is both pelagic and seasonally migratory, but has been known to come fairly close to shore. Yellowfin are a mid-sized tuna species and are distinguished, as their name suggests by their yellow fins. They are bigger than Albacore and skipjack but smaller than the famed bluefin. Yellowfin tuna grow fairly fast, up to 400 pounds, and have a somewhat short life span of about 7 years. Most yellowfin tuna are able to reproduce when they reach age 2 or 3. In the western Atlantic, they spawn from May to August in the Gulf of Mexico and from July to November in the southeastern Caribbean. In the eastern Atlantic Ocean, they spawn from October to March in the Gulf of Guinea and from April to June off Senegal. Females spawn about once every 3 days during the spawning season. They produce an average of 1 million to 4 million eggs each time they spawn. Yellowfin tuna feed near the top of the food chain on fish, squid, and crustaceans. They are also prey for top predators such as sharks and large fish. Yellowfin tuna are a torpedo-shaped fish. They’re metallic dark blue on the back and upper sides, and change from yellow to silver on the belly. True to their name, their dorsal and anal fins and finlets are bright yellow. Different species of tunas can be difficult to distinguish – they’re similar in shape and are often caught together. Yellowfin tuna can be distinguished from other tunas by its long, bright-yellow dorsal fin and a yellow strip down its side. It’s also more slender than bluefin tuna.