Yellowfin tuna have yellow sides, blue backs, silver bellies and can weigh up to 450 pounds, whereas Pacific yellowtail have yellow stripes across their bodies, a yellow tail and weigh between 10 and 20 pounds when caught on a line. Yellowtail, or Seriola lalandi, is not a species of tuna and generally weighs less than a yellowfin, or Thunnus albacares.
Yellowtail are considered a delicacy in Japanese cuisine as an ingredient for sushi. These fish, called hamachi in Japan, are grown on farms and exported to other countries. As of August 2014, the longest yellowtail ever caught was more than 8 feet long, and the largest specimen ever recorded weighed more than 213 pounds. Yellowtail live in subtropical waters all over the world. Yellowtail feed on mackerel, sardines, anchovies, crab and squid.
Yellowfin are actual tuna found in all three oceans of the world. These fish swim with other tuna species, and they associate with dolphins. As of August 2014, the longest yellowfin recorded was 7.8 feet and was caught in Florida. The heaviest yellowfin recorded was 441 pounds. The largest school of yellowfin is found in the eastern Pacific Ocean from Chile to California. Yellowfin are a top predator in the ocean food chain.