Yellowfin Tuna, Thunnus albacares
The yellowfin tuna is found in deep off-shore water distributed worldwide in both tropical and subtropical oceans, ranging to depths of 330 ft. The yellowfin can dive to 3,500 feet or more, but generally school in depths 246 feet or less. Although the yellow fin is a deep water fish it will occasionally come to shallower water to feed when water conditions are suitable and food is abundant.
Being one of the larger species of tuna the yellowfin can weigh over 400 lbs. and reach a length of 8 feet. It has a second set of dorsal (top) and anal (bottom) fins, with a row of smaller fins between them and the tail, all of these fins are yellow in color including the tail, therefore called the yellowfin. Also the second set of fins is quite long in adults and can curve back almost to the tail in the larger of the species. The pectoral fins (side fins) are also long and curve back toward the tail. The body of the yellowfin is a dark blue metallic with a silver belly with 20 vertical lines.
Yellowfin tuna eat, squid, crustaceans, and smaller fish, including other species of tuna. The body design of the yellowfin enables it to pursue and feed on even the fastest specimens, including mackerel, sardines, anchovies, and flying fish.
Even with the size and speed of this species it is prey for the toothed whale, the mako and great white shark, and blue and black marlin; however, the tuna industry is the main predator of the yellowfin.
Spawning occurs in the summer months when the water surface temperatures reach 80 degrees F. When the yellowfin reach maturity at around three years of age the female begin spawning every day or two, this will continue for several months laying her eggs that will float on the water’s surface.
Yellowfin are capable of migrating more than 600 miles in a 12 month period, but a clear migratory pattern has not been established off the west coast of America.
While the yellowfin tuna is highly regarded as a food fish, it is also on the endangered list as near threatened. It is fished as a sport for its fighting ability when taken on a rod and reel. Commercially means of capture are artisanal fishing (low technology), longline fishing (deep water capture using a long line with multiple baited hooks), and purse seine (using a net that closes as it is pulled up), this one is the most commonly used type for commercial taking of the tuna.
Image Caption: Yellowfin tuna surfacing and diving back into the water. Credit: NOAA FishWatch/Wikipedia