Ahi Tuna vs Bluefin Tuna: Key Differences Explained

Yellowfin tuna out in the open ocean in crystal clear blue water
© Al McGlashan/Shutterstock.com

Written by Hannah Ward

Published: August 22, 2022

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Tuna are some of the most incredibly stunning and powerful fish in the world. With their torpedo-shaped bodies built for speed, some species can even reach 47mph – making them hugely popular with sport fishing. However, they are incredibly popular with commercial fishermen, as their meat is highly sought after worldwide. Two of the best-known types of tuna are bluefin tuna and ahi tuna, and at first glance, they can look extremely similar. However, they are very different fish, and luckily, there are some key differences that we can use to tell them apart. So join us as we discover everything you need to know about ahi tuna vs bluefin tuna!

Comparing Bluefin Tuna vs Ahi Tuna

Southern bluefins can reach 8ft 2in and weigh up to 570 pounds, while Pacific blue fins can reach 9.8 feet long and weigh up to 990 pounds.

Ahi tuna and bluefin tuna are not just single species of tuna. Instead, ahi tuna is the common name given to yellowfin (Thunnus albacares) and bigeye tuna (Thunnus obesus). Additionally, there are three species of bluefin tuna – Atlantic (Thunnus thynnus), Southern (Thunnus maccoyii), and Pacific (Thunnus orientalis).

Bluefin TunaAhi Tuna
LocationPacific bluefin – northern Pacific, migrates to southern
Atlantic bluefin – western and eastern Atlantic, Mediterranean Sea
Southern bluefin – southern hemisphere waters of all oceans
All tropical, sub-tropical, and temperate oceans
Water DepthUp to 3,300 feetTypically up to 1,640 feet
SizeLength – up to 12 feet
Weight – up to 1,500 pounds
Length – up to 8 feet
Weight – up to approx 440 pounds
AppearanceHeavy body, dark blue back, silver or white lower sides and belly. White lines and spots on underside. Second dorsal fin dark colored. Blue tail finBlue back and upper sides, white belly and lower sides. Yellow lateral line above pectoral fins. Yellow anal fins and second dorsal. Finlets and tail fin largely yellow
Pectoral FinsShort – ends before the second dorsal finLong – often extend beyond second dorsal fin
DietFish (mackerel, herring, sardines, anchovies, smaller tuna), jellyfish, octopus, crabs, squid, crustaceans, eelsFish, crustaceans, squid
PredatorsOrcas, pilot whales, sharksSharks (especially great whites & makos), whales, larger tuna, marlin, wahoo, billfish
Lifespan40 years15 years (bigeye), 7 years (yellowfin)

The 4 Key Differences Between Ahi Tuna and Bluefin Tuna

Ahi Tuna vs Bluefin Tuna: Size

Fastest Water Animals

Bluefin tuna are huge fish and can reach an incredible 1,500 pounds and 12 feet long!

©iStock.com/Whitepointer

One of the most noticeable differences between bluefin and ahi tuna is their size. Ahi tuna can reach up to 8 feet long and 440 pounds, with both yellowfin and bigeye tuna being of a similar size. However, ahi tuna are generally much smaller than bluefin tuna. On average, all three bluefin species are larger than ahi tuna. Southern bluefins can reach 8ft 2in and weigh up to 570 pounds, while Pacific blue fins can reach 9.8 feet long and weigh up to 990 pounds. Although all these tuna are large in their own right, none are as big as the Atlantic bluefin tuna, which reaches an incredible 1,500 pounds and is 12 feet long!

Ahi Tuna vs Bluefin Tuna: Appearance

The easiest way to tell bluefin and ahi tuna apart is by looking at their appearance. Ahi tuna have dark blue backs and upper sides, while their bellies and lower sides are silver to white. They also have a yellow lateral line above the pectoral fins. Their second dorsal fin and anal fins are yellow, while their finlets are either completely yellow or yellow with black edges. Additionally, their tail fin is either completely yellow or a mixture of yellow and grey colors.

As the larger fish, bluefin tuna have extremely thick, robust bodies. Their entire bodies are adapted for power and speed and are shaped like torpedoes. Bluefin tuna have a similar appearance to ahi tuna, with dark blue backs and grey or white lower sides and bellies. However, they have different fin colors. The second dorsal fin on bluefin tuna is dark colored, and their tail fin is dark blue. Bluefin tuna also have many whitish-colored lines and spots on the underside of their bodies.

Ahi Tuna vs Bluefin Tuna: Pectoral Fins

One of the most noticeable differences between ahi tuna and bluefin tuna is the length of their pectoral fins. Ahi tuna have much longer pectoral fins than bluefin tuna. The pectoral fins of ahi tuna reach the area between the two dorsal fins and sometimes beyond, whereas on bluefin tuna, they end well before the second dorsal fin.

Ahi Tuna vs Bluefin Tuna: Water Depth

Yellowfin tuna out in the open ocean in crystal clear blue water

Ahi tuna typically live in water less than 1,600 feet deep, compared to bluefin tuna, which regularly dive to depths of more than 3,000 feet.

©Al McGlashan/Shutterstock.com

One of the most interesting differences between ahi tuna and bluefin tuna is the water depth that they typically live in. Both ahi and bluefin tuna undertake something known as diurnal vertical migration, which is when they migrate up and down the water column every day. During the daytime, they travel down to the deeper and much colder water and back up the water column to the warmer and shallower water at dusk. However, how deep they travel is where the difference lies. Bluefin tuna typically occur in deeper water than ahi tuna. Pacific bluefin tuna typically live in water up to 660 feet but can dive to 1,800 feet, while Southern bluefin tuna migrate as deep as 1,640 feet. However, Atlantic bluefin tuna dive the deepest and can dive up to 3,000 feet!

Ahi tuna typically spend their time in shallower water than bluefin tuna. Bigeye tuna typically migrate between the surface and 1,640 feet deep, while yellowfin tuna usually occur no deeper than 620 feet deep, with less than 330 feet being preferred. However, although they don’t usually dive as deep as bluefin tuna, one ahi tuna (yellowfin) was recorded diving to the incredible depth of 5,223 feet!


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About the Author

Hannah is a writer at A-Z animals where her primary focus is on reptiles, marine life, mammals, and geography. Hannah has been writing and researching animals for four years alongside running her family farm. A resident of the UK, Hannah loves riding horses and creating short stories.

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