Atlantic bluefin tuna nigiri

Atlantic bluefin tuna (Taiseiyou kuro maguro)

【Nigiri sushi: Akami】
At fish markets, “Kuro maguro” generally refers to two types of tuna. One is the Atlantic (or Northern) bluefin tuna, which migrates from the east coast of North America to the Mediterranean Sea, where it spawns. The other is the Pacific bluefin tuna, which migrates across the Pacific Ocean from the waters around Japan to the west coast of North America and spawns in Japanese territorial waters.

These two tunas are closely related species (although some researchers consider them subspecies). They look almost identical, both can live for around 30 years, and can grow to nearly 400 kilograms in size. In practice, the main difference is said to be the shape of the abdominal cavity when the fish is dissected.

Wild Atlantic bluefin tuna from New York, Boston, and Canada are generally regarded as the highest quality, followed by those from Spain, Malta, and Croatia, whose flesh is considered slightly less refined. In particular, Atlantic bluefin tuna caught off Ireland inhabit some of the coldest northern waters. Because of the low water temperatures, the flesh becomes firmer and the tuna develops more fat to protect its internal organs from the cold.

However, most Atlantic bluefin tuna currently distributed in the sushi market is farmed in the Mediterranean Sea. Major producing regions include Spain, Malta, Croatia, and Turkey. In these areas, a method known as tuna ranching is common. Wild juvenile tuna are caught and raised in offshore pens, where they are fed sardines and mackerel to increase their fat content. The resulting rich flavor and high fat content make these tuna especially valued in Japan’s high-end sushi market as otoro (fatty tuna) and chutoro (medium-fatty tuna).

Generally, Atlantic bluefin tuna from the North Atlantic are prized for both their rich fat content and deep umami flavor, and are often priced comparably to wild Pacific bluefin tuna from waters around Japan. At Toyosu Market, the two types of Kuro maguro are not clearly distinguished in everyday market terminology.

【Related contents】
Types of tuna

Types of fishing method

(Added May 18, 2026)