Fish roe
Pollock roe (Tarako)
【Nigiri sushi: Gyoran】
In Japanese coastal waters, three species are distributed along the northern Japanese coast: Madara (Pacific cod), Sukesoudara (Alaska pollock), and Komai (Saffron cod). The ovaries of Madara (Pacific cod) are called “mako,” while those of Komai (Saffron cod) are called “komai-ko.”It's not tarako because it's cod roe (Madara/Tara); it's actually pollock roe (Sukesoudara).
The mentaiko everyone knows comes from the Korean name for Alaska pollock, “明太” (myeongtae), hence the name mentaiko. To elaborate further, tarako is the salted roe of Alaska pollock, while mentaiko is the salted roe of Alaska pollock seasoned with a marinade containing ingredients like chili peppers. In other words, the names are distinguished based on the presence or absence of chili peppers.
However, recently, the common understanding is that tarako refers to the unsalted, non-spicy version, while mentaiko refers to the version seasoned with a spicy marinade, meaning “mentaiko = karashi (spicy) mentaiko” is often how it's used.
Tarako nigiri sushi is made using non-spicy pollock roe. Since tarako is considered a processed product, sushi chefs typically do not use it as a topping. If a sushi chef were to extract the roe from pollock, season it, and marinate it themselves, they might serve it. Generally, it is used as a sushi topping in places like conveyor belt sushi restaurants.
Finally, an important point: sushi chefs who serve each piece individually do not offer tarako. Avoid ordering tarako at sushi restaurants. However, Hokkaido produces 60% of Japan's tarako and has long produced high-quality varieties. Consequently, some sushi restaurants in Hokkaido offer it only during winter.
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