1. Which Japanese Fish Change Their Names, and What Does That Mean?
A shusse-uo is a fish whose name changes with its growth, until it gets its "real" name, or a special name, as an adult. A large Japanese encyclopedia names the best-known examples as the yellowtail, the grey mullet and the Japanese sea bass [2]. It also says why such fish are special: between baby and adult, their way of life changes a great deal, and so do the fishing methods used to catch them and the price they sell for [2]. In other words, a small yellowtail and a big one are not just the same fish at different sizes to the people who catch and cook them.
The sources show that one fish can pass through several names as it grows. The next section looks at the best-known case.
2. How Does Yellowtail Go From Wakashi to Buri, and Why Do the Names Change by Region?
Chiba Prefecture, which sits next to Tokyo, explains that yellowtail change names as they grow: wakashi, inada, warasa, buri in the Kanto region around Tokyo, but tsubasu, hamachi, mejiro, buri in the Kansai region around Osaka [1]. So these two lists share the first and last names, and the middle ones move around.
The encyclopedia gives even more variety. Tiny yellowtail of about 3 to 7 cm are called mojako. After that, Tokyo uses wakashi, inada, warasa and buri. Toyama Prefecture on the Sea of Japan coast uses tsubaeso, fukuragi and buri. Hyogo Prefecture uses tsubasu, mejiro, ninengo and sannengo. Kochi Prefecture uses mojako, hamachi, buri and oinada [2]. The same source warns that the sizes are not strict, and that names vary somewhat from place to place. It adds that the names were once quite different between regions and social classes, but that fish sold widely across the country slowly became more uniform [2].
The practical lesson: do not read a name as "exactly this many centimeters." It is a rough label that depends on where you are. But why did anyone create so many labels?
3. Why Would People Give One Fish So Many Names?
The sources point to a few connected reasons, and none of them claims to be the only one.
Taste changes as the fish grows. A Japanese encyclopedia says the names change partly because flavor changes with growth [3]. Chiba Prefecture gives a concrete example. Yellowtail that spread north in summer begin to move south in early autumn, and in winter they reach the time of "kan-buri" (winter yellowtail), the period when the fish is richest in fat. Even so, the smaller inada that appear in summer are less fatty but have a light, clean taste of their own [1]. So a shopper who wants a rich fish and a shopper who wants a light one are, in a sense, looking for different names.
Catching and selling differ. As noted above, the way of catching and the market value change as the fish grows [2].
People used each stage. A guide from a Japanese government office, written about mullet in the lower Tone River near Tokyo, makes the point directly: having a name for each growth stage means the fish was used at each stage [4]. Its examples include a regional dish of small mullet stuffed with miso paste and grilled, sashimi and "arai" (thin slices rinsed in cold water) from larger fish, and karasumi, salted and dried mullet roe. The guide adds a thought of its own: like the goby, the mullet may be one of the most "everyday" fish [4].
These explanations are a reading of the evidence, not a proof. But together they fit one picture: a name is useful when it tells you what you will catch, cook or taste.
4. How Do Sea Bass and Mullet Use the Same Idea?
The Japanese sea bass follows a similar pattern. According to a Japanese encyclopedia, in the Kanto region a one-year-old of about 25 cm is a seigo, a two- or three-year-old of about 35 cm is a fukko, and a fish of about 60 cm (four years or older) is a suzuki. In Kansai the sequence is seigo, hane, suzuki, and in the Chubu region it is seigo, madaka, suzuki [5]. Again, the first and last names match and the middle name depends on the place.
The mullet has the longest staircase. The Tone River guide lists, for Kanto, oboko, inakko, subashiri, ina, bora, todo, and for Kansai, haku, oboko, subashiri, ina, bora, todo [4]. The encyclopedia puts a "haku" at about 3 cm, an "ina" at about 25 cm (around one year old), a "bora" at 30 to 50 cm (two to four years), and a "todo" for the oldest and largest [6].
Sources disagree a little. One encyclopedia defines todo as a fish of five years or more, while another uses 50 cm or more [6][2]. That again shows that the sizes are rough guides. Mullet is also a fish whose last name leads to something surprising.
5. Which Everyday Japanese Words Came From Mullet Names?
Here the fish name escapes the fish counter. A dictionary gives todo as "the most grown-up stage of the mullet," and also as a short form of the adverb todo no tsumari, which means "in the end" or "after all" [7]. The big Japanese encyclopedia says that the names of the mullet's growth stages gave rise to two everyday expressions: todo no tsumari ("in the end") and inase, an old word for a dashing, stylish young person (from ina) [2].
The idea behind todo no tsumari is neat: a fish goes through many names, and the last one it reaches is todo. One of the dictionary's old examples is a short comic verse printed in 1830, which plays on the same thing: "The todo is a mullet; in the end, what will it become?" [7]. Word origins are often debated, so it is safest to say that this link is a widely given explanation, not a closed case.
Why does this matter for our question? If a fish had four or six names that ordinary people knew, its names could become raw material for everyday speech. This last point is my own inference, not something the sources say.
6. How Can You Check Fish Names for Yourself?
If you visit a Japanese grocery store or fish market, or a sushi restaurant that lists fish names in Japanese, look for hamachi or buri and notice which one appears. You can also look at labels in a Japanese supermarket's seafood section and ask the staff whether a name changes with size. They may know a local name you will not find in any book. If you cannot visit, search for the Chiba Prefecture yellowtail page and the Tone River mullet guide listed below, and compare their lists with the ones here. Where do the names agree? Where do they differ? The next question to chase is how fish names work in other languages, and whether your own region has a name that changes as a fish grows.