The English term for Hamachi is “yellowtail”, and Kanpachi is “amberjack”. But because yellowtail can also be called “Japanese amberjack”, overseas sushi diners sometimes think they’re the same fish.
Though they’re both members of the “jack” family, “yellowtail”, “Buri” or “Hamachi” are names for the species Seriola quinqueradiata. “Amberjack” or “Kanpachi” is the species Seriola dumerili, which is less fatty and not as much exported from Japan. Yellowtails are farmed commercially in Japan, Australia, and now the US. Approximately, 90 percent of farmed fish in Japan for export is yellowtail.
The name “Hamachi” and “Buri” can also be confusing. Traditionally, there were different names for wild yellowtail at each stage in their development as they grow from a fry to an adult. There were also differences in terminology between Tokyo and Osaka. Buri (yellowtail) begin life as Wakashi (in Osaka Tsubasu), become Inada (in Osaka Hamachi), then, at 3 years become Warasa (in Osaka Mejiro) and finally the full-grown Buri. To make things confusing, farmed yellowtails were given the name hamachi, although the name was already used in Osaka to name the younger yellowtail.
It is often confused that hamachi is a name for young yellowtail in Osaka, however, most Japanese would tell you that hamachi is the farmed version of yellowtail.
Since the farmed Hamachi are raised in nets immersed in the sea, they do not get as much exercise as wild yellowtail, and become fatty, with soft muscles and light colored flesh. Wild Hamachi is smaller and darker, with firmer flesh.
Some Japanese prefer the firmer texture of wild Hamachi, while others like the fattier farmed product. Farmed Kanpachi is springier, less fatty, and somewhat more flavorful than Hamachi.
Farmed Hamachi is available year-round, and is thus more suitable as an export, while the wild Buri is mainly a seasonal domestic item in Japan. (Floro Mercene)