Akaio - Red O

...Also, yellowtails are called yellowtails because their tails and other fins are yellow, but this species is brownish and not yellow. Its body color is also slightly reddish, and it is called Akaio in Hokuriku, and Akahana, Akabana, and Akabara in Kansai, Shikoku, and Kyushu. Amberjack is a name used around Tokyo, and the prevailing theory is that it is called Mahachi because the black band that runs diagonally across the eye looks like the figure eight when the head is viewed from the back.

*Some of the terminology that mentions "Akaio" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…また，ブリ類はyellowtailと呼ばれるように尾びれをはじめ各ひれが黄色いが，本種は褐色がかっていて黄色くない。体色もやや赤みがかっていて，北陸でアカイオ，関西，四国，九州でアカハナ，アカバナ，アカバラなどと呼ばれる。カンパチは東京付近の呼名で，眼を斜めに横切る黒帯が，頭を背側から見ると八の字に見えるので間八と呼ばれるという説が有力。…

※「アカイオ」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報