Autumn, the most beautiful season in Japan, brings with it great sushi and Japanese sake. In order to start the season off right, I'd like to introduce the most popular autumnal fish in Japan. First one is called Katsuo, or Bonito, other names would be Skipjack or Bonita.
The Katsuo is in season twice a year. During spring the first Katsuo are leaner and more flavorsome. Around September returning Katsuo appear. The fish are fatter and are much heavier than the spring Katsuo. I recommend visiting Kochi Prefecture, Kochi is on the southern coast of Shikoku if you want to eat absolutely the best Katsuo. But, even if you are not able to travel that far, then local supermarkets around Japan should start selling them around mid September. If you are around Shizuoka I recommend visiting this site called Shizuoka Gourmet which is an amazing site packed full of useful information about Japanese food, and nihonshu ( Japanese rice brew).
Another big name fish for Autumn would be the Kohada, or Gizzard Shad. I think a lot of Western gourmands overlook the sublime and mellow texture of this fish. People who eat this fish tend to admire its brilliant silver skin and overall good taste. Personally, I think the fish is underrated and should be pushed more because of its visual appeal.
And then, how can I forget Saba or Japanese Mackerel. I think in Kanagawa Prefecture, Saba is the most popular local specialty. Saba is usually marinated in vinegar and then served up as a sushi. The best saba for me is when the sushi rice is nice and warm, and the saba is fresh as it just melts in your mouth and blends perfectly.
Ikura, or salmon roe have high nutritional content, but is also high in salt which may not be good for people with high blood pressure. Nevertheless, it's an acquired taste that some people like myself don't particularly prefer because of its high salt content. Other then that, it's a fairly good seafood if you don't mind the little eggs bursting your mouth.
So the next time you stop through your local sushi restaurant or kaiten sushi, remember to eat these fish first. Cheers!