Hikarimono (Silver-skinned fish) includes horse mackerel, mackerel, sardines, sillago, and gizzard shad, generally referred to as blue-backed fish. Hikarimono all have high-fat content. It is approximately 7% in gizzard shad and horse mackerel. It is about 16% in mackerel. The taste is heavy. Many of the fish in this category lose their freshness quickly, so the preparations differ greatly from restaurant to restaurant. They say that you can tell how well a restaurant is doing by which Hikarimono they serve. This may be why many restaurants make sure to work hard on their Hikarimono.
Tachiuo really does look like a sword from the outside, so it seems like it should be classified as Hikarimono, but it’s actually Shiromi. In the sushi restaurant sector, Hikarimono refers to sushi toppings for which Sujime is used in the preparations. Furthermore, there are chefs who classify Shima aji as Hikarimono when the silver skin is left on, and Shiromi when the skin is removed.