Japanese Horse Mackerel
What is Aji (Japanese Horse Mackerel)?
The Japanese umbrella term for a group of fishes from the subfamily of jacks and pompanos is “aji”. In Japan, especially in the culinary context, the term usually refers to the Japanese horse mackerel (maaji). Although other important fish also include the term "aji" in their name, such as white trevally (shimaaji), the use of the term aji sushi is usually applied only to Jack mackerels or saurels (lat. Trachurus spp.) and mackerel scads (lat. Decapterus spp.).
Aji as Ingredient for Sushi or Sashimi
Aji is one of the most important representatives of sushi ingredients prepared with the shiny silver skin (hikarimono). The meat of aji is pink and firm. It is also juicy, rich in fat and has a strong characteristic taste. Like other silver-skinned fish, ajj is particularly tasty after salting and marinating in vinegar (sujime-method, 酢じめ). Marinating not only preserves and absorbs strong flavours, but also serves to enrich aromas and reduce the “fishy” taste. Contrary to popular belief, soaking in a salt or vinegar solution does not sufficiently kill any parasites that may be present.
While the currently popular seki aji ... is coming to the tsukiji market, I want to make nigiri with aji (maaji), which is much smaller and tastes lighter.
- Jiro Ono, Sushi Chef [Satomi, 2016]
In high scale sushi restaurants, such as the famous Sukiyabashi Jiro in Tokyo by Jiro Ono, raw aji is also preferred. According to Jiro's statements, raw aji is not only more difficult to process, but also makes higher demands on quality and freshness than if aji was marinated in sujime. It should be noted that the meat of aji can spoil very quickly due to its high enzyme content [Satomi, 2016].
Usually aji nigiri is garnished with freshly grated ginger (oroshi shōga, おろし生姜) and finely chopped spring onion (negi, ネギ), together this creates an amazingly successful combination of flavours and is more suitable than Japanese horseradish (wasabi, ワサビ). This combination blends wonderfully with vinegared sushi rice. Soy sauce should only be used sparingly for glazing. The meat of aji is rich in omega-3 fatty acids and vitamins B2, B3, B6 and B12.
The best season is generally late spring to early autumn, not immediately before and after the spawning season of the respective population. Due to the global distribution in the northern and southern hemisphere and the logistic availability, aji is also available all year round in good quality.
Aji in Japan
In Japan, aji is an important ingredient in many dishes. Besides being used for sushi and sashimi, horse mackerel are often grilled, simmered, or fried. The fact that Aji is highly appreciated as an ingredient in Japan is reflected by the fact that the Japanese word "aji" also means “taste” in Japanese.
Aji from the Strait of Bungo
In Japan, Japanese horse mackerel are called seki aji if their fishing area is in the Strait of Bungo (bungosuidō, 豊後水道). Only specimens caught off the coasts of Saganoseki City may be called seki aji. The meat is characterized by its balanced amount of fat and firm flesh. They are particularly popular in upscale sushi restaurants and are traded at correspondingly high prices.
Characteristics & Ecology of Aji (Japanese Horse Mackerel)
Many species categorized by the Japanese as belonging to the group of aji are native to tropical and temperate waters of the world. The most relevant species of this group for the preparation of sushi is the Japanese horse mackerel (maaji), whose range extends from Hokkaido to the South China Sea. In contrast, the most economically important species is the Chilean jack mackerel. This is also used in Japan, along with related species from the North Atlantic and South Pacific, as a substitute (daiyogyo, 代用魚) for the preparation of aji sushi. The closely related amberstripe scad (muroaji) is found primarily in tropical and subtropical waters and is also considered an important seafood in Japan.
Beast Season for Aji
Further information on the author can be found in the section on image credits.
Video about Aji
Distribution Area of Aji
Source: Kaschner, K., Kesner-Reyes, K., Garilao, C., Segschneider, J., Rius-Barile, J. Rees, T., & Froese, R. (2019, October). AquaMaps: Predicted range maps for aquatic species. Retrieved from https://www.aquamaps.org. Scarponi, P., G. Coro, and P. Pagano. A collection of Aquamaps native layers in NetCDF format. Data in brief 17 (2018): 292-296.
Warnings Regarding Aji Sushi or Sashimi
- SCOMBROTOXIN: The naturally have high levels of enzymes causes the meat to let it rot quickly. It is therefore essential to maintain an appropriate cold chain until prompt processing. Histamine is not destroyed by normal cooking temperatures, so even properly cooked fish can still result in poisoning. [FDA, 2020]
- PARASITES: The meat, especially that of wild-caught specimens, may be infested with parasites that cause infectious diseases. Infection can be avoided if the raw meat has been adequately frozen. Pickling and soaking in salt or vinegar solution is not sufficient to eliminate the parasites. If the product has been farmed, only raw unprocessed seafood from production facilities whose products are approved for raw consumption should be consumed. [FDA, 2020]
Species of Aji
The following species are regarded as authentic. Either historically, according to the area of distribution or according to the common practice in today's gastronomy:
Common Names, Scientific Name
Japanese horse mackerel, Japanese jack mackerel, Japanese scad
The following species can be considered subsitutes. Either on the basis of genetic relationship or because they are similar in taste or appearance:
Common Names, Scientific Name
Chilean jack mackerel, Inca scad, Oceanic Peruvian jack mackerel
amberstripe scad, mackerel scad, mackerel scad
European horse mackerel, atlantic horse mackerel, cape horse mackerel
References & Further Reading
- [Fujiwara, 2013]: 藤原昌高. すし図鑑 (engl. Sushi Picture Book). Mainabi Shuppan (マイナビ出版). 2013.
- [Satomi, 2016]: Shinzo Satomi. Sukiyabashi Jiro. Vertical Inc., New York. 2016.
- [Tomiyama, 1972]: Tetuo Tomiyama, Zen Nihon Suisan Shashin Shiryō Kyōkai,. Fisheries in Japan: Jacks and pompanos, Vol. 8: Fisheries in Japan, Zen Nihon Suisan Shashin. Japan Marine Products Photo Materials Association, Tokyo. 1972.