Iwashi Sushi

In Japan the collective term iwashi (鰯・鰛・鰮) refers to a group of fishes beloging to the families of Clupeidae, Dussumieriidae and Engraulidae. Within this generic term, a distinction is made between three types. Those types are the pacific pilchards or sardines, round herrings and anchovies. These three groups are caught in large quantities and are important not only for fresh fish but also for the processing industry.

The fish of the iwashi group are considered fragile, which must be processed carefully and quickly. Since its meat decomposes rapidly, it develops an unpleasant odor early after being caught and is therefore only available in limited quantities in sushi or sashimi quality. To maintain freshness iwashi is either soaked in 3 to 5 percent salt water or previously sprinkled with salt and then placed in a mixture of ice water and vinegar. The osmotic effect of the salt solution has a slightly preservative effect, reduces the odor and maintains the shiny skin surface characteristic of iwashi.

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With plump in-season iwashi, the fatty layer in between the skin and the flesh is amazingly thick. Despite that, it neither smells fishy nor tastes greasy.

- Jiro Ono, Sushi Chef [Satomi, 2016]

Ginger and green onions are suitable as a garnish. Besides the taste component, ginger also has a neutralizing effect on the smell. Especially fresh specimens harmonize very well with wasabi alone. In upscale sushi restaurants, ginger and spring onions are sometimes pressed into a paste, refined individually and placed on top of the nigiri that is coated with soy sauce. If iwashi is prepared as sashimi, soy sauce mixed with ginger is very suitable.

The spawning times of maiwashi depend on the region and population, therefore no exact season can be determined for sardines from the group of ma iwashi. In Japan the months from June to October are traditionally considered to be the tastiest time of year for Japanese sardines. The spawning season of the european sardine (yōroppa ma-iwashi) also varies considerably by region and population, with the main fishing season beginning in late spring and ending in late summer. Iwashi caught between spring and summer are also considered particularly tasty and are called baiu iwashi (rainy season) or nyuubai iwashi (beginning of the rainy season). Urume iwashi is caught all year round, but it is said that the best season is from winter to early spring, when the fish have become fattier. Katakuchi iwashi migrates from the East China Sea to the coastal region of Taiwan to spawn in late winter and early spring. Therefore summer is considered the best season for katakuchi iwashi.

In Japan, October 4 has been the official sardine day since 1985 (イワシの日). The day was created by the Iwashi Promotion Association (いわし普及協会) with the aim of encouraging the acceptance of sardines as a cheap and tasty fish. In Japanese, October 4th is written as 10月4日, resulting in a pun that reads iwashi (1 → い [i], 0 → わ [wa], 4 → し [shi]) [Kase, 2009].

The most common iwashi species found on Japanese dining tables is Japanese sardine (maiwashi), which also serves as a eponym for its associated species. Of all iwashi species, it is most commonly used for the preparation of sushi or sashimi.

The Japanese sardine is a submember of the species Sardinops sagax. Accordingly, all representatives of this species are understood as maiwashi, literally “genuine“ or “true sardine“. The population of maiwashi is divided into five different subspecies, chiri-maiwashi in the waters around Chile, cariforunia-maiwashi in California, maiwashi in Japan, ōsutoraria-maiwashi in Australia and minami-afurika-maiwashi around Africa. The European sardine, because of its similarity, especially in taste, is also culinary counted to maiwashi and is called yōroppa-maiwashi.

The Pacific sardine usually occurs within large schools in coast-proximity. Young animals feed on zooplankton, adult animals mainly on phytoplankton.

The taste of the red-eye round herring (urumeiwashi) is the most distinctive of all sardines belonging to the group of iwashi. Urumeiwashi is therefore often used for the preparation of sushi or sashimi. It is caught in much smaller quantities than ma iwashi and katakuchiiwashi. Therefore, urumeiwashi appears less frequently at markets and is therefore rarely found in sushi restaurants. Furthermore, urumeiwashi, like all fishes of the iwashi group, is very sensitive and must be processed quickly after the catch. Urumeiwashi is often dried and prepared on a skewer and offered as urumeiwashi no mezashi (ウルメイワシのメザシ).

Urumeiwashi lives in tropical and temperate waters not only in Japan but all over the world. They swim in shoals near the sea surface and feed mainly on plankton.

The Japanese anchovy (katakuchi iwashi) is the smallest representative of iwashi fishes with an average length of 10 cm. Only the freshest specimens are suitable as sashimi and are highly appreciated for their good taste. A large part of the landed katakuchiiwashi are industrially processed as canned or dried fish. Juveniles or the immature fish fry are prepared into shirasu (しらす) and chirimenjako (ちりめんじゃこ).

In the years from 2000 to 2018, the Japanese sardine accounted for an average of 21 percent of the global catch of the ma iwashi group. The share of the european sardine was 54 percent. Ma iwashi is mainly used for the production of processed products up to the production of fishmeal, only a small percentage is used as fresh fish.

Gallery

Distribution Area of Iwashi

1. 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]
2. 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. [Audicana et al., 2002]

Image Credits

1. T.Tseng. Iwashi, Kyo Sushi, Juárez, CDMX Mexico. flickr.com. License: Attribution 2.0 Generic (CC BY 2.0). Changes made: image quality, brightness, contrast, colour matching, sharpening, cropping.

2. takaokun. IMG_0729, Iwashi Nigiri. flickr.com. License: Attribution 2.0 Generic (CC BY 2.0). Changes made: image quality, brightness, contrast, colour matching, sharpening, cropping.

3. D. Schilder. Nishi Iwashi Sushi. License: copyrighted ©.