To further increase the shelf life of fish that do not keep well, dishes were created by wrapping sushi in tree leaves. This technique combines salting, fermenting, and wrapping. Kakinoha zushi (persimmon leaf sushi), which is widely known in Nara Prefecture, is an example of this. In Japan, many foods are wrapped in leaves. This is thought to have been done to impart aroma and color, as well as make the food more easily transportable, while certain plant species were also known for their antibacterial (or bactericidal) properties.

Kakinoha zushi is a dish of thinly shaved salted mackerel placed on vinegared rice, then wrapped in astringent persimmon leaves. Recently, salmon, red seabream, conger eel, and similar have been used in addition to mackerel. Tannins found in the fruits and leaves of persimmons have bactericidal properties, and it seems that this dish made use of this action. The neighborhood of Gojo City along the Kinokawa River in Nara Prefecture is also a persimmon growing area, so it is likely that leaves from that area were used. There are multiple theories as to where the mackerel was brought from. One theory is that mackerel caught in the northern part of Wakayama Prefecture was brought in via the Kinokawa River. Another theory is that mackerel caught in Kii-Nagashima, which faces the Kumano Sea off the Kii Peninsula, was brought to the Uda region of Nara Prefecture along another Saba Kaido. Isami Tamura gives more details in Journal of Mackerel Culture (saba no bunka shi; Yuzankaku, 2002), however it is very interesting to note that part of the road runs along the Median Tectonic Line, a major fault line that runs east to west across western Japan. You can also find narezushi both wrapped in and made with leaves. In the Kumano region on the Mie side, a type of narezushi made with ayu sweetfish was eaten for centuries. However, it is believed that declining catches and an abundance of pacific saury from the 1950s led to a gradual switch to narezushi made with pacific saury. This has since been shifting once again to species such as mackerel and barracuda due to poor catches of Pacific saury in more recent times.

Kumano's narezushi is made by fermenting stick-shaped bo-zushi made with soft rice on top of Alpinia japonica leaves for about three weeks. In addition, a large number of leaves from the urajiro fern (Gleichenia japonica) are placed in the vats used to store the sushi. Wakayama also has a variety of narezushi made with leaves, but here, it seems the leaves used are from plants such as the cast iron plant (Aspidistra elatior) and giant cane (Arundo donax) (according to "Our Regional Cuisines," Ministry of Agriculture, Forestry, and Fisheries).

As we are on the topic of mackerel, let's take a look at preserved mackerel dishes from the Sea of Japan side. Heshiko is relatively well known, and perhaps due to effective advertising by specialty food companies, is often introduced as a local dish of Fukui Prefecture. However, since the food is produced across the entire Tango Peninsula region in Kyoto, it should be considered a local dish of the coast along Wakasa Bay. In fact, heshiko is featured on the "Our Regional Cuisines" website for both Fukui and Kyoto Prefectures. Heshiko is made by pickling salted mackerel in rice bran. It has a long storage period and salty taste, with a concentrated umami flavor. Note that fugu-no-ko nukazuke, fermented and aged pufferfish ovaries from Ishikawa Prefecture, is also well known as a dish pickled in rice bran.

Although not a fermented food, there is a dish called barazushi from the Tango region. While mixing ingredients into vinegared rice is also common in other regions, the barazushi served in Tango differs by its use of saba no oboro (minced mackerel). Oboro is prepared by simmering mackerel flesh in a sweet and salty sauce. It used to be made from scratch, however these days, canned mackerel produced in Hachinohe, Aomori Prefecture, is almost always used. Barazushi is a hometown dish that preserves the "taste of home," and it is still made today in individual households on special occasions. There are also specialized restaurants serving the dish.

Mackerel has also long been used as an ingredient in kaburazushi. Kaburazushi is a fermented food made by laying slices of Japanese amberjack between turnips pickled in salt, then letting it ferment. It has been eaten in Ishikawa Prefecture, mainly around Kanazawa City, and the Tonami region of Toyama Prefecture for a long time. In the Nanto region of Toyama Prefecture, mackerel is used instead of Japanese amberjack, however this variation is also called kaburazushi. While Japanese amberjack and mackerel both have soft flesh and bones, it is intriguing to think about why mackerel, which tends to spoil easily, came to be used in the Nanto region, which is located far from the ocean.

These days, nigiri sushi, sashimi, and similar fish dishes are strongly associated with being eaten raw, however these likely constitute a fairly new part of Japan's food culture. In the time before refrigeration and freezing technology, there were no other ways of safely preserving fish for long periods of time other than fermentation and salting. Although many dishes prepared using these methods disappeared after Japan's period of rapid economic growth in the twentieth century, some still remain in different regions. This is the case for the dishes I introduced above, but remnants of fermented fish-eating practices can also be found in several areas outside of the Kinki and Hokuriku regions.

One of the most common of these dishes is shiokara. Shiokara is prepared by salting the entrails and muscles of fresh fish, with squid shiokara in particular found all across Japan. Another well-known variety is made using skipjack tuna entrails. It goes by shuto in Kochi Prefecture and Nishiizu, Shizuoka Prefecture, and watagarasu in Okinawa Prefecture. The "garasu" in watagarasu means shiokara in the Okinawan dialect. There is also another variety using salted baby mottled spinefoot that is called sukugarasu. Sukugarasu is familiar to travelers as it is often seen at traditional pubs, or izakaya, served on top of firm "island" tofu. Other salted seafood dishes known as delicacies include konowata made from sea cucumber intestines, sea squirt shiokara, and bakurai, which is a mixture of konowata and sea squirt shiokara.

Another fermented seafood dish I would like to mention here is kusaya. This is a type of dried food that still remains on the Izu Islands, and the dominant opinion is that it originated on Niijima Island during the early Edo period. It is made by filleting fresh fish, removing the entrails, and soaking the fish in a unique pickling liquid called kusaya eki, then letting it dry out. The name "kusaya" is said to have originated from its pungent odor, as "kusai" means "to smell bad."

On the other hand, it is likely that its strong umami flavor helped it survive to the present day. In the past, caught fish were likely filleted, soaked in brine, then dried out, much like the preparation of dried fish today, however it seems that as the pickling liquid was used again and again, it began to ferment and turn into "kusaya eki. "Kusaya eki hosts a variety of microorganisms, and these are what is thought to give the liquid its unique flavor.

Incidentally, so-called "blue-backed fish" such as amberstripe scad have long been used as an ingredient in kusaya. The reason for this is unclear, however it may be related to the species' soft flesh and bones that are easy to pickle, on top of their large population and position at the bottom of the food chain.

Japan has nurtured a diverse seafood culture, with countless dishes that could not be mentioned here due to lack of space. Intestinal bacteria are attracting attention, and microorganisms have been gaining some traction with the recent popularity of fermented foods. On the other hand, fermented fish dishes have not received nearly as much attention. In fact, many of them are quietly disappearing. However, these techniques are the encapsulation of Japanese wisdom. The reason for their disappearance may be connected to the health boom, with its somewhat skewed emphasis on reducing salt consumption. Given the future of the global environment and the food situation across the globe, it looks as though the Japanese diet will return to rice and fish. I hope we can comprehensively consider the health of ecosystems and the planet together with human health, and in doing so, have a better relationship with the culture of preserving and fermenting fish.