From the Yayoi (弥生時代) to Kofun (古墳時代) period, Katsuo was either preserved by drying the in the sun (堅魚/カタウオ/干しカツオ) or pre-boiling before drying in the sun (煮堅魚/ニカタウオ). The left over stock created by pre-boiling the bonito before drying it was also reduced down into thick sauce that was used to season food (堅魚煎汁カ/ツオノイロリ).
As Katsuo was caught in abundance along the Kuroshio Basin/Current (黒潮), it served as an important protein source for the occupants of Japan back then, and continued its role up until the Muromachi (室町時代) period. The seasoning produced by boiling down Katsuo stock was also particularly important in its role, being compared to miso and soy sauce back then.
With the advent of agricultural practices and soy production during the Muromachi period, the consumption of liquid Katsuo seasoning decreased but the consumption of sun dried Katsuo remained. Furthermore, developments in methods used to smoke the Katsuo gave rise to what was known as the first Katsuobushi, using a technique called “roasting” (焙乾). This led to the production of Katsuobushi at various areas such as Goto (五島) and Hirado (平戸), Kii Province/Kishu (紀伊國)- today’s Wakayama Prefecture, Shima City (志摩), and Tosa (土佐国).
The continual improvements in smoking techniques deployed in Kii Province/Kishu (紀伊國), combined with the growing reputation of Katsuobushi’s taste, laid the foundation of what we would come to know as Japanese cuisine, as Katsuobushi started to be used to make soup stocks in Osaka and Kyoto. The highest quality Katsuobushi back then was made in Kishu under the name Kumano Bushi (熊野節).
Back then in Tosa (土佐国), Tosa Bushi (土佐節) production had the problem of mold other than Aspergillus glaucus growing on the Katsuo fillets, causing the final products to have off flavors. The story goes on that a fisherman named Jintaro Kadoya* (角屋甚太郎) from Inami (印南浦, today:印南町), Kii Province/Kishu (紀伊國), conveyed the production methods of the famous Kumano Bushi (熊野節) mentioned above to Shimizu Cove (清水浦) in Tosa (土佐国) during the Genroku Period (元禄時代), resulting the implementation of techniques that made Kumano Bushi famous. These included a combination of smoking and sun drying to counteract unwanted mold growth, smoking using wood from the Sawtooth Oak (Quercus acutissima (クヌギ) instead of straw, and wrapping the fillets with a kind of straw wrapping known as Como Winding (コモ藁巻き), with Aspergillus glaucus innoculated on the inner surface of the wrapping to prevent the growth of unwanted mold. This allowed the production of Katsuobushi in Tosa improve in quality and durability, enough to withstand transport all the way to Osaka and Tokyo (called Edo/江戸 back then).
By then, the complete recipe used to make Katsuobushi in Tosa was supposedly Tosa’s most important secrets and was kept at Jintaro Kadoya’s hometown of Kumano in Kishu. However, legend has it that people in Satsuma managed to convince one of the original fishermen** from Inami (印南浦, today:印南町), Kii Province/Kishu (紀伊國), who had worked on helping Tosa (土佐国) make Tosa Bushi (土佐節), leak the secrets of Katsuobushi making to Satsuma (薩摩藩), thus allowing Satsuma Bushi (薩摩節) to surpass the quality of that of Kumano Bushi (熊野節). This allowed Satsuma Bushi to position itself just below Tosa Bushi in terms of quality ranking.***
In the late Edo period (江戸時代), a Katsuobushi artisan, again from Inami (印南浦, today:印南町), Kii Province/Kishu (紀伊國), named Yoichi Tosa** (土佐与市), leaked the secrets of Katsuobushi making to Awa (安房) and Izu (伊豆). This allowed Izu (伊豆) to start producing high-quality Izu Bushi (伊豆節) by applying mold to the Katsuobushi two or three times and further improving the quality by scraping off the excess fat in-between mold inoculations. Yoichi Tosa was said to have been banished from his home town in Kishu (紀伊國) for the crime of leaking the Katsuobushi recipe and died on March 23, 1815.
The final famous Katsuobushi product, Yaizu Bushi (焼津節), was derived and developed Yaizu (焼津市), Shizouka (静岡県) incorporating the production methods that made both Izu Bushi (伊豆節) and Tosa Bushi (土佐節) famous around 1980 and is thus attributed to Yoichi Tosa as well. Yaizu Bushi is also known as improved Honkarebushi (Kairyo/改良型本節).
In a sort of summary, during the Edo Period (江戸時代), the three famous Katsuobushi types were namely Shima Bushi (志摩節), Tosa Bushi (土佐節) and Satsuma Bushi (薩摩節), each corresponding with the area it was produced. During the Meiji Period (明治), the quality of Izu Bushi overtook that of Shima Bushi (志摩節) and the three celebrated types of Katsuobushi were Izu Bushi (伊豆節), Tosa Bushi (土佐節) and Satsuma Bushi (薩摩節)****. Around the year 1980, Yaizu Bushi (焼津節), came into prominence and has come to be known as today’s Honkarebushi (本枯節) that is used all over Japan today.
Today, Yaizu Bushi (焼津節), is found everywhere, whilst the only other kind of Katsuobushi still produced is Satsuma Bushi, which is made in Kagoshima (鹿児島). Whilst Yaizu Bushi is placed in a tank of water to be skinned and deboned by hand (a process known as water boning- 水骨). Satsuma Bushi is made by filleting (Namakiri/生切り/なまぎり), skinning and deboning (a process known as land boning-陸骨) the Katsuo whilst it is still raw. Anybody who has tried to do this with cooked fish or raw fish knows how much harder it is to do with raw fish. It also requires the fish to be as fresh as possible so that it is firm enough for the pin bones to be removed. This means that only very skilled craftsmen are able to make Satsuma Bushi. In fact, only two craftsmen left in Kagoshima were able to make it in 2010, both over 60 years old, Seto Inoue (井上節夫) and Moto Otsuji (尾辻求/おつじもとむ).
Yaizu Bushi can be identified by its narrow appearance, which was said to aid in hanging it up with a rope during storage. When initially cut with a filleting knife, the spine of the fish is only easier to cut through when cut closer to the head of the fish. Comparatively, Satsuma Bushi is made by cutting off the head at a 45 degree angle, making it discernible compared to Yaizu Bushi as Yaizu Bushi is more narrow. This also means that Yaizu Bushi has a higher yield.
The Tsukiji Market’s Futshitaka Katsuobushi wholesaler’s third generation owner has commented on how making Satsuma Bushi requires twice the amount of work to make compared to Yaizu Bushi but is triple the quality. However, the price of Satsuma Bushi is sold for only slightly more, meaning that less and less people are taking on the task of learning how to make Satsuma Bushi. As of 2020, Seto Inoue (井上節夫) has stopped producing Satsuma Bushi with his son quitting the trade in 2010. However, in 2010, Kubo Norihide (久保智英/くぼのりひで) took up and the mantle from Seto Inoue to continue the production of Satsuma Bushi.
*The problem is Jintaro Kadoya (角屋甚太郎) was suppose to be the founder of a technique method before that called “roasting” (焙乾) where you use smoke from the fire to dry out Katsuo fillets instead of just the sun. This technique is suppose to be from the Muromachi period (室町時代) 1336-1573 but the same Juntaro Kadoya provided the production methods of the famous Kumano Bushi (熊野節) mentioned above to Shimizu Cove (清水浦) in Tosa (土佐国) during the Genroku Period (元禄時代) 1688-1704, making him at most 368 years old.
**Unrelated to Tosa Country (土佐国) even though his name has the same characters Tosa in it. Another source also points to the idea that he leaked the secrets to Satsuma (薩摩藩) during an earlier undated period, but I couldn’t find more information on the secrets were only leaked to Izu (土佐) during the Edo period (江戸時代) 1603-1868, which means their unlikely to be the same person as he would have been many 100s of years old. Another Chinese source I found name him 土佐與一, which is also pronounced Yoichi Tosa instead of 土佐与市.
***The terms used here was 次ぐ, which with my not fantastic Japanese seemed to translate to “rank next to”, which I wasn’t sure if it meant ranked above or below. So for the sentence “土佐節に次ぐ薩摩節”, I took it to mean Tosa Bushi ranked above Satsuma Bushi and not the other way around.
**** Sanriku Bushi (Eastern Bushi/三陸節/東節) is also produced but considered to be inferior due to too high a fat content.