Kazunoko, also known as "数の子" in Japanese, is a type of food in Japan made from the eggs or ovaries (called egg skeins) of the Pacific herring, which is called kazunoko nishin in Japanese. These eggs are either salted or dried to preserve them.
Overview
Kazunoko is made by carefully taking the roe sacs (or "egg skeins") from female herrings and preserving them by sun-drying (called hoshi kazunoko) or by salting or brining (called shio kazunoko). Each egg is very small, but together they form long, oval-shaped clusters that are about 8 centimeters (3.1 inches) long and 3 centimeters (1.2 inches) wide.
Kazunoko, which represents fertility, has been a common part of the osechi assortment, a special collection of foods eaten during the New Year in Japan. Beginning around 1955, Japan’s domestic herring catches dropped sharply, and now most kazunoko comes from imports, mainly from the Pacific coasts of Canada and Alaska, as well as from Atlantic herring. A method to bleach the roe into a uniform gold color was developed, and this valuable product became known as "yellow diamond."
A type of kazunoko is called komochi kombu ("spawn on kelp"), which are Pacific herring eggs laid on seaweed, now mostly collected in British Columbia, Canada.
Historically, records of kazunoko in Japan date back to the 15th and 16th centuries. For example, it was served to Toyotomi Hideyoshi during spring. Kazunoko is harvested from herring in the spring, but by the end of the 17th century, dried kazunoko was sold as a New Year’s item. The history of making kazunoko overlaps with the history of making dried migaki nishin (a type of fish), which became common during the Kyōho period (1716–36) due to increased salt availability. Later, starting in the early 19th century, kasu (fishmeal) was also produced.
Traditionally, Indigenous people harvested spores on kelp, sometimes using hemlock branches for this purpose.
There are several economic and social challenges related to Pacific herring fishing, including modern commercial fishing taking over traditional native fishing areas. Specific issues related to herring roe include the "kazunoko ledger," a system used to track debts owed by Ainu women. Since the 1960s, North American herring fishing has focused mainly on harvesting kazunoko for the Japanese market, raising concerns about waste and sustainability.
Etymology
The words "kazunoko" and the older term "kadonoko" appear in writings from the medieval or post-medieval periods. These terms are also written using Chinese characters like 鯟子, 鰊子, 鯡子, 鯑, and 䱧.
There are two or three theories about how the word "kazunoko" originated.
One theory suggests that "kazunoko" comes from "kado no ko," where "kado" was an old name for herring. This explanation is found in a book called Honchō shokkan, published in 1697. The book explains that the character 鯟 (kado) is pronounced as "kato" or "kado." It also notes that "kazunoko" (數子) was once written as "ka-to-no-ko" (加登乃古/加豆乃古). Even after the Edo Period, the word "kado" or "kado iwashi" was still used in some dialects to refer to herring, even though "nishin" is the standard Japanese term for the fish.
Another theory suggests that "kazunoko" might mean "child of numbers" or "child of numerousness." This idea was proposed by Ōishi Chibiki in his work Gengentei (1830/1834). Early writings of the word also used the form "kazunoko."
A third theory is mentioned in an Edo Period essay called Kiyū shōran (1830). It states that "kazunoko" was sometimes called "kazukazu" (かずかず) in the language used by women during that time. This is connected to a term "kozukozu" (cod organ), which was mentioned in Muromachi period writings as a New Year’s dish. The Daigenkai dictionary links these two similar-sounding terms as possibly related.
Some people think the Japanese word "kado" might come from an Ainu word, but the known Ainu word for "herring" is "heroki" (with other spellings). However, linguist Minoru Umegaki does not support this idea.
Japanese cuisine
Kazunoko in Japan is divided into three main types: hoshi kazunoko (dried herring roe), shio kazunoko (salted herring roe), and ajitsuke kazunoko (flavored herring roe).
Currently, only small amounts of dried kazunoko are produced. The flavored version made from Atlantic herring roe is sometimes called a "secondary market" or "substitute" product by American sources, though this topic is discussed further.
Kazunoko is a traditional part of a New Year’s dish called osechi. It is often marinated in soy sauce to last for days or used in a dish called kasuzuke.
Kitaōji Rosanjin, a respected food expert and restaurant owner, once said that while raw or salted kazunoko was becoming available, dried kazunoko rehydrated with water was considered the best in taste (as noted in his 1930 essay, "Kazunoko is about eating the sound"). Typically, kazunoko is served with bonito flakes and soy sauce, but Rosanjin believed the sauce should not soak in too much. He also avoided adding other flavors like miso or sakekasu or marinating it in soy sauce. Others, however, argue that dried kazunoko becomes more flavorful when soy sauce is allowed to soak in.
Matsumaezuke is a soy-pickled dish that includes pieces of kazunoko, along with dried squid (surume) and kombu seaweed. Kazunoko was added to this dish in 1929, changing a recipe that originally only used squid and kelp.
Kazunoko is known for its crunchy texture, which is described with the onomatopoeic sound "puchi puchi." The Atlantic herring is generally less crunchy, so it is often used for flavored kazunoko or as a side dish. However, some Atlantic herring from the Baltic and North Sea regions are used to make salted or brined kazunoko. The Baltic subspecies (C. harengus menbrus) is considered the best among Atlantic herring for making salted kazunoko.
Another dish, "komochi kombu" (also called kazunoko kombu), is made by placing herring roe on kelp. It can be eaten alone or used in sushi and is sometimes very expensive.
In Hokkaido, only a small amount of Japanese herring is caught, and even less is used for harvesting eggs. Studies show that herring roe from British Columbia, Alaska (Sitka or Kah Shakes Cove), and the Baltic Sea produces high-quality eggs suitable for salting or drying.
Atlantic herring roe is generally softer than other types but is not always used for flavored kazunoko. Some Atlantic herring, especially from the Baltic Sea, North Sea, Scotland (Shetlands), Ireland, and the Netherlands, are used for salted kazunoko. Quality is also judged by how well the eggs stick together; eggs that fall apart easily are not used for whole salted kazunoko.
The Atlantic herring has less crunchiness (called hagotae) than other types. One study found that Atlantic herring does not solidify as firmly and is mostly used for flavored kazunoko. However, the Baltic Sea herring is considered the best among Atlantic herring for making salted kazunoko, even though its eggs are smaller.
A study of Edo Period foods, including kazunoko, analyzed its nutritional value. While kazunoko is high in cholesterol (like most fish roe), it also contains high levels of EPA and DHA fatty acids, which help lower cholesterol. Herring is classified as an aozakana (blue fish), a group known for omega-3 fatty acids. However, herring was once avoided by people with gout due to its purine content. Recent studies suggest this warning no longer applies unless the herring is dried or semi-dried. Kazunoko has very low purine levels (<50 mg per 100g), making it safer for people with gout or hyperuricemia (a condition linked to gout). Similar dietary advice applies to those with hyperuricemia.
History
In Japan, the tradition of serving kazunoko (herring roe) during the New Year may have started during the Muromachi Period, according to some sources. A record from the mid-Muromachi Period Diary of Ninagawa Chikamoto (1465) mentions a dish called kozukozu, which was actually the milt (reproductive fluid) of male cod. Some dictionaries later referred to kozukozu as an alternate name for kazunoko. Earlier records, such as the Satsujōshū (1454), describe kazunoko as the eggs of the kado fish, and it was listed alongside another name for kozukozu, called kurukuru.
The name kazunoko appears in menus from the later Muromachi Period and the Azuchi–Momoyama Period. It was served during a visit by the Ashikaga shogunate to Echizen Province in 1568, as recorded in the Asakura-tei onariki. Later, in 1594, Toyotomi Hideyoshi was served kazunoko during a visit by the Maeda clan of Kaga Province, as noted in the Kaga no chūnagon dono e onari no koto.
During the Edo Period, documents from the Kanbun era (1661–1673) mention shipments of dried herring and kazunoko from Ezo (modern-day Hokkaido). A book called Honchō shokkan (1697) states that kazunoko was sold in markets during the 12th and 1st lunar months.
Until salt became more widely available, the variety of herring products was limited. By the Kyōho Period, new items like migaki nishin (processed herring) and kazunoko were produced, along with dried milt, gills, and guts used for fertilizer. An 18th-century artwork titled Esashi-hama nishin no zu shows these products being made. Damaged kazunoko was used as fertilizer. Kasu (herring meal) was not made at this time and began production later in the 19th century.
Matsumae clan records from 1717 show kazunoko being shipped from various provinces, with dried milt and herring sent to the Chūgoku and Ōmi regions. Some sources say kazunoko was used as fertilizer, while others describe it as a food item. Records also mention yose kazunoko (processed kazunoko shaped into squares or discs) being sent as tribute to the shogunate. During the Tokugawa Period, kazunoko was packed in straw containers and later reboxed in Osaka.
A 1719 memorandum from a beach official listed kazunoko and yose kazunoko as tribute items to the shogunate. Yose kazunoko was made by separating the eggs, removing stringy tissue, and shaping them into squares or discs.
In the 19th century, kazunoko became a byproduct of herring meal (nishin kasu), which replaced expensive fertilizer from dried sardines. The 8th Tokugawa shogun, Yoshimune, promoted frugality and created a New Year’s menu with three snacks: kazunoko, gomame (anchovy dish), and black soybeans.
By the 19th century, salted kazunoko (shio kazunoko) was available and served as a tribute to the shogunate. A Kyoto restaurant reportedly charged a high price for a dish of it during the Bunka or Tenpō eras.
Processing methods
Domestically caught kazunoko in Japan were mainly the dried type. Although some roe was eaten fresh locally, most was harvested as a byproduct of dried herring (migaki nishin). The "salted" (or brined) type became more common only after 1954–1955, when the domestic herring fishery declined.
There are different grades of dried kazunoko. According to government records from the Taishō era, production of hokawari nishin (a type of migaki nishin with the spine removed) involved removing the hararago (roe skein), which were then cleaned in water, sun-dried on straw mats, and graded by size and quality.
Older methods dried the roe without rinsing, causing blood tissues to darken the roe. This process was called kokkan hō ("black-drying method") and was abandoned by the Showa era. Later methods included "modified" and "semi-modified" techniques. Both involved soaking the roe in saltwater until blood was removed. The modified method used precise 4% saltwater and required careful handling of each roe piece, while the semi-modified method used seawater and placed the roe on bamboo drip trays.
Salted or shio kazunoko was mentioned earlier as tribute to the shogunate. Some seafood processors claim production began in the 1900s (Meiji 30s). By 1894, shio kazunoko was made by washing the roe in water and then salting it in a tub. Later, the roe was cured in saline or saturated saline solutions.
The "salted" kazunoko became more popular in the 1960s. After 1954, herring catches near Hokkaido dropped, and dried kazunoko declined, allowing salted types to take over the market.
Modern methods often call the product "brined" rather than "salted." Sodium chloride solution is used in three steps: first, brining the herring to stiffen the roe for removal; second, washing the roe in weak saltwater; and third, curing it in saturated brine.
After domestic herring supplies ran out, frozen herring from former Soviet (Russian) sources was imported. Around 1960, shio kazunoko gained a reputation for strong odors and lower quality compared to dried versions. In 1963, a company in Rumoi, Hokkaido, developed a method to bleach kazunoko using hydrogen peroxide. This reduced odor and turned the roe golden yellow, earning it the nickname "yellow diamond" and making it a high-value product.
Bleaching is still used in kazunoko production. Although enzymes were used to remove residues, concerns arose when studies found that hydrogen peroxide posed a minor cancer risk to rats lacking the enzyme catalase. In 1980, the Ministry of Health and Welfare required zero residual peroxide in food, leading other industries to stop using it, but kazunoko producers continued.
Extracting roe from fresh herring was once a delicate process. In pre-industrial times, fishermen in Esashi, Ezo, carefully removed herring from gillnets without damaging the eggs. Extracting roe and milt, called nishin tsubushi ("herring crushing"), was considered women’s work. Fish were gutted by hand using finger cots, and the roe was dried into hoshi kazunoko. Some broken pieces were used as fertilizer, along with dried milt and gills.
Herring-squeezing (roe stripping) often relied on Ainu women. In Sōya, northern Hokkaido, adult Ainu women (menoko) performed this work, as recorded in a 1792 text about Ezo customs. Merchants traded goods to the Ainu in exchange for labor, and debts were recorded on kazunokocho (debt ledgers). At Aniva Bay, Ainu repaid loans by making grass screens (sudare) and delivering them after winter. Outstanding debts were tracked on kazunokocho, requiring service in kazunoko production.
According to the 1792 text, milt could be dried immediately, but kazunoko needed to rest in boxes or barrels for 2–3 days before sun-drying to avoid breaking.
During the Showa era, before freezing technology was common, roe was stripped manually from fresh herring.
In Alaska, early 1960s roe stripping used a rough method: herring were piled with salt, left to age for 4–5 days, and then roe was easily removed. This method lasted until the mid-1970s, when frozen herring were shipped to Japan. Freezing made roe easier to remove and avoided waste from high-salt solutions, though improper freezing could cause a spongy texture.
Some kazunoko were molded into disks or squares (yose kazunoko) and given to the shogun. Later, stray eggs were collected, solidified, and cut into flower shapes (hana kazunoko) for sale. Imitation kazunoko was also made using capelin eggs, sometimes mixed
Fishing grounds
The main fishing areas for herring were in Hokkaido (formerly called Ezochi), where herring schools that feed and lay eggs on the Sea of Japan side were targeted. Because of this, the Matsumae clan managed the main production center in Esashi (or Matsumae) on the southwestern coast. Later, the clan expanded its control over fishing areas north and east, reaching as far as Southern Sakhalin (Minami Karafuto), and opened Hakodate port on the east coast.
The Matsumae clan hired merchants at trading posts called basho or akinaiba to handle fishing and trade under a system called basho ukeoi – sei. At times, the clan lost control of the fishing areas and trade in Ezo to the central government (shogunate) due to concerns about a Russian threat. As a result, herring production in Sakhalin changed hands between Japanese control (during the Tokugawa period, Meiji era, and Showa era) and Russia (after World War II), including kazunoko.
Around 1955 (Showa 30), the main fishing areas on the Sea of Japan side declined, forcing Japanese herring ships to operate on a smaller scale, targeting smaller herring groups or fishing in the Gulf of Patience and Aniva Bay in Southern Sakhalin. In the 1960s and 1970s, egg-bearing herring were imported from Russia. Starting around 1960, larger amounts of herring were also imported from Alaska. In 1980 (Showa 55), the herring roe industry faced a major decline. Prices rose sharply, and rumors of hoarding led to government restrictions on peroxide bleaching agents. The market stopped buying, leaving companies with large amounts of overpriced herring roe.
As previously discussed, Japan now mainly imports Pacific herring roe from British Columbia, Canada, Alaska, and the United States, as well as Atlantic herring roe from Europe.
Alaska has some of the shortest fishing seasons, sometimes lasting only a few hours. In 2022, fishing quotas for roe herring were set as follows: 45,164 short tons (90 million pounds) in Sitka Sound in late March, 8,075 short tons (16 million pounds) in Kodiak Island in April, and 65,107 short tons (130 million pounds) in Togiak in May. However, full quotas were not reached. Japanese demand for herring roe decreased, and prices dropped from $1,000 per ton in the 1990s to much lower levels by 2020. In 2023, Togiak’s last processing plant announced it would not buy herring for the following year, and the fishing season was canceled.
There has been criticism about harvesting herring in Alaska mainly for roe, as most of the fish—about 90% of the total weight—were discarded until the 1990s and turned into sludge. This practice was later replaced by using the leftover material as pet food or fertilizer. However, concerns remain about the inefficient use of resources from a scientific perspective. Similar issues with sludge waste have also been discussed in connection with Canadian processing plants, referred to as "stickwater" in some literature.
First Nations food source
The native peoples of the Pacific coast of Canada and Alaska, which are now major areas for producing kazunoko, have a tradition of gathering herring eggs on seafood or wood branches during the spring herring runs when the fish come to spawn.
The Sitka, Alaska area was one of the oldest Tlingit village settlements. People there have collected herring eggs on seaweed or hemlock branches for a very long time, as reported by descendants. These eggs are called "spawn on kelp" (Tlingit: daaw) or "spawn on hemlock" (Tlingit: haaw). One type of seaweed used is called "hair kelp" or "hair seaweed," though it is not a true kelp. This seaweed is identified as Desmarestia sp. or more specifically Desmarestia viridis, which belongs to a group of seaweeds that are not classified as kelp. There are many accounts from European explorers in the 18th and 19th centuries about these practices.
The Haida, who live in Haida Gwaii (formerly Queen Charlotte Islands) in Canada, also traditionally gather k'aaw. These eggs can be eaten fresh, or they can be sun-dried. Dried eggs may be eaten as is or rehydrated in water and then boiled or fried.
A type of seaweed known in Haida as "raven's moustache" (x̱uya sg̱yuug̱a) is mentioned in Haida stories. This seaweed is said to be less effective than hemlock branches for gathering eggs. It is likely a type of Desmarestia seaweed. Western Hemlock (Tsuga heterophylla) is the tree used to collect the eggs. A Haida origin story explains that when Raven touched his beak to the dancing hall of the Herring People, the eggs stuck to his mustache and were not tasty. He discarded the mustache, which became seaweed. He then used a hemlock branch, which grew with tasty eggs. This story teaches that hemlock is the better tool for gathering eggs.
On the opposite side of the region live the Tsimshian of Lax Kwʼalaams (formerly Port Simpson), who also practiced egg-gathering. In Tsimshian languages, spawn on hemlock branches are called xs'waanx, and spawn on kelp are called gyoos, meaning "kelp."
In the Bristol Bay area, which is in the far east of the Bering Sea, including Togiak and nearby communities, the Yup'ik Eskimo also traditionally fished for herring and collected their eggs. The spawn on kelp (Central Alaskan Yupʼik: qaryaq) is preserved by freezing, salting, or drying and is usually eaten with seal oil. Yup'ik people on Nelson Island (Alaska) also go to sea to collect spawn on kelp. While they often eat the eggs quickly, they may preserve them in seal oil inside a sealskin container (puuq), similar to how they preserve herring. In the Bering Strait region, which is mainly Iñupiat Eskimo territory, an informant from Stebbins (a community settled by Nelson Islanders) stated that collecting spawn on kelp (Yup'ik, Neson-Stebbins subdialect: ellquat) is a long-standing tradition. The Iñupiat in the area also gather and eat herring eggs.
Ainu cuisine
In Ainu cuisine, there is a dish named after the cow parsnip, Heracleum lanatum (also known as Heracleum maximum). The plant is called pittok (ピットㇰ) or siturukina (シト゜ルキナ) in the Ainu language. The stems, or more specifically the stalks of the radical leaves, are peeled, preserved, and later soaked and cut into pieces. Dried herring roe (Ainu: pere (ペレ/ぺレー)) and seal fat are pounded together until they become a milky white mixture. This mixture is combined with the vegetable and diatomaceous earth, which is added to reduce bitterness. The liquid squeezed from this dish was used as a substitute for milk for infants.
In poetry
In haiku poetry, kazunoko is a kigo (季語; "season word") that represents the New Year season and jinji (human affairs). An example is the poem "Kazunoko ni itokenaki ha wo narashi keri" (数の子にいとけなき歯を鳴らしけり; "Herring roe, upon which the young 'uns teeth resound"), written by Mokkoku Tamura [ja].