What is hybrid artificial fish?

A photo of Kue-tama
The appearance of Kue-tama

What is hybrid fish?

Both Yamame (Landlocked Sakuramasu) and Japanese Iwana (Char) are members of the salmon family. Iwana and Yamame both inhabit the upper reaches of rivers, although Iwana prefers slightly cooler water. In rivers where each species lives alone, both fish occupy the upper reaches of the river, but in rivers where both species live, they do not mix, with Iwana occupying the uppermost reaches and Yamame occupying the lower reaches after a certain point in the upper reaches.

In nature, different species sometimes interbreed and produce hybrid fish. For example, hybrids between Yamame and Iwana are common in nature. The characteristic spots of the Iwana look like those of the Saba (Mackerel), a marine fish, and hence the name Kawasaba. They also rarely become smoltified (silvering) and become the descending sea type, but they do not reach sexual maturity.

Incidentally, the Kawasaba is thought to have been created by the uncontrolled release of Yamame into an area originally inhabited by Iwana, resulting in the mating of two species whose habitats do not originally overlap. The “hybrids” created by thoughtless releases may be a symbol of the destruction of genetic diversity.


What is hybrid artificial fish?

In the aquaculture industry, high growth and survival rates, good flesh quality, and disease resistance are important requirements for a superior species, and artificial crossbreeding has long been used as a method to create such breeds.

In 1964, Kinki University in Japan succeeded in breeding the first hybrid artificial fish, a female Red seabream (Madai) with a male Blackhead seabream (Kurodai). Since then, he has produced many hybrid combinations. The name “Ma-kurodai” is a combination of “Madai” and “Kurodai. In addition, he has created nearly 20 new fish species, including Madai x Hedai (Ma-hedai), Madai x Chidai (Ma-chidai), Ishidai x Ishigakidai (Kin-dai), and Buri x Hiramasa (Buri-hira).


Typical hybrid artificial fish will be mentioned briefly.

What is Buri-hira?

Buri hira is a crossbreed between a female Japanese amberjack (Buri) and a male Goldstriped amberjack (Hiramasa). Buri, which is in season in winter, is characterized by its high fat content and strong flavor, but its meat is tender and its dark red meat (chiai) tends to discolor during the summer. Hiramasa, on the other hand, is firm, has less dark red meat (chiai), and is less prone to discoloration, but has less fat and a lighter flavor, and is only available in summer.

Buri-hira is a very tasty fish that combines the “good points” of these two fish species and combines the “umami” of Buri with the ” chewiness and beauty” of Hiramasa. Because it is completely farm-raised, it can be served all year round, and major conveyor-belt sushi chains have already begun serving Buri-hira. Buri-hira can be caught in the wild very rarely, but they are so few that they are not generally available on the market.


What is Kue-tama?

It is a hybrid species, having as its father a Giant grouper (Tamakai), one of the world’s largest members of the grouper family that can grow to 270 cm in length and 400 kg in weight, and as its mother a Longtooth grouper (Kue), which is a rare and high-end fish with an outstanding taste and popularity.

The hybrid is characterized by the fact that it inherits the growth rate of Tamakai and grows to shipping size in about two years, whereas it normally takes four to five years for farmed Kue to grow to shipping size.

This makes it possible to significantly reduce production costs, and it also has properties that make it resistant to disease and easy to grow. Major conveyor-belt sushi chains have already begun offering Kue-tama.


What is Be-ster?

Be-ster is a hybrid of Beluga and Sterlet, known for producing the finest caviar among sturgeon. Developed by Russia several decades ago for aquaculture, the Be-ster was created amid a worldwide ban on capturing wild sturgeon as an endangered species.


What is Kin-dai?

Kin-dai is a hybrid of a female Barred knifejaw (Ishidai) and a male Spotted knifejaw (Ishigakidai) and was first successfully produced by Kinki University in 1969, and patented and trademarked in 1975.

Ishigakidai, on the other hand, takes more than six years to mature and produces fewer eggs, but grows quickly to commercial size. Kin-dai combines the best features of both, with a good texture and excellent taste. Its name is the same as the abbreviation for Kinki University.

Ishidai is called “Kuchiguro (kuchi means mouth and guro means black)” because its body turns silvery white and the area around its mouth turns black. Ishigakidai, on the other hand, is called “Kuchisiro (shiro means white)” because they have a black body and the area around their mouth turns white. Kin-dai’s entire body turns black, and the tip of its mouth also turns black.


What is Ma-chidai?

Kinki University has also produced a hybrid Ma-chidai, a cross between Red seabream (Madai), which grows well, and Crimson seabream Chidai, which has a less faded red coloration, and has traits that give it a red coloration like natural fish and faster growth than Chidai.

Finally, a second generation has already been produced from the sexes of the hybrid fish. If the hybrid fish are released into natural waters, contamination will occur through genetic infiltration. We should not leave a bad legacy for future generations.

What is Torokinme?

A photo of Fusenkinme.

Fusenkinme (Red bream) is occasionally caught along with Splendid alfonsino (Kinmedai). Until recently, they were considered to be the same species. Kinmedai has elongated slit-like posterior nostrils, while Fusenkinme has oval-shaped posterior nostrils. Kinmedai can grow over 50 cm long, whereas Fusenkinme stops at 40 cm.

Fusenkinme is fattier than Kinmedai and is called Aburakinme or Torokinme by fishermen, in areas that distinguish between Fusenkinme and Kinmedai, there is a difference in market price, but it is rarely distributed and is consumed locally.

Torokinme does not refer to the belly part of Kinmedai but to Fusenkinme, a rare species of Kinmedai. Incidentally, three Kinmedai, Nanyokinme, and Fusenkinme species are distributed in Japan.

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What is the thought behind Toro?

What is Torokarei?

A photo of Torokarei fillet
The appearance of Torokarei fillet

Consumers are inevitably confused by the word Toro. It isn’t easy to separate the word from a mere marketing term. Therefore, the market contains fish names with Toro as a prefix.

Torokarei (karei means flounder) is a trade name for a fish named after the toro of tuna, which has a rich, tender texture, and is an arrowtooth halibut (Aburakarei).

Aburakarei is distributed north of Choshi, the northern Sea of Japan, the Sea of Okhotsk, and the western Bering Sea. Aburakarei is a typical eating fish among flounder species, and unfortunately, it is considered the most tasteless and has low commercial value. Black halibut (Karasugare), a relatively tasty and inexpensive fish, has become expensive, so perhaps it is Aburakarei’s turn.

So a name that would sell was needed, so it became Torokarei.

In recent years, Aburakarei has been imported from the U.S. and other countries in large quantities of fillets processed for frying. It is inexpensive and its distribution is stable. Aburakarei is characterized by its meat containing so much fat that it melts when heated. Even when heated, the flesh remains tender, and it is often used overseas for frying as fish and chips. The most common type of engawa at conveyor-belt sushi restaurants is either Aburagarei or Karasugarei.

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What is the thought behind Toro?

What is Kudoa septempunctata?

A photo of Kudoa septempunctataKudoa septempunctata is a species of parasite (mucous sporozoite) of the genus Kudoa that parasitizes Bastard Hailbit (Hirame). It is approximately 10 µm in size and has a “hemispherical” shape when parasitized on fish.

Most cases of food poisoning due to cudweed are associated with fresh flatfish for raw consumption (e.g., flatfish sashimi). The infection rate and amount of infection are particularly high in farmed flatfish, which accounts for 60% of the food ingredients that cause kudoa food poisoning.

It is characterized by transient vomiting and diarrhea within a few hours after eating, with symptoms ending in a mild illness. Kudua has been shown to lose its virulence by freezing at -20°C for 4 hours or more, or by heating to a core temperature of 75°C for 5 minutes or more.

Therefore, food poisoning can be prevented by freezing it once and then eating or cooking it.

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Studies on Seasonal Changes in Occurrence of Food-Borne Disease Associated with Kudoa septempunctata

We hope this information will be helpful.

Revision date: April 13, 2024

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