Raw eel blood is toxic, which is why unagi sushi never comes uncooked. What sits on the rice is a charcoal-grilled fillet of freshwater eel, glazed with sweet soy tare.
The word unagi covers more than one fish, though. A 2025 Fisheries Science study looked at 134 grilled eel products bought at Japanese retailers in 2024. Every domestic product was Japanese eel. Imports, mostly from China, were dominated by American eel.
What Is Unagi Sushi?
Order unagi at a sushi counter and you get grilled freshwater eel in a sweet soy glaze, set on seasoned rice. “Unagi” is the Japanese word for freshwater eel, so it names the fish and the dish both. Some menus just call it eel sushi.
The classic form is hand-pressed nigiri. A glazed slice of eel goes on a mound of rice, and a thin nori band holds it in place.
The eel is split and grilled. The sweet soy glaze, called tare, gets brushed on while it cooks. Underneath is short-grain sushi rice, seasoned the usual way.
The traditional eel is the Japanese eel, Anguilla japonica. European eel (Anguilla anguilla) and American eel (Anguilla rostrata) are eaten too.
It isn’t raw fish, either. Anago, the saltwater conger eel, is a different animal with a lighter flavor.
What Does Unagi Sushi Taste Like?
Sweetness comes first, from the glaze. The flesh is soft and fatty, and the grill leaves a smoky edge.
The fat explains most of it. Cooked eel (mixed species, dry heat) holds 14.9 g of fat per 100 g beside 23.6 g of protein, per USDA FoodData Central.
Most of the sweetness is tare. The char is just the grill.
Food Republic describes the result as a sweeter take on a firm white fish such as bass.
The flesh is tender but firm enough to stay on the rice. There are small bones, and they’re soft enough to eat. Unlike saltwater eel, there’s no fishy aftertaste.
How Is Unagi Prepared for Sushi?
The method is called kabayaki. The eel gets split, boned, skewered, grilled and basted with tare until it’s glazed.
The steps below follow the Kanto (Tokyo) method, which adds a steaming stage that Kansai cooks skip.
- Split the eel open (down the back in Kanto), then remove the bones and head.
- Cut the butterflied eel into fillets and skewer them.
- Grill the fillets plain, with no sauce.
- Steam the grilled fillets to render out fat and soften the flesh.
- Grill again over charcoal while basting the fillets repeatedly with tare.
- Slice the glazed fillet into portions and set it on rice.
Eel sold at supermarket sushi counters is often pre-cooked and only reheated, sometimes with a torch. Shirayaki is the unglazed variant, grilled plain and seasoned with salt.
Kanto and Kansai Styles
In Kanto the eel is split from the back and steamed before the final grill. Kansai cooks go in from the belly and grill straight through, no steaming.
| Attribute | Kanto (Tokyo) | Kansai (Osaka, Kyoto) |
|---|---|---|
| Split from | Back | Belly |
| Steaming | Yes, between two grillings | No, grilled throughout |
| Texture | Soft, fluffy, less fat | Crisper skin, chewier, more fat |
| Head | Removed | Often left on |
The split direction goes back to Edo, where cutting the belly recalled seppuku for the samurai clientele, according to Hamamatsu’s visitor guide.
Steaming is the younger habit. Nippon.com reports that Tokyo cooks did not steam unagi before grilling until well into the Meiji era (1868 to 1912), though other sources place the steaming step in the late Edo period.
In Tokyo, Maruichi Fuji Akasaka still grills Kansai style and skips the steam (byFood).
What Is in Unagi Sauce?
Tare, also called nitsume, is soy sauce, mirin, sugar and sake cooked down into a glaze.
Soy sauce is the salty, umami base. Mirin, a sweet rice wine, adds gloss, and the sugar sweetens the glaze while helping it thicken as it reduces. Sake is optional, since some recipes leave out the rice wine altogether.
Food Network cites a 1:1:0.5:0.5 ratio of soy sauce to mirin to sake to sugar, and individual kitchens adjust it.
Despite the name, eel sauce contains no eel.
Is Unagi Sushi Ever Served Raw?
Never. Raw eel blood carries a toxic protein that heat destroys, which is why unagi doesn’t show up as sashimi or as a raw topping.
The toxin sits in the blood serum, and sources call it ichthyotoxin or ichthyohemotoxin. A 2008 Springer-published study purified it from Japanese eel as a single protein of about 100 kDa, with an LD50 of 670 micrograms per kilogram in mice by intravenous injection.
Toho University researchers (a grant project completed in fiscal 2022) identified the gene and found a serum protein of about 115 kDa. Heat-denatured toxin lost its activity in vitro and in vivo, so the protein’s three-dimensional structure carries the toxicity.
How dangerous raw eel is in practice depends on who you ask. Food media such as Tasting Table warn that even a small amount of raw blood can kill. VAPAGuide, a clinical reference on poisonous animals, calls poisoning extremely rare, with no recent reports, and says gastric juices also inactivate the toxin.
The mouse figure above comes from injection, which is not the same route as eating. Neither position changes the menu rule.
Cooking covers the blood toxin and nothing else. Ciguatoxin is a separate problem that cooking does not neutralize, and VAPAGuide lists moray, conger and snake eels as potentially ciguatoxic, a risk it does not attach to freshwater Anguillidae.
Unagi vs Anago: What Is the Difference?
Anago is the milder one. It’s saltwater conger eel, lighter and softer than unagi, and it’s usually simmered or grilled. Unagi is freshwater eel, grilled and glazed with tare.
| Attribute | Unagi | Anago |
|---|---|---|
| Fish | Japanese eel (Anguilla japonica) | Whitespotted conger (Conger myriaster) |
| Habitat | Spawns at sea, matures in rivers | Lives its whole life in the sea |
| Flavor | Fatty, rich, sweet-savory | Delicate, light, softer |
| Usual cooking | Grilled with tare | Simmered, or grilled |
| Look | Dark gray to near-black skin, rounded tail | Brownish skin, white spots, pointed tail |
| Supply pressure | IUCN Endangered, farmed from wild glass eels | Wild-caught, with local stock declines |
Cooking splits along regional lines too. A Hiroshima University fishery study notes that grilled anago is preferred in Kansai, while simmered anago is popular in Kanto.
Sources disagree on how far the two can stand in for each other. Just One Cookbook calls anago an easy swap in rice bowls and rolls, while Sushi Zo chef Masashi Ito puts unagi ahead on fat and richness (Food Republic, 2016).
Order unagi for the fat and the char, and anago when a lighter piece is the goal.
How Is Unagi Served Beyond Nigiri?
Past the nigiri at the counter, unagi shows up in rolls, in the rice bowls called unadon and unaju, and as hitsumabushi in Nagoya.
| Form | How the eel is served | Usual setting |
|---|---|---|
| Nigiri | Glazed slice on a rice mound | Sushi counters |
| Roll | Inside, or layered on top, with avocado or cucumber | Western-style sushi menus |
| Unadon | Kabayaki over rice in a donburi bowl | Eel restaurants |
| Unaju | The same eel in a tiered lacquer box, the fancier form | Eel restaurants |
| Hitsumabushi | Chopped eel over rice in a wooden container | Nagoya |
Sushi Forms
Nigiri stays the counter standard. Eel also gets used in several inside-out sushi roll styles, almost always paired with avocado or cucumber.
The dragon roll layers eel and avocado over the roll, and it’s a fusion style rather than a traditional Japanese one. The caterpillar roll puts eel and cucumber inside, with avocado slices on top.
Menus use the names loosely. Sushi Sushi’s recipe page treats the dragon roll and caterpillar roll as one roll, while other recipe sites keep them apart.
Rice Dishes
Unadon is the simple one, sliced kabayaki over rice in a donburi bowl. Put the same eel in a tiered lacquer box (jubako) and it becomes unaju.
Hitsumabushi works differently. The chopped eel on rice gets split into four portions: plain, with condiments, as ochazuke in tea or broth, then whichever way you liked best.
Condiments for hitsumabushi vary by restaurant and include green onion, wasabi and sansho, a Japanese pepper. Nagoya’s food promotion site dates the dish to the late Meiji period, when it became the last course at banquets.
The Midsummer Day of the Ox
Japan eats unagi for stamina on doyo no ushi no hi, the midsummer Day of the Ox.
The pairing began in Edo. Japan Journal (2025) credits Hiraga Gennai, who advised an eel seller on slow summer sales, and calls the link his invention, though it notes a nutritional basis exists. Other sources treat the Gennai story as an unverified legend.
Eating eel against summer fatigue is older than that. Traditional Kyoto points to an early mention in the Manyoshu, an 8th-century poetry anthology, while the Day of the Ox custom itself dates to Edo.
Is Unagi Sushi Sustainable?
Not by default. The IUCN lists the Japanese eel as Endangered, and most farmed eel still starts as wild-caught glass eels.
The IUCN puts the decline in eel populations at up to 90 percent over 30 years (reported by AP, 2014).
At CoP20, the vote rejecting an Appendix II listing of Japanese eel, American eel and all other Anguilla species went 100 against, 35 for, with 8 abstaining (Government of Canada, 2025).
The East Asia-wide cap on glass eel input for Japanese eel farming is 78.8 tonnes (WWF Japan, 2025).
One hatchery-bred juvenile eel cost 1,800 yen in 2026. That’s down from 40,000 yen in 2016 and still three to four times the price of a wild juvenile (AFP, May 2026).
Conservation Status by Species
The IUCN, CITES and FAO do not rate the same eels the same way.
| Species | IUCN Red List | CITES (October 2026) |
|---|---|---|
| Japanese eel (Anguilla japonica) | Endangered | Not listed |
| European eel (Anguilla anguilla) | Critically Endangered | Appendix II |
| American eel (Anguilla rostrata) | Endangered | Not listed |
| Shortfin eel (Anguilla bicolor) | Near Threatened (2014 report) | Not listed |
The IUCN designated the Japanese eel Endangered in 2014, and the reassessment published in 2020 kept that category (PLOS ONE, 2025). Japan’s Ministry of the Environment had added it to the country’s own red list a year earlier (AP, 2014).
The disagreement sits in the CITES column. The FAO Expert Advisory Panel concluded in 2025 that the Japanese and American eel proposal did not meet the listing criteria on grounds of population decline (Undercurrent News, September 2025), and Japan’s delegate repeated that view before the vote.
CITES had chosen monitoring over trade restrictions for Japanese eel once before, at the Johannesburg meeting, according to SeafoodSource. The 2025 proposal covered Japanese eel and American eel in their own right, and the other Anguilla species as look-alikes of the already listed European eel or of those two species.
Why Farmed Eel Is Not a Closed Cycle
Japan limits how many wild glass eels go into farm ponds, and a traceability law for domestically caught glass eels took effect in December 2025 (WWF Japan, 2025; Japan’s Ministry of Agriculture, Forestry and Fisheries, 2026).
Most farmed eel still starts as wild seed, glass eels of about 0.2 g each (FAO) caught at river mouths. Hatchery seed was first achieved in 2010 by Japan’s national fisheries researchers, and output is now at tens of thousands of juveniles a year (Yomiuri Shimbun via Asia News Network, May 2026).
By that arithmetic, 78.8 tonnes of glass eels at about 0.2 g each is roughly 390 million fish. Hatchery output is a tiny fraction of that scale.
Yamada Suisan began trial sales of fully farmed eels on May 29, 2026, the first such sales reported anywhere.
What to Order Instead
Order anago, or skip eel, when the species and origin are unknown.
Anago is not a free pass. A 2022 Marine Biology study of whitespotted conger describes a drastic decline in its fisheries stock and links growth to prey availability and sea temperature, and an Aichi Fisheries Research Institute analysis found conger catches in Ise Bay falling since around 2010.
Shortfin eel has served as a substitute for Japanese eel, and SeafoodSource (2014) reported the IUCN’s warning that shifting demand could quickly worsen its Near Threatened status.
Seafood Watch’s November 2021 update kept pond-farmed American eel from China, Japan, South Korea and Taiwan at Avoid.
Several Anguilla species are frequently mixed within shipments, according to the CITES proposal text (CoP20 Prop. 35). A menu line that says only “eel” does not name the species.
Unagi Sushi FAQ
How healthy is unagi sushi, and how many calories does it have?
Plain cooked eel carries 236 kcal and 161 mg of cholesterol per 100 g (USDA FoodData Central), so it is rich rather than light.
The rice and the sugary tare in a finished piece add calories and sodium on top.
Why is unagi so expensive?
Long-run supply has shrunk. Japan’s eel supply fell to 60,941 tons in 2024, about 40 percent of the 2000 peak (Asia News Network, 2026).
Tokyo’s wholesale market averaged 5,553 yen per kilogram in May 2023 (Nippon.com Japan Data). Prices have eased since: wholesale prices for domestic eel fell from 5,307 yen in April 2025 to 2,983 yen in April 2026 after strong glass eel catches (News On Japan, 2026).
How long does cooked unagi keep, and can it be frozen?
Eat opened cooked unagi within a few days and skip freezing leftovers, according to Just One Cookbook.
Unopened retail packs are a different case, since counters often sell frozen roasted eel that is thawed before use (Sift & Simmer).
Can you buy pre-cooked unagi for homemade sushi?
Yes. Asian grocery stores and supermarket sushi counters sell pre-cooked unagi, whole or sliced, and some packs already carry tare, so go easy on extra sauce.
Cheaper packs are most likely imported from China, South Korea or Taiwan (Just One Cookbook), so check the origin line on the label.
Finding Out Which Eel Is on Your Plate
Unagi sushi carries no species label, so the only way to learn the eel is to ask the counter for the species and the country of origin.
Species goes first (Japanese, American or European eel), then the country that farmed it. If neither answer comes, go with anago or skip eel. The order matters because the IUCN category follows the species, not the farm.
The CoP20 vote left American eel, the species that dominated imports in the 2025 Fisheries Science retail study, outside Appendix II, so no CITES permit documents its trade. A counter cannot run the DNA test that separated the species in that study, which makes the staff answer the check a diner has.
This advice was last verified in October 2026. It changes if fully farmed eel moves past trial sales or Japan requires species labels on retail eel.
