Japanese eel
Anguilla japonica
Also known asUnagi
Water parameters
Minimum tank: 500 L per individual at harvest size.
Feed and growth
- Feed protein
- 45% target
- Daily feed (warm)
- 1.50% of body weight
- Daily feed (cool)
- 0.50% of body weight
- Max density
- 40 g per litre
A 500 g adult eats about 7.5 g of feed per day at optimum. 10 fish at adult size: ~75 g daily.
Legality
Rules vary by jurisdiction and change over time. Verify with your local fisheries or wildlife authority before stocking.
| Jurisdiction | Status | Notes |
|---|---|---|
| jp | permit required | Glass eel fishing licenses and aquaculture permits required; catch quotas tightening annually verified 2026-05-14 |
| us-general | check local regulations | Not established in US waters; import of live eels is regulated by USFWS verified 2026-05-14 |
Unlisted jurisdictions default to "check local regulations".
Origin and habitat
Anguilla japonica is a catadromous eel of East Asia, found in fresh, brackish, and coastal waters of Japan, Korea, China, Taiwan, and Vietnam. Its life cycle mirrors the European eel's: mature silver eels leave fresh water in late summer and autumn and swim thousands of kilometres to spawn west of the West Mariana Ridge in the western North Pacific, around 13 to 15 degrees north, where larvae hatch and ride the North Equatorial and Kuroshio currents back to East Asian coasts, arriving as glass eels that run upstream. It is one of Japan's most prized food fish, grilled as unagi, a dish tied closely to summer tradition. Wild stocks have fallen sharply, and the IUCN lists the species as Endangered, citing overfishing, habitat loss, migration barriers, pollution, and shifting ocean currents. Eel farming is a large industry, on the order of a few hundred thousand tonnes a year with the great majority produced in China, but it still depends on wild-caught glass eels: although Japanese researchers closed the full life cycle in the lab in 2010, raising eels through to a new generation, mass production at a workable cost has not been reached.
Climate and outdoor ponds
- Climate
- temperate (handles seasonal swings)
- USDA zones
- 6–11 (winter low around -23°C or warmer)
- Heating needed
- yes
- Cooling needed
- no
Care notes
A high-value fish grown across East Asia for the premium unagi market. Glass eels are netted on their upstream run, mostly November to April, then raised in heated ponds or recirculating systems at 25–30°C and grown to a market size of 200–300 g over twelve to eighteen months; production is on the order of several hundred times the weight of the glass eel seed. Feed conversion on a high-protein eel pellet of 45 to 50 percent runs about 1.5 to 2.0, with intensive stocking of 30 to 80 g/L. The same conservation issue as the European eel applies: every glass eel comes from an endangered wild stock, and prices are extraordinary, running from thousands into the tens of thousands of dollars per kilogram in scarce years. Finished unagi sells at a steep premium. For aquaponics the eel is in principle compatible, but glass eel cost, conservation concerns, and the specialized skill eel culture demands put it out of reach for home systems; it is relevant mainly to commercial East Asian eel farms looking at waste-stream integration, and a growing share of producers are moving to closed recirculating systems.