Fauna
Species

Japanese Eel

Anguilla japonica

Also known as Nihon Unagi, Japanese Freshwater Eel

Japanese eels embark on an extraordinary multi-thousand-kilometer journey from their freshwater river homes to spawn in the deep waters near the Mariana Trench. Their slender, snake-like bodies are coated in a protective mucus layer that allows them to travel overland through wet grass to bypass river obstacles. As they mature from translucent glass eels into dark, silver-bellied adults, they play a vital role as nocturnal predators in East Asian river ecosystems.

CatadromousMigratory
Japanese Eel reference1 / 2
opencage / CC BY-SA 2.5 · CC BY-SA 2.5
—observations
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—peak records
EndangeredConservation statusIUCN Red List categoriesLCNTVUENCREWEXEndangeredRed List categories, explained →
Key facts
Diet & preyFreshwater shrimp, Aquatic insects, Small crabs
Predators
  • Large predatory fish
  • Herons
  • Humans
ThreatsOverfishing of glass eels, river dams blocking migration, and habitat loss
HabitatsRivers, estuaries, lakes, and deep ocean spawning grounds
Life span5 to 15 years
Classification
  1. FamilyAnguillidae
  2. SpeciesAnguilla japonica
Range & activity
Range data is not available yet.
Safe observation
Interaction riskLow
  1. Low
  2. Moderate
  3. High
  4. Very high
Why interaction risk is low
Can deliver a sharp bite if handled; observe from a safe distance without touching.
What to notice
Look for a snake-like body with a continuous dorsal, caudal, and anal fin, typically dark olive to silver-grey.
Support conservation
Avoid disturbing migrating eels, support river restoration projects, and never harvest wild individuals.
Responsible observation
  • Nighttime Spotting: Use a red-light flashlight to observe these nocturnal hunters foraging along riverbanks without startling them.
  • Support Conservation: Avoid purchasing wild-caught glass eels or uncertified eel products to help reduce pressure on wild populations.
  • Report Sightings: Document any encounters in local waterways on citizen science platforms to assist researchers tracking their range.
Related species
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