Giant moray (Gymnothorax javanicus)

Classification (WoRMS)

Full classification as recorded by WoRMS: Kingdom: Animalia · Phylum: Chordata · Class: Teleostei · Order: Anguilliformes · Family: Muraenidae · Genus: Gymnothorax.

Accepted name: Gymnothorax javanicus · Authority: (Bleeker, 1859) · Taxonomic status: accepted · AphiaID: 217502.

Synonyms and superseded combinations recorded for this taxon: Gymnothorax javonica (Bleeker, 1859); Lycodontis javanicus (Bleeker, 1859); Muraena javanica Bleeker, 1859.

Source: World Register of Marine Species (WoRMS) — https://www.marinespecies.org/aphia.php?p=taxdetails&id=217502 (CC BY 4.0). Accessed 2026-09-23.

Biology and life history (FishBase)

Measured values published by FishBase for Gymnothorax javanicus. Only fields the database actually holds for this species are shown; these are database values, not aquarium guidance.

Maximum length: 300 cm · Depth range: 0–50 m · Habitat zone: reef-associated · Body shape: eel-like · Vulnerability index: 90 of 100 · Fishery importance: subsistence fisheries · Aquarium trade: public aquariums.

FishBase notes: Found in lagoon and seaward reefs. Commonly seen species along deep drop-offs and slopes in Indonesian waters (Ref. 48635). Benthic (Ref. 58302). Juveniles more secretive and occur on intertidal reef flats (Ref. 37816). It feeds primarily on fishes and occasionally on crustaceans. This is the largest Indo-Pacific moray eel (Ref. 30404), perhaps reaching 3 m in length. Because of its position at the top of the reef's food chain it is often ciguatoxic. Attacks humans when provoked (Ref. 3132). Minimum depth reported taken from Ref. 10713. Solitary in reef holes (Ref 90102).

Source: FishBase species summary (SpecCode 6380) — https://www.fishbase.se/summary/Gymnothorax-javanicus.html (CC BY-NC 3.0 — non-commercial use only). Accessed 2026-09-23.

Distribution and occurrence records (GBIF)

5,237 georeferenced occurrence records for Gymnothorax javanicus are published through GBIF from 68 countries or marine areas. The map above plots 382 distinct locations from a sample of 3,000 records, omitting 33 inland records that carry an institution's coordinates rather than a collection site; it shows where the species has been observed and reported, not a modelled range.

Most records by country or area: Egypt (1,214); Indonesia (629); Australia (454); French Polynesia (439); Maldives (366).

The full country table, WoRMS marine regions and the sampling notes are on this species' Distribution page.

Source: GBIF Occurrence Search (taxonKey 2403808) — https://www.gbif.org/occurrence/search?taxon_key=2403808&has_coordinate=true (records CC0 / CC BY); WoRMS distribution records (MarineRegions) — https://www.marinespecies.org/aphia.php?p=taxdetails&id=217502 (CC BY 4.0); Natural Earth 110m basemap — https://www.naturalearthdata.com/ (public domain). Accessed 2026-09-23.

Conservation status (IUCN Red List)

The IUCN Red List assesses Gymnothorax javanicus (Bleeker, 1859) as Least Concern (code LC). No trend, population estimate or threat analysis is given here, because none is available from this source without the Red List API; follow the source link for the full assessment, including its date.

Source: IUCN Red List of Threatened Species (taxon 195741) — https://www.iucnredlist.org/species/195741/0; GBIF IUCN Red List category endpoint (taxonKey 2403808) — https://api.gbif.org/v1/species/2403808/iucnRedListCategory. Accessed 2026-09-23.

Description and natural history (Wikipedia)

As the name suggests, the giant moray is a large eel, reaching up to a little over 3m (10 feet) in length and 30 kg in weight. Its elongated body is brownish in color. While juveniles are tan in color with large black spots, adults have black specks that grade into leopard-like spots behind the head.

The giant moray is widespread in the Indo-Pacific region, being found from eastern coast of Africa, Red Sea included, to the Pitcairn group, Hawaiian Islands and also Polynesia, north to southern Japan and south to New Caledonia, Fiji and the Austral Islands.

It lives in lagoons and on the outer slopes of coral reefs. During the day, it sits sheltered in crevices between 1 and 50 meters deep.

The giant moray is carnivorous and nocturnal, hunting its prey within the reef. It is known to engage in cooperative hunting with the roving coral grouper (Plectropomus pessuliferus). These two fish species are complementary hunters: While the eel hunts in the reef, it may scare prey up and out of the reef, leaving them to be eaten by the grouper. Similarly, the grouper hunting above the reef may cause prey to attempt to seek refuge in the reef, where the moray may ambush them.

The giant moray mainly feeds on fish and occasionally on crustaceans. This moray eel was recently identified as a natural predator of the lionfish (Pterois miles) in its native habitat in the Red Sea. A mature giant moray has few natural predators, although it may compete for food with reef-dwelling sharks. Cleaner wrasses are commonly found in its presence, cleaning the interior of its mouth.

Gymnothorax javanicus have been shown to have very small optic tectum volumes, indicating that they primarily hunt by smell rather than vision.

This species may be hazardous to people. Being at the top of the food chain, it has been known to exhibit biomagnification of harmful ciguatera toxins. Eating a giant moray, especially the liver, can thus cause illness, coma, or even death. While this moray may bite if threatened, cornered or in the presence of food, it is not usually aggressive.

Source: Wikipedia: Giant moray — https://en.wikipedia.org/wiki/Giant_moray (CC BY-SA 4.0). Accessed 2026-09-23.