Depth
Ruvettus · Bony Fish

Oilfish

Ruvettus pretiosus

100-800m
Depth Range
300cm
Max Size
Mediterranean
Distribution
100-800m
Depth Range
300cm
Max Size
Bathypelagic
Habitat
Carnivore
Diet
Solitary
Social
LC
IUCN Status
Low
Sighting Likelihood
KingdomAnimalia
PhylumChordata
ClassActinopterygii
GenusRuvettus
Speciespretiosus

Bony Fish

Identification & Biology

  • IdentificationLarge, elongated body that is dark brown to black with a metallic sheen. Skin is smooth and oily. Two dorsal fins. Large eyes suited to deep-water life. Body contains indigestible wax esters instead of normal fat.
  • SizeUp to 200 cm total length, commonly 80 to 150 cm.
  • Social HabitSolitary or in small groups in deep water.
  • HabitatDeep open water, mesopelagic to epipelagic zone. Occasionally comes near the surface at night.
  • Depth100 to 800 m, occasionally shallower at night.
  • Feeds OnFish, squid, and crustaceans caught in deep water.
  • DistributionWorldwide in tropical and temperate seas, including the Mediterranean Sea.
  • DescriptionA deep-water predator that is rarely seen by divers. The oilfish contains high levels of indigestible wax esters in its flesh, which can cause digestive problems if eaten. Despite this, it is sometimes sold as butterfish. It is occasionally caught by deep-sea longline fisheries in the Mediterranean.

Range

Habitat & Distribution

Inhabits deep oceanic waters from 100 to 800 metres, occasionally deeper. Occurs throughout the Mediterranean in deep basins and along continental slopes. Very occasionally washed ashore or caught as bycatch in Maltese waters.

Where Malta divers have spotted this species

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Sightings are logged by divers using our What Did You See? dive-log tool. View the full live sightings map.

Detail

Preferred Environment

Deep open water above continental slopes and seamounts. Performs vertical migrations, approaching mid-water zones at night to feed.

Encounter Tips

Best approached slowly and calmly. Avoid casting shadows directly over the animal. Neutral buoyancy and patience increase encounter success significantly.

Oilfish species card

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Where to Encounter in Malta

Dive sites where Ruvettus pretiosus may be encountered will be added as sighting data is collected.

IUCN Red ListLeast Concern

Conservation Status

This species is assessed as Least Concern on the IUCN Red List. Mediterranean populations face ongoing pressure from fishing activity, habitat degradation, and climate-driven changes.

Source: IUCN Red List
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