Depth
Aulopus · Bony Fish

Royal Flagfin

Aulopus filamentosus

50-200m
Depth Range
40cm
Max Size
Mediterranean
Distribution
50-200m
Depth Range
40cm
Max Size
Deep reef
Habitat
Carnivore
Diet
Solitary
Social
LC
IUCN Status
Rare
Sighting Likelihood
Kingdom Animalia
Phylum Chordata
Class Actinopterygii
Genus Aulopus
Species filamentosus

Bony Fish

Identification & Biology

  • IdentificationSmall, elongated body with a distinctively large, sail-like dorsal fin that extends into a long filament, especially in males. Reddish-pink body with darker bars. Large eyes.
  • SizeUp to 44 cm total length, commonly 15 to 25 cm.
  • Social HabitUsually solitary or in pairs on the seabed.
  • HabitatSandy and muddy bottoms from moderate to great depths.
  • Depth30 to 1,000 m, most common between 50 and 300 m.
  • Feeds OnSmall crustaceans and fish found on or near the seabed.
  • DistributionEastern Atlantic from the Bay of Biscay to South Africa, including the Mediterranean Sea.
  • DescriptionA beautiful deep-water fish named for its spectacular, elongated dorsal fin. It sits on sandy bottoms at depths beyond most recreational dives and is rarely encountered. The tall dorsal fin is thought to play a role in courtship displays.

Range

Habitat & Distribution

A benthic species found on rocky and mixed substrates along the continental shelf and upper slope in the Mediterranean. Typically encountered between 50m and 200m, occasionally shallower.

Where Malta divers have spotted this species

Loading…

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

Detail

Preferred Environment

Prefers hard substrates and rocky outcrops in deeper water where it can rest motionless on the seabed. Occasionally encountered by technical divers on deeper Mediterranean walls.

Encounter Tips

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

Royal Flagfin species card

Biology

Behaviour & Diet

Feeding Strategy

An ambush predator that rests on the seabed and strikes at passing small fish and crustaceans with rapid lunges.

Ambush predator

Reproduction

Spawns in deep water. Females produce pelagic eggs that develop in the water column. Relatively little is known about its reproductive biology.

Deep spawner

Behaviour & Defence

Relies on cryptic colouration and motionless behaviour to avoid detection on the seabed. Flees rapidly when disturbed.

Cryptic ambush

Dive with diveshack

Where to Encounter in Malta

Dive sites where Aulopus filamentosus may be encountered will be added as sighting data is collected.

IUCN Red List Least 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
diveshack Mediterranean Marine Life guide