Depth
Prionace · Sharks & Rays

Blue Shark

Prionace glauca

0-350m
Depth Range
3.8m
Max Size
Mediterranean
Distribution
0-350m
Depth Range
3.8m
Max Size
Pelagic
Habitat
Carnivore
Diet
Solitary
Social
NT
IUCN Status
Rare
Sighting Likelihood
Kingdom Animalia
Phylum Chordata
Class Elasmobranchii
Genus Prionace
Species glauca

Elasmobranch

Identification & Biology

  • IdentificationA slender, graceful shark with a long conical snout, large round eyes, and exceptionally long, narrow pectoral fins. Vivid indigo-blue on the back, bright blue on the flanks, and white underneath. One of the most recognisable open-ocean sharks.
  • SizeCommonly 1.8 to 2.5 m. Maximum recorded length 3.8 m and weight around 205 kg.
  • Social HabitOften travels in groups loosely segregated by sex and size. Highly migratory, with tagged individuals crossing entire ocean basins. One of the most wide-ranging shark species.
  • HabitatOpen ocean (pelagic), from the surface to deep water. Occasionally approaches coastlines where the continental shelf is narrow or near underwater canyons.
  • Depth0 to 600 m. Spends most time in the upper 150 m but dives deeper when hunting.
  • Feeds OnSquid (primary prey), small pelagic fish (mackerel, herring, sardines), octopus, and occasionally seabirds and whale carcasses.
  • DistributionWorldwide in temperate and tropical oceans. Present throughout the Mediterranean, including Maltese offshore waters.
  • DescriptionPrionace glauca is the most widespread and abundant open-ocean shark, yet it is also one of the most heavily fished, primarily as bycatch in longline fisheries targeting tuna and swordfish. In the Mediterranean, blue sharks are regularly caught but rarely seen by divers because they inhabit open water far from shore. Listed as Near Threatened globally by the IUCN, with Mediterranean populations assessed as Critically Endangered.

Range

Habitat & Distribution

The most wide-ranging shark in the Mediterranean, found throughout the basin in open pelagic waters. Blue sharks are highly migratory and follow seasonal movements of prey, covering enormous distances across the sea.

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

Primarily an open-ocean species preferring cool to temperate waters above the thermocline. In the Mediterranean, it ranges from the surface to several hundred metres depth and is most often encountered well offshore.

Encounter Tips

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

Blue Shark species card

Biology

Behaviour & Diet

Feeding Strategy

Feeds opportunistically on squid, pelagic fish such as mackerel and sardines, and occasionally on seabirds and smaller sharks. Often scavenges from fishing nets and longlines.

Opportunistic hunter

Reproduction

Viviparous with a yolk-sac placenta. Litters are large, ranging from 25 to over 100 pups. Females have evolved thickened skin -- up to three times thicker than males -- to withstand mating bites.

Viviparous

Behaviour & Defence

Curious and may approach divers closely but is not typically aggressive. When threatened, it moves away with powerful strokes of its long tail.

Curious but cautious

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Where to Encounter in Malta

Dive sites where Prionace glauca may be encountered will be added as sighting data is collected.

IUCN Red List Near Threatened

Conservation Status

This species is assessed as Near Threatened 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