Blue Shark

What is blue shark?

The blue shark (Prionace glauca) is a shark belonging to the family Carcharhinidae that inhabits tropical and temperate oceans worldwide. It is easily recognized by its deep-blue coloration, which contrasts with a pure-white belly, and its slim body featuring a pointed snout and long, slender pectoral fins.¹²

Typically measuring 1.7 to 2.2 meters (5.6 to 7.2 feet) in length, some individuals can grow up to 4 meters. These sharks are opportunistic predators, feeding on fish, squid, and crustaceans, and they have been known to scavenge whale carcasses. While not considered aggressive, they are potentially dangerous to humans and have been implicated in unprovoked attacks.¹²

Currently listed as near threatened by the IUCN, blue shark populations face significant pressure from commercial fishing bycatch and the sportfishing industry.¹

How do blue sharks migrate across the ocean?

Blue sharks (Prionace glauca) are known for their extensive movements across the ocean, which are primarily driven by feeding requirements, reproductive activities, or seasonal environmental changes. These sharks are capable of transoceanic travel, with documented instances of individuals crossing the southern Atlantic Ocean.³

While the full extent of their migratory patterns is still being researched, scientists have gained significant insights through the use of satellite tagging technology. These tags beam signals to orbiting satellites whenever a shark surfaces, allowing researchers to track their roaming behavior, north-south movements, and long-distance transoceanic journeys. Like other large marine vertebrates, these movements are essential for the species to navigate between areas that provide optimal conditions for survival and reproduction.³⁴

What makes the blue shark’s skin different from other sharks?

The blue shark (Prionace glauca) does not possess a unique skin structure that fundamentally differs from other sharks. Like most sharks, its skin is covered in scales known as dermal denticles, which are structurally minute teeth composed of a hollow cone of dentine covered by a hard, enamel-like substance called vitrodentine.¹

However, there is a notable difference in skin thickness between the sexes of this species. The blue shark is sexually dimorphic, meaning adult females possess thicker skin than males. This adaptation is believed to be a protective measure against the biting behavior often exhibited by males during mating rituals.⁵

Why are blue sharks considered ‘near threatened’ by conservationists?

The International Union for Conservation of Nature (IUCN) classifies the blue shark (Prionace glauca) as near threatened primarily due to significant population declines observed in the Atlantic and Indian oceans since the 1970s.¹

These declines are largely driven by the following factors:

• Bycatch: Blue sharks are frequently caught unintentionally by commercial fishing fleets using nets and longline hooks intended for other species. Once captured, these sharks are often harvested for their meat and fins.¹⁶
• Commercial Demand: Despite global efforts to curb shark finning, the trade in shark products continues to exert pressure on populations.¹⁶
• Sportfishing: While the sportfishing industry often practices catch-and-release, the stress and injuries sustained during these encounters can sometimes result in the death of the shark.¹

Protecting these predators is essential, as they play a vital role in maintaining the health of marine ecosystems.⁶