Why Great White Sharks Are Vanishing From the Mediterranean

A Ghost in the Blue

In April 2023, fishermen off the Spanish Mediterranean coast hauled up an unexpected catch: a juvenile great white shark, roughly two metres long. The encounter set off a scientific investigation stretching back 160 years — and reignited urgent questions about one of the ocean's most iconic predators. The Mediterranean's great white sharks are still here. But barely.

A Population Born From a Wrong Turn

Most people assume Mediterranean great whites are simply Atlantic sharks that wander through the Strait of Gibraltar. The genetics tell a far stranger story. Research funded by the Save Our Seas Foundation found that the Mediterranean population descends not from Atlantic ancestors, but from Pacific Australian and New Zealand populations — separated from their origins by roughly 450,000 years.

The leading theory is that during an interglacial warming period, sharks following unusually warm currents entered the Mediterranean through what is now the Strait of Gibraltar and then became trapped as conditions shifted. Over hundreds of thousands of years, they evolved into a genetically distinct subpopulation with little or no ongoing migration from the Atlantic — making them uniquely isolated, and uniquely fragile.

How Many Remain?

The honest answer: scientists are not sure. The IUCN Red List estimates no more than 250 mature individuals survive in European and Mediterranean waters, and classifies the regional population as Critically Endangered — the highest threat category before extinction in the wild.

A 2025 review of records spanning 160 years documented a 61% decline in sightings since the 1970s. In the decade prior to that study, fewer than four confirmed sightings were recorded — compared to roughly ten per year in the late 1980s and early 1990s. The species is, as one landmark paper put it, "rare, but persistent."

Where They Hide

The Sicilian Channel — the shallow stretch of sea between Sicily and Tunisia — is the closest thing the Mediterranean's great whites have to a home base. Research expeditions using environmental DNA (eDNA) sampling, underwater video surveys, and fishing operations confirmed white shark presence at four sites in this area. The region corresponds closely with bluefin tuna spawning aggregations each May and June, suggesting the sharks follow their prey into these waters seasonally.

The Strait of Sicily is also believed to function as a nursery area: the place where females give birth and juveniles spend their early years. The 2023 juvenile catch, along with earlier pup sightings, supports the idea that reproduction is still occurring — though at what rate remains unknown.

Why They Are Disappearing

Several forces are converging to push the population toward collapse:

• Overfishing and bycatch. The Mediterranean is the world's most intensively fished sea, with an estimated 62% of fish stocks categorised as overfished. White sharks are not targeted directly, but they die in nets, on longlines, and in trawls. Historically, they were also deliberately hunted after publicised attacks.
• Prey depletion. Mediterranean bluefin tuna and monk seals — key food sources — have themselves been severely reduced by centuries of human exploitation. A predator without prey cannot survive.
• Genetic isolation. With no meaningful immigration from Atlantic populations, any loss of individuals cannot be replenished. The founding population was already genetically narrow, creating a bottleneck that limits resilience to disease, environmental change, or further hunting pressure.
• Pollution. The Mediterranean accumulates heavy metals, plastics, and persistent organic pollutants at high concentrations. As apex predators, great whites accumulate these toxins through bioaccumulation across the food chain.

The Puzzle Scientists Are Trying to Solve

Despite their iconic status, Mediterranean great whites remain poorly understood. Unlike populations in California or South Africa, they have no known aggregation sites where researchers can observe and tag them reliably. A major multi-institution expedition ran 159 eDNA water samples and nearly 360 hours of underwater video survey in the Sicilian Channel — without a single direct sighting. The sharks were confirmed present, but critical data on population size, migration patterns, and reproductive rates remains elusive.

Researchers are now deploying citizen science networks, satellite tagging of accidentally captured individuals, and AI-assisted eDNA analysis to build a clearer picture before it is too late.

Why It Matters Beyond the Shark

Great white sharks are apex predators — animals whose presence regulates the entire food web beneath them. Remove them, and populations of their prey species explode, cascading disruptions through ecosystems that humans depend on for fisheries and coastal economies. The Mediterranean's great whites are not merely a conservation curiosity. They are an indicator of the overall health of one of Earth's most historically over-exploited seas.

The juvenile shark hauled from the water in 2023 was released alive. Whether the population it represents can survive the pressures closing in on it is one of marine biology's most pressing open questions.