The Mediterranean is emerging as a high-risk environment for large whales, with collisions with commercial and passenger ships among the leading human-caused threats to endangered fin whales and sperm whales.
Although the Mediterranean accounts for less than 1% of the world’s ocean surface, it carries around 15% of global shipping activity. Dense maritime traffic creates a particularly dangerous environment where shipping routes overlap with critical whale habitats.
Nearly 2,800 large ships above lethal speed threshold
The scale of the risk is highlighted by shipping speeds. According to an analysis of Global Fishing Watch data by Mongabay and Magma Magazine, nearly 2,800 different large vessels travelled at speeds above 15 knots, or around 28 km/h, inside key whale habitats in the Mediterranean during 2025.
Research cited by the report indicates that collisions with whales at speeds above 15 knots are almost always fatal. At any given time, around 30 vessels were travelling above that threshold in the areas studied.
The full scale of whale deaths remains unknown. Many collisions in open waters go undetected, while some carcasses sink before reaching the coast.
A 2023 study conservatively estimated that ship strikes kill an average of 16.6 fin whales each year in the Mediterranean. Researchers consider this figure higher than the level of mortality the population can sustain while recovering.
Around 300 sperm whales remain in eastern Mediterranean
The situation is particularly significant for Greece and the eastern Mediterranean, where the Hellenic Trench is one of the most important habitats for sperm whales.
According to Simone Panigada, president of the Tethys Research Institute, only around 300 sperm whales are estimated to remain in the eastern Mediterranean.
Scientists say that slightly shifting some shipping routes further offshore in parts of the Hellenic Trench could significantly reduce the risk of collisions.
Greece develops system to detect whales
Changing shipping routes is more difficult in the Kythira Strait because of heavy maritime traffic. A different approach is being developed there.
The Greek government, together with the shipping industry and environmental organisations, is promoting the SAvE Whales system. It uses underwater hydrophones to passively detect the distinctive clicks of sperm whales and warn passing vessels when whales are present.
The system was tested in a pilot programme in 2019-2020 and, according to Mongabay, is scheduled to begin operating in 2028.
Speed reductions offer another solution
Reducing vessel speeds is another measure being considered. The International Maritime Organization has already recommended speeds of 10-13 knots in a large protected area in the north-western Mediterranean.
However, an OceanCare analysis found that more than 80% of voyages by six major categories of commercial vessels in the area during 2023 and 2024 were made at speeds above 10 knots.
The conflict between whale protection and the demands of commercial shipping remains difficult to resolve. Lower speeds can affect arrival times, routes and port operations.
For scientists, however, the stakes are clear: some of the Mediterranean’s last large sperm and fin whales are trying to survive in one of the world’s busiest maritime environments.
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