Published On 5/6/2026
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Last update: 17:23 (Mecca time)
New scientific examinations show that nearly half of the fish species in the Mediterranean have changed their range over the past 20 years, due to climate change.
These habitat changes have included the migration of some marine species from their original habitats in unexpected directions, which will have a significant impact on biodiversity and ecosystems in the future.
The semi-enclosed Mediterranean Sea is warming at a rate two to three times faster than the world’s oceans. In the face of this climate crisis, scientists expected a mass and organized migration of marine organisms northward or toward the depths in search of cooler waters.
However, the observed reality proved that this migration was more complex and surprising, according to two pioneering studies conducted by the Spanish Institute of Oceanography (IEO-CSIC) and the Balearic Islands Ocean Center (COB-IEO).
Both studies were based on long-term data drawn from research projects funded by the European Commission and Spanish government bodies.
Wider habitat and less food for swordfish
The first study, recently published in the journal Progress in Oceanography, analyzed how environmental shifts associated with climate change are modifying the breeding habitat of the swordfish, scientifically known as Sivaea gladias, in the western Mediterranean.
This species takes the areas surrounding the Balearic Islands as its main breeding area in waters with a salinity of 37.5 and a temperature of more than 24 degrees Celsius. It is classified as an endangered species on the Red List of the International Union for Conservation of Nature, and its population in the Mediterranean Sea is witnessing a historic decline.
The study revealed that rising water temperatures accelerated the maturation of swordfish larvae, advancing the start of reproduction by half a day annually between 2004 and 2022, expanding the area in which the early stages of larval life can develop.
However, researchers point out that this expansion of habitats does not actually indicate that the environment has become more suitable for life to flourish; Concurrent with the rise in temperature, chlorophyll concentration has declined sharply in the Western Basin since 1998, a key indicator of the state of phytoplankton and marine productivity at the base of the food chain. The larvae now have more space to hatch, but they find much less food to survive.
Migrations in unexpected directions
The swordfish was not the only marine creature whose habitats were affected by climate change in the western Mediterranean. The study, published in the scientific journal Ecological Indicators, revealed, by studying 102 species of benthic fish and invertebrates over a period of 25 years (1994-2019) along the Spanish coast, that nearly half of them (42 species) had significantly changed their geographical distribution. What is most surprising is that a large percentage of these species migrated south and southwest, heading, contrary to what scientists previously expected, towards areas witnessing more severe rates of climate change and higher temperatures.
Marina Sanz-Martin, a postdoctoral researcher at the Ocean Center of the Balearic Islands, explains this puzzling phenomenon, saying in a statement to Al Jazeera Net: “We found that nearly half of the species of commercial value in the Mediterranean have changed their distribution over the past two decades, and although these changes vary from one species to another, they are mostly characterized by a trend towards the south and southwest of the Mediterranean.”
“These species shifts can be explained by the local climate change speed index, which measures the direction and speed at which species must move to maintain the initial or preferred temperature conditions of their habitats,” the study’s lead author explained.
The results also show that the largest shifts in geographic distribution are closely associated with regions experiencing the fastest warming. As a result, many species moved their population centers to the southwest.
For example, while the angler fish (Lovius bodigasa), which prefers cold waters, dives vertically towards the depths of the ocean, the starfish (Raja asterias), which prefers relatively warm temperatures, heads towards the southern Mediterranean.
The authors of both studies stressed the need for a comprehensive reform of marine resource management policies, through the development of adaptive management strategies capable of responding to observed changes in the geographical distribution of marine organisms and exploited fish populations in the Mediterranean Sea, affected by climate change.
The researchers also emphasized that preserving fisheries and marine biodiversity requires incorporating these sub-regional climate change acceleration pathways and trophic shifts into future plans to revive fisheries and protect marine food supplies.
