Decreasing Trend of Great White Shark <i>Carcharodon carcharias</i> Records in the Mediterranean: A Significant Population Loss or Shifts in Migration Patterns?

The Mediterranean subpopulation of great white sharks (Carcharodon carcharias) is elusive and likely in decline, though long-term trends remain uncertain due to opportunistic record-keeping, misidentifications, and changing observation effort. We investigated whether spatial changes in shark occurrences during the 21st century correspond with shifts in Atlantic bluefin tuna (Thunnus thynnus) distribution and habitat conditions. We compiled geographically validated sighting and capture records from 1900 onward, mapped 20th- and 21st-century hotspots, and overlaid these with bluefin tuna potential habitat and long-term sea surface temperature (SST) data. Results reveal a clear redistribution of great white shark hotspots: historic coastal focal areas (e.g., Balearic Islands, Maltese Islands, eastern Adriatic, Sea of Marmara) have diminished or disappeared, while offshore zones (southern Strait of Sicily-Gulf of Gabes) and the Aegean coast of Turkey have emerged as contemporary hotspots. These patterns appear to align closely with shifts in tuna feeding grounds and cooler SST (<18 degrees C). We highlight limitations in using opportunistic and citizen-reported data due to detection biases and misidentifications, underscoring the need for models that correct detectability. Our findings are consistent with the hypothesis of a link between predator distribution, prey dynamics, and changing ocean conditions, and point toward targeted strategies for future conservation and monitoring of this apex predator in a warming Mediterranean.