This thesis presents a spatio-temporal analysis of fishing activity targeting large pelagic fishes (LPF) in the Mediterranean Sea from 2015 to 2024. Using vessel tracking data from the Automatic Identification System (AIS) fishing effort by drifting longliners and tuna purse seiners, the two main gear types targeting bluefin tuna, swordfish, and albacore tuna, was assessed.
Persistent fishing hotspots were identified around the Balearic Islands, Sicily, the Adriatic, Cyprus, and south of Malta, aligning with known LPF spawning and feeding grounds. Purse seine activity peaked in spring, driven by bluefin tuna migration, while longline fishing showed broader seasonality with a summer peak. The Balearic purse seine hotspot shifted over time, possibly tracking oceanographic variability in bluefin spawning areas. Overall, fishing grounds remained spatially stable, though longline activity expanded seasonally, potentially due to increases in temperature caused by climate change.
AIS data was biased towards larger EU-flagged vessels and did not fully capture non-EU fleets. Despite this, it provides a valuable source of information on effort distribution and potential overlap with sensitive habitats. This study supports the use of AIS in monitoring LPF fisheries and highlights the importance of improving registry transparency and combining data sources to inform ecosystem-based management in the Mediterranean.
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