The untracked industrial fishing fleet of the world's marine protected areas

Marine protected areas (MPAs) are expanding worldwide, but the extent of fishing pressure within them is poorly understood. We conducted a global assessment of industrial fishing presence, density and activity in coastal MPAs from 2022 to 2023, using vessel tracking and satellite imagery data. Industrial fishing vessels were detected in 43% of MPAs, with no effect of protection level on their presence. Non-publicly tracked vessels, the hidden part of fishing fleets, accounted for the highest proportion of detections (81%) in the strictest MPAs (IUCN Category I). Including untracked vessels increased the estimated fishing effort within MPAs by 36%, to an average of 2.36 hours/km²/year. These results highlight systemic challenges and the widespread presence of industrial fishing vessels, including untracked vessels, within MPAs worldwide.