Abstract
Marine protected areas (MPAs) are expanding worldwide, but industrial fishing within their boundaries remains poorly understood. By combining vessel Global Positioning System data with satellite imagery, we detected industrial fishing in 47% of coastal MPAs worldwide between 2022 and 2024, with two-thirds of vessel detections (67%) untracked by public monitoring. These untracked vessels were most prevalent (80%) in MPAs with the most restrictive management category, which aims to prohibit all extractive activities. The presence and density of fishing vessels were mainly driven by the size and remoteness of MPAs rather than their management category itself. Including untracked vessels increased estimated fishing effort within MPAs by 28%, to an average of 4 hours per square kilometer per year. These results highlight the continued presence of industrial fishing vessels in MPAs and an important gap in our understanding of fishing pressure on protected areas worldwide.