Abstract:Illegal, unreported, and unregulated (IUU) fishing seriously affects various aspects of human life. However, current methods for detecting and monitoring IUU activities at sea have limitations. While Synthetic Aperture Radar (SAR) can complement existing vessel detection systems, extracting useful information from SAR images using traditional methods, especially for IUU fishing identification, poses challenges. This paper proposes a deep learning-based system for detecting fishing activities. We implemented this system on the xView3 dataset using six classical object detection models: Faster R-CNN, Cascade R-CNN, SSD, RetinaNet, FSAF, and FCOS. We applied improvement methods to enhance the performance of the Faster R-CNN model. Specifically, training the Faster R-CNN model using Online Hard Example Mining (OHEM) strategy improved the Avg-F1 value from 0.212 to 0.216, representing a 1.96% improvement.