抄録
Indonesia has the sixth largest Exclusive Economic Zone (EEZ) in the world. Although fisheries offshore of the Indonesian EEZ are active and produce high levels of products, several illegal, unreported and unregulated (IUU) fishing activities are also recognized in this region. IUU fishing activities are monitored and reported by the Ministry of Marine Affairs and Fisheries of Indonesia (Kementerian Kelautan dan Perikanan in Indonesian, referred to as the ‘KKP’) and its institute, i.e., the Institute of Information Management of Marine and Fisheries Resources (Balai Pengelolaan Informasi Sumber Daya Kelautan dan Perikanan, the ‘BPISDKP’) with the use of satellite data. PALSAR-2, the Japanese synthetic aperture radar (SAR) sensor on the Japanese satellite ALOS-2, has a ScanSAR Normal Mode (PALSAR-2/ScanSAR) which has its observation area as 350.5 km×355 km, and PALSAR-2/ScanSAR has been found to be effective for monitoring wide offshore areas of Indonesia. However, the average size of fishing vessels is <20 m, which is smaller than the 50-m resolution of PALSAR-2/ScanSAR. The present study analyzed and confirmed the abilities of PALSAR-2/ScanSAR for IUU fishing detection. Authors brought GNSS receivers and took a 17.6-m-long vessel to the northern sea of West Bali, Indonesia on the date of PALSAR-2/ScanSAR observation. Using the observation from the GNSS signal collection on the vessel as the ground truth and the vessel observation by PALSAR-2 sensor, authors also analyzed the data product and the GNSS signals to detect the vessel. The results revealed that the fishing vessel was detected as a single pixel. Our findings confirmed that (i) PALSAR-2/ScanSAR has useful and effective abilities for monitoring small-scale fishing activities offshore, and (ii) PALSAR-2/ScanSAR can be used for practical monitoring operations in Indonesian marine waters. This study thus provides one example ensuring the abilities of PALSAR-2/ScanSAR, and authors note that improvements of the accuracy of PALSAR-2/ScanSAR could be achieved by conducting observations under various environmental conditions in order to enhance its capacities for monitoring IUU fishing activities in Indonesian oceans.
