Spatio-Temporal Analysis of Thermal Fronts and Indian Ocean Dipole Influence on Yellowfin Tuna (Thunnus albacares) Productivity in Palabuhanratu, Indonesia

Thermal fronts are oceanographic features often associated with potential fishing zones for pelagic species such as the yellowfin tuna (Thunnus albacares). This study analyzed the spatial and temporal dynamics of thermal fronts and their relationship with thermal front intensity, sea surface temperature (SST), and the Indian Ocean Dipole (IOD) on the yellowfin tuna catch in Palabuhanratu waters from 2016 to 2020. The data included satellite-derived SST imagery, tuna catch records from PPN Palabuhanratu, and the Dipole Mode Index (DMI) as an indicator of IOD variability. Thermal fronts were detected using the Single Image Edge Detection (SIED) algorithm with a 0.5°C gradient threshold. Results indicated that thermal fronts occurred most frequently during transitional and dry seasons, with peak intensity from October to December. Pearson correlation analysis revealed a negative relationship between SST and tuna catch (r = –0.340; CI = –0.547 to –0.094) and between IOD and SST (r = –0.549; CI = –0.705 to –0.344), suggesting that warmer waters and positive IOD phases reduce tuna catch volume. In contrast, thermal front intensity showed no significant correlation with tuna catch (r = 0.104), IOD (r = 0.083), or SST (r = –0.177). These findings suggest that while SST and IOD exert measurable influences on tuna catch, thermal fronts may not serve as reliable indicators for the yellowfin tuna fishing in the Palabuhanratu region.