The Makassar Strait (MS) is characterized by water mass from the Pacific Ocean and is one of the ITF (Indonesia Throughflow) branches. It carries warm water masses from the Pacific Ocean to the Indian Ocean. This research aims to analyze the relationship between CPUE of Eastern Little Tuna (Euthynnus affinis) and oceanographic variables, likewise predict the fishing area using the Generalized Additive Model (GAM). The research method used is spatial and temporal analysis. The data was used from 2015 to 2020. The data processed were sea surface temperature, chlorophyll-a, salinity, currents, sea level as predictor variables, and Eastern Little Tuna production as a response. Eastern Little Tuna catch data were normalized into Catch per Unit Effort, while the oceanographic data were extracted using ArcGIS. Based on the results of the GAM model, it was found that the model with five variables is the most suitable predictive model, with 16.4% CDE. Salinity is the most influential parameter on the catch of Eastern Little Tuna with a significance value of <2.00 × 10⁻¹⁶ ***. The optimum value for SST is 30–31 °C, chlorophyll-a is 1–2 mg/m³, salinity is 29–30 ppt, current velocity is 0.3–0.5 m/s and sea level is between 0.6–0.7 m. Based on the GAM prediction results, a high CPUE value will be obtained in the southwest monsoon (March to May). Fishing activity carried out in the best season will implement the adoption of harvest control measures.

Sea level is a key oceanographic variable that exhibits both spatial and temporal variability and serves as an important indicator of global and regional ocean–climate variability, which can influence fishery productivity. Using satellite observation data, this study aimed to identify patterns and fluctuations in sea level trends and variability, and to examine their effects on the catch rates of Eastern Little Tuna (Euthynnus affinis) in the Makassar Strait over a ten-year period (2013–2022). Sea level time series were generated through averaging calculations and spatial mean mapping to characterize sea level distribution. Histogram analysis was applied to determine the frequency of catch per unit effort (CPUE) across different sea level ranges. The results showed that mean sea level in the Makassar Strait during the study period ranged from 0.48 to 0.78 m. Clear annual and seasonal sea level variability was observed, with higher values (0.65–0.70 m) during the northwest monsoon and lower values (0.50–0.60 m) during the southeast monsoon. Over the ten-year period, sea level increased by approximately 0.13 m. The highest CPUE of Eastern Little Tuna was associated with sea levels between 0.60 and 0.65 m. Histogram analysis further indicated that this sea level range corresponded to the maximum CPUE values. In contrast, higher sea levels ranging from 0.75 to 0.80 m were associated with the lowest CPUE, value of 30 kg/trip.

Ocean warming, driven by increasing sea surface temperatures, is a key factor altering the distribution of pelagic fish, notably the Eastern Little Tuna or ELT (Euthynnus affinis). This study examined satellite-derived SST data and ELT catches to determine the SST preferences of ELT and to predict their potential habitat in scenarios where SST increases by 1 and 2ºC. We analyzed all datasets from January 2015 to December 2020. The findings indicated that most ELT caught in an SST ranged from 30 to 31ºC during the first transitional season (TS 1/March-May). The wavelet analysis confirmed that SST has a strong interseasonal (6-8 months) signal along the observation period. Similarly, ELT catches also exhibited strong interseasonal signals, particularly from the middle of 2018 to the middle of 2019, and intra-seasonal patterns from early 2015 to the middle of 2019 (1 – 6 months). The monthly mean climatology of SST during 2015 – 2020 with the SST value of 30 - 31ºC designated as the preferred habitat of ELT is found every month, especially in January-April. The habitat preference for ELT seemed to be reduced under a scenario of increasing 1ºC and 2ºC. Furthermore, our results revealed that increasing SST due to ocean warming may shift the fishing season and shorten its length from six to three months. These insights enhance our comprehension of how ocean warming impacts ELT's potential habitat in the Makassar Strait, informing improved fisheries management and climate change mitigation.