Analysis of Population Dynamics and Stock Condition of Skipjack (Katsuwonus Pelamis) in Purse Seine Gear Landed at PPI Lonrae, Bone Regency, South Sulawesi

Skipjack tuna (Katsuwonus pelamis) fishing is one of the most prominent capture fisheries activities in the Bone Bay waters. The primary fishing gear used is purse seine, often operated in association with fish aggregating devices (FADs). Skipjack caught in FAD areas tend to be smaller in size and subject to overfishing, making it difficult for Indonesia to significantly increase production through capture fisheries. Therefore, understanding the population dynamics and stock status of the skipjack caught by purse seine is essential. Catching individuals below optimal size can lead to a decline in population abundance and long-term yield. This study focused on assessing the population dynamics and stock condition of the skipjack in Bone Bay waters caught by purse seine gear with FADs. Research was conducted from February to June 2025, with a total of 1,024 skipjack samples collected. A stratified random sampling method was applied, and fish lengths were measured and classified into small, medium, and large size groups. Data were processed using the FAO–ICLARM Fish Stock Assessment Tools II (FISAT II) software to determine length–frequency structure, age composition, growth, mortality, exploitation rate, yield per recruitment, and stock condition. Results indicated that the skipjack population in Bone Bay waters, as caught by purse seine, comprised two age groups. The estimated asymptotic length (L∞) was 67 cm, with a growth rate (K) of 0.42 year⁻¹. Mortality parameters included total mortality (Z) 2.54 year⁻¹, natural mortality (M) 0.84 year⁻¹, and fishing mortality (F) 1.71 year⁻¹. The exploitation rate (E) was 0.67 year⁻¹, while the relative yield per recruitment (Y'/R) was 0.0307 g/recruitment. Stock assessment results showed that the skipjack stock in Bone Bay waters, under purse seine fishing pressure, had a feasibility percentage of 56%, placing it in the depressed or depleted stock category.