Identifying local migration and habitat use of reproductive skipjack tuna (Katsuwonus pelamis) in the Bone Bay–Flores Sea, Indonesia

Abstract

Understanding the spatial behavior of reproductively mature skipjack tuna ( Katsuwonus pelamis ) is vital for sustainable fishery management in tropical marine ecosystems. This regional case study examined reproductive skipjack tuna habitat use in the Bone Bay–Flores Sea, Indonesia, integrating histological maturity assessment with satellite-derived sea surface temperatures (SST) and sea surface chlorophyll-a (SSC) from MODIS-Aqua to support management-relevant spatial guidance. Histological analysis of 200 samples identified reproductive stages to post-ovulatory follicles, confirming maturity at fork lengths ≥ 50 cm. Among the 45,225 catch records analyzed, only approximately 32% represented mature fish, while the remaining 68% were immature, indicating potential recruitment overfishing. Mature skipjack tuna were found in waters with SST between 29.2–30.6°C (mean ± SD: 30.05 ± 0.27°C) and SSC concentrations of 0.18–0.32 mg m –3 (mean ± SD: 0.22 ± 0.04 mg m –3 ). Spatial analysis using Pelagic Hotspot Index (PHI ≥ 0.75) and Center of Gravity (COG) methods identified persistent spawning zones across the years. These results underscore the ecological importance of specific oceanographic conditions and advocate for spatiotemporal management strategies. Recommendations include setting a minimum catch size of ≥ 50 cm, seasonal protection of spawning grounds, and the use of remote sensing for dynamic fishery monitoring. This approach offers a valuable model for ecosystem-based fishery management, particularly in data-limited tropical regions.

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