Satellite-based GAM-MaxEnt modeling of Indian mackerel habitat hotspots in the Makassar Strait, Indonesia

Abstract

Understanding how dynamic oceanographic processes structure pelagic habitats remains a central challenge in equatorial fisheries oceanography, shaped by strong frontal systems and seasonal upwelling. This study synthesizes multi-year fishery observations and satellite-derived environmental data (2015–2021) to quantify habitat suitability of Indian mackerel in the Makassar Strait, Indonesia. Seven remotely sensed and oceanographic variables sea surface salinity (SSS), chlorophyll-a (CHL), sea surface height (SSH), mixed layer depth (MLD), net primary productivity (NPP), sea surface temperature (SST), and sea surface currents (SSC) were integrated into a Pelagic Habitat Index (PHI) using an ensemble framework combining Generalized Additive Models and MaxEnt modeling. The integrated approach demonstrated effective broad-scale predictive performance and spatial transferability. Independent validation using 2022 observations showed a relatively high predictive skill (R 2 ≈ 0.69), while spatially blocked cross-validation indicated limited fine-scale geographic transferability. Predicted habitat hotspots closely matched observed catch distributions, and hotspot-overlap analyses indicated statistically significant agreement beyond random expectation, demonstrating that the model captures ecologically meaningful habitat productivity relationships. Spatially, core habitats were concentrated in the southwestern Makassar Strait and persisted for 6–10 months annually, closely associated with SSS and CHL fronts intensified during the southeast monsoon. These frontal systems, reinforced by seasonal upwelling and enhanced productivity, coincided with peak catches in October, highlighting their role as key feeding and spawning environments. By linking satellite-observed ocean dynamics with fisheries productivity, this study provides a spatially explicit framework for forecasting broad-scale pelagic habitat variability, supporting ecosystem-based fisheries management and adaptive exploitation of tropical pelagic systems under changing oceanographic and fishery conditions.

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