Sea Surface-Visible Marine Aquaculture in Tunisia

Mapping spatio-temporal distribution through satellite imagery and geospatial analysis (2004-2026)

Abstract

Offshore aquaculture is increasingly recognized as a strategic component of sustainable food systems and Blue Economy development; however, its long-term spatial dynamics remain poorly documented in many regions, particularly in North Africa. This study reconstructs the evolution of marine aquaculture concessions in Tunisia between 2004 and 2026 by integrating administrative concession records with multi-temporal satellite imagery.

A geospatial database was developed for 70 authorized sites, complemented by systematic interpretation of high-resolution historical imagery and Sentinel-2 data to map cage occupancy, infrastructure evolution, and spatial configuration. The results reveal a strong path-dependent development pattern, where early site allocation decisions largely determined long-term spatial persistence.

More than half of concessions remained active, while a significant proportion failed to reach sustained production, highlighting heterogeneity in site performance. Satellite-based reconstruction shows a marked expansion of finfish farming, alongside a progressive shift toward larger cages, standardized infrastructure, and more complex multi-line farm configurations. Atlantic bluefin tuna fattening remained spatially restricted throughout the study period. A gradual offshore shift toward deeper waters was also observed.

Beyond methodological contributions, the resulting dataset provides a robust baseline for Marine Spatial Planning and Integrated Coastal Zone Management by distinguishing between authorized and effectively occupied sites (sites with visible aquaculture infrastructure), supporting evidence-based zoning and long-term coastal governance.