Abstract

Despite being identified as key pollution hot spots, debris dynamics in fishery harbors (FH) are poorly characterized. This study provides a comprehensive evaluation of macroplastic accumulation patterns in five FH of the Western Province of Sri Lanka through one complete annual cycle. Plastic was the major pollutant type (~85%), with single-use plastics (60.92%), considerably exceeding fishery-related plastic debris (9.67%), even though the study was conducted in fishery-specific settings. Spatial variation was substantial across FH with infrastructure design proving to be the key controlling factor in debris retention rather than environmental factors such as rainfall and tide level. Breakwater-enclosed FH designs recorded considerably higher dynamics compared to open designs and localized zones of high accumulation of the plastic debris were recognized in particular infrastructure geometries. Seasonal patterns were present at some FH, with peak accumulation during the second inter-monsoon and northeast monsoon period, which was driven by intensity variation in the operations and not directly by environmental forcing. Debris originated mainly from local sources with negligible contribution of transboundary debris. The accumulation is governed by hierarchical controls, with infrastructure design as the primary, operation intensity as the secondary, and environmental setting as the tertiary determinant. These findings provide evidence that effective management requires infrastructure-based solutions and local waste management interventions, rather than strategies suggested for environmentally driven coastal systems. The infrastructure-based classification framework and evidence-based prioritization methodology are replicable tools to support policy development and an increase in the optimization of limited available resources for sustainable FH operations worldwide.