Integrative Approach to Quantify and Characterize Risk of Micro‑ and Meso‑plastics in the Gastrointestinal Tracts of Fish from Lagos Commodore Channel.

This study aimed to delineate the physical (shape, size, and color) and chemical characteristics (polymer types) of micro- and mesoplastics in the gastrointestinal tracts (GIT) of fish species in the Lagos Commodore Channel, and to develop a conceptual methodology for investigating these pollutants. Ninety (90) fish individuals of three species, pelagic (Ethmalosa fimbriata) and demersal (Pseudotolithus elongatus and Pseudotolithus senegalensis), were captured fortnightly for three months (June and August 2025). The microplastic shapes in E. fimbriata, P. elongatus, and P. senegalensis were predominantly filaments (53.3-53.8%), followed by fragments (23.1%), fibres (7.7-15.4%), and other shapes, while mesoplastics comprised fibre (41.7%) and filaments (58.3%). A total of fifty (50) polymer types were identified in the GIT of three fish species. The abundance of polymer in the GIT of fish species was as follows: P. senegalensis (217) > P. elongatus (179) > E. fimbriata (124). The polymer-based particle contamination factors (ppCf) revealed low contamination levels. In contrast, polymer risk indices (pRi) varied from medium risks in E. fimbriata to considerable risk in P. elongatus and P. senegalensis. The Polymer Hazard Index (PHI) demonstrated a low pollution level in E. fimbriata, but demersal species P. elongatus and P. senegalensis exhibited low and high contamination levels, respectively. Demersal species showed a higher microplastic ingestion rate (76.15%) than pelagic species (23.85%), likely due to polymer density-related ingestion patterns. The significant species-specific contamination levels underscore the pressing need for targeted mitigation and continuous monitoring to protect ecosystem health and fisheries sustainability in this critically important coastal waterway. Highlights. • Fifty polymer types were identified in the gastrointestinal tracts of three fish species: E. fimbriata, P. elongatus, and P. senegalensis. • Polymer concentrations varied among species: P. senegalensis (217 particles/g) > P. elongatus (179 particles/g) > E. fimbriata (124 particles/g). • ppCf indicated low contamination, while pRi showed medium risk in E. fimbriata and considerable risk in P. elongatus and P. senegalensis. • PHI showed low contamination in pelagic E. fimbriata, and low to high contamination in demersal P. elongatus and P. senegalensis. • Demersal species ingested more microplastics (76.15%) than pelagic species (23.85%), linked to polymer density patterns.