Abstract
The commercial demand for small pelagic fish, such as Atlantic chub mackerel (Scomber colias), renders them susceptible to provenance fraud. Scomber colias specimens intestinal tract bacteriome from five distinct fishing areas along the Portuguese Atlantic coastline were analyzed by 4th-generation sequencing. Bacteria diversity indices and differential abundance revealed dissimilarities in operational taxonomic unit (OTU) abundance among specimens from distinct fishing sites. Random forest-based model yielded an 85% accuracy rate in attributing sample provenance based on intestinal tract bacteriome OTU relative abundance. Further refinement of microbial features using Indicator Species Analysis, Linear Discriminant Analysis Effect Size (LEfSe) and OTU Gini scores enabled the identification of 3-5 bacterial OTU location biomarkers per fishing site. The intestinal tract bacteriome revealed sequences linked to pathogenic bacteria, particularly in specimens from Center-North and Center-South fishing areas. While this doesn't imply active pathogens, it highlights potential public health concerns and complements efforts to improve seafood microbiological quality and traceability.