<![CDATA[Graphical Abstract Highlight Research Microplastics were detected in the gills and stomach of S. vermiculatus. Microplastic abundance was higher in the gills than in the stomach. Fiber were the most dominant shaped of microplastic in both organs. FTIR analysis confirmed the presence of PE, PES, PP, and HDPE in a selected subset of particles. Abstract Surveys of organ-specific particles in fish provide baseline evidence, but visual identification and selective polymer confirmation require distinct interpretations. This cross-sectional observational study compared suspected microplastic-like particles in paired gill and stomach samples from Siganus vermiculatus landed at Palopo Fish Landing Port, Indonesia. Fifteen fish were selected by convenience sampling from a single catch on August 7, 2025. Following 10% KOH digestion, particles were examined by stereomicroscopy; 20 selected particles underwent Fourier-transform infrared (FTIR) spectroscopy with a spectral similarity threshold of 70%. Visually suspected particles occurred in all 15 fish, totaling 107: 64 in gills and 43 in stomachs. Mean counts were 4.27 ± 1.44 and 2.87 ± 0.99 particles per fish, respectively, yielding a paired difference of 1.40 particles (95% confidence interval, 0.42–2.38; t(14) = 3.073; p = 0.0083). Fibers predominated in both organs, and the 1–5 mm category accounted for most observed particles. Seven of 20 FTIR spectra met the matching criterion, identifying polyethylene (including high-density polyethylene), polyester, and polypropylene in the analyzed subset. Thus, gills contained more visually suspected particles than stomachs within this single-catch sample, without establishing exposure pathways or environmental sources. Plastic-bag storage, absent procedural blanks, selective chemical confirmation, and limited sampling constrain polymer attribution and wider inference. Future studies should incorporate contamination controls, broader FTIR verification, and repeated sampling to assess whether this organ-specific pattern persists across catches and locations. Exploratory correlations with fish length and body weight were weak and negative (r = −0.052 and −0.128, respectively), with substantial uncertainty from limited sampling.]]>
