This study aimed to assess diet characteristics and ingestion of microplastics (MPs) by short mackerel (Rastrelliger brachysoma) based on fish size, water, depth, and season. Samples of fish were collected monthly from three depth contours during February 2019 and February 2020 by mackerel gill nets in the mouth area of Pattani Bay, Thailand. Plankton samples in the natural environment were simultaneously collected with fish sampling. Altogether, 541 individuals were used for stomach content analysis. The fish fullness index (FI) was influenced by season (p < 0.001), while the average number of food types (AF) was affected by fish size (p < 0.001) and season (p = 0.003). This fish is a specific planktonic feeder with a slightly low trophic level (2.39) and diet breadth (0.27). Diatoms (46.80%), calanoid copepods (15.85%), and dinoflagellates (13.95%) were the main food types found in the stomachs. While in the natural habitat, MPs contributed 7.04% of plankton samples, in this study, R. brachysoma stomach analysis found MPs contributed 0.35%. The ingestion of MPs was not affected by fish size, water depth or season (p > 0.05). The colors of MPs found were mostly blue, followed by green, red, and fragment. Based on diet composition and the prey selectivity index (-0.9), it is thus concluded that MPs are accidentally ingested by this species.

本研究旨在根据鱼的大小、水、深度和季节来评估短鲭鱼 ( Rastrelliger brachysoma ) 的饮食特征和微塑料 (MPs) 摄入量。在 2019 年 2 月和 2020 年 2 月期间，通过鲭鱼刺网在泰国北大年湾口区每月从三个深度等高线收集鱼样本。自然环境中的浮游生物样本与鱼类样本同时采集。总共有 541 人被用于胃内容物分析。鱼的饱满度指数（FI）受季节（p  < 0.001）影响，而平均食物类型数（AF）受鱼大小（p  < 0.001）和季节（p = 0.003)。这种鱼是一种特殊的浮游饲养者，营养水平（2.39）和饮食宽度（0.27）略低。硅藻 (46.80%)、calanoid 桡足类 (15.85%) 和甲藻 (13.95%) 是在胃中发现的主要食物类型。虽然在自然栖息地，议员贡献了 7.04% 的浮游生物样本，但在这项研究中，R. brachysoma胃分析发现议员贡献了 0.35%。MPs 的摄入量不受鱼的大小、水深或季节的影响（p  > 0.05）。发现的 MP 的颜色以蓝色居多，其次是绿色、红色和碎片。基于饮食组成和猎物选择性指数（-0.9），因此得出结论，MPs 被该物种意外摄入。