Microplastics are plastic particles smaller than 5 mm in diameter. Due to their persistence and ease of dispersion, they represent a growing concern in aquaculture. These particles can be ingested by aquatic organisms and accumulate in tissues such as the gastrointestinal tract (GIT). This study investigated the occurrence of microplastics in Florida Red Tilapia reared in a Recirculating Aquaculture System (RAS) over a 90-day experimental period, under two conditions: a plastic-covered area and an uncovered area, each comprising juvenile and adult stages. Fish were sampled at the beginning and end of the production cycle. After biometry, the digestive tracts were removed and digested with 150 mL of hydrogen peroxide (H₂O₂) at 60°C for 48 hours. A control sample containing 25 mL of H₂O₂ was processed under the same conditions. The resulting material was filtered through glass fiber filters (Whatman GF/F) and analyzed under a stereomicroscope equipped with a camera and Image View software for particle identification, counting, measurement, and morphological classification.
The results revealed a significant difference in mean particle size between cultivation areas (one-way ANOVA; F = 10.11, p < 0.01), while no significant difference was found between maturation stages. In terms of particle number, the two-way ANOVA showed no significant effects of either cultivation area or maturation stage. Morphological analysis indicated that fragments were the most frequent particle type, with blue being the predominant color, followed by red and yellow.
The higher MPs size in the uncovered area may be related to a greater exposure to external sources of contamination, such as dust and debris carried by wind or rain, which can introduce larger particles. The cover may have acted as a physical barrier, limiting this entry. The presence of microplastics in the tilapia indicates ongoing contamination, possibly associated with the feed, water, and system materials, reinforcing the need for mitigation and monitoring strategies.