Journal of Fisheries Science and Technology

Journal of Fisheries Science and Technology

Microplastic Abundance in the Rearing Water of Rainbow Trout within a Recirculating Aquaculture System (RAS)

Authors
Sina Vahdatirad 1
Ali mirghaed 2
Hosseinali Ebrahimzadeh Mousavi 2
Seyed Saeed Mirzargar 2
Mohammad Gholizadeh 3
1 Kish International Campus, University of Tehran
2 Department of Aquatic Animal Health, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran
3 Faculty of Agriculture and Natural Resources, Gonbad Kavos University, Gonbad Kavos,Iran
10.48311/jfst.2025.23898
Abstract
Microplastics are pervasive in aquatic ecosystems, and aquaculture products are susceptible to contamination from both external and internal sources. However, the presence and characteristics of microplastics in Iran’s freshwater aquaculture systems have not yet been investigated. This study aims to fill this knowledge gap by quantifying and characterizing microplastics in freshwater RAS facilities across two Iranian regions—Mazandaran and Golestan provinces. In autumn 2024 (Fall 1403 in the Iranian calendar), three liters of water were sampled from each station (inlet water, pre-tank filter, post-tank filter, and outlet water) in the RAS units located in both provinces. Microplastics were extracted from these samples and analyzed for abundance, shape, size, and polymer composition. Polymer types were identified using Fourier-transform infrared spectroscopy (FTIR). A total of 125 plastic particles were identified, with the highest mean concentration observed in Mazandaran Province (24 ± 2.02 particles per liter) and in the outlet water (29 particles per liter). Fiber-shaped microplastics dominated all samples (over 90%), while fragment types were the least common. Size class analysis showed that the 300–1000 µm group had the highest abundance, whereas the 3000–5000 µm group had the lowest. Black particles were most prevalent, and transparent and red particles were the rarest. The dominant polymer types were polyethylene (PE) and polyethylene terephthalate (PET). Evaluating how microplastics ingress into RAS facilities—whether through plastic component degradation—and exploring non-plastic alternatives for these components (such as natural biofilters), as well as removal techniques, is critical. These measures are essential to minimize contaminant presence in RAS.
Keywords
microplastics
Water
recirculating aquaculture systems
Polymer

Subjects

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