Plastic Pollution and Microplastics as Emerging Threats to Aquaculture: A Narrative Review

Aquaculture is increasingly critical for meeting global protein needs, with fish consumption having doubled since the 1960s. However, alongside its rapid expansion, the industry faces the emerging challenge of microplastic (MP) contamination. Microplastics, derived from degraded plastic debris, aquaculture infrastructure, and contaminated feeds, are now widely detected in pond water, sediments, and farmed fish tissues. This narrative review critically examined evidence on the impacts of MPs in aquaculture, with a focus on fish health and disease susceptibility. Findings suggest that MPs disrupt immune responses, inducing oxidative stress and inflammatory signaling while impairing lymphoid function. MPs also alter the gut microbiome, promoting dysbiosis, reduced feed efficiency, and heightened mucosal inflammation. Moreover, MPs act as vectors for pathogens such as Vibrio sp., Aeromonas sp., and Tenacibaculum sp., creating a “plastisphere” that shelters microbes, concentrates toxins, and facilitates disease transmission. These biological and ecological effects collectively raise concerns for aquaculture sustainability, fish welfare, and food safety. While uncertainties remain regarding dose–response relationships under farm conditions, the convergence of evidence highlights MPs as an underappreciated threat to global fish health. Mitigation strategies will require integrated approaches addressing plastic waste management, feed safety, and aquaculture system design.