Impacts of Microplastics on the Early Life Stages of Fish: Sources, Mechanisms, Ecological Consequences, and Mitigation Strategies

Microplastics represent an emerging threat to aquatic environments and organisms, as they infiltrate water systems, are ingested by marine species, and cause physical harm, endocrine disruption, and bioaccumulation up the food chain, potentially impacting biodiversity and human health. Aquatic ecosystems face considerable harm from microplastic pollution because fish in the early developmental stages, including embryos, larvae, and juveniles, are more susceptible due to their immature physiological and detoxification systems. This review aims to comprehensively explore the impacts of microplastics on the early life stages of fish. Aquatic environments receive primary and secondary MPs from urban runoff and industrial waste, together with degraded plastics, which affect fish embryos and larvae via direct ingestion, surface adhesion, and trophic transmission pathways. The physical impact of MPs causes digestive tract blockages that reduce hatching success and create developmental problems in fish organs, but chemical toxicity develops from plasticizers, heavy metal leaching, and pollutant adsorption, which causes oxidative stress, endocrine disruption, and metabolic dysfunction. Survival rates decrease because exposure causes fish to perform poorly during swimming activities and make limited efforts to avoid predators. The small dimensions and high chemical reactivity of MPs increase their bioavailability, which promotes tissue penetration and leads to accumulation at different levels of the food chain. This comprehensive review emphasizes that we need to establish uniform detection protocols, long-term exposure research, and effective strategies to control MP pollution. The resolution of these difficulties remains essential for protecting fish populations, as well as for protecting biodiversity and minimizing seafood contamination risks to human health.