Microplastics in gastrointestinal tracts of Trachurus trachurus and Scomber colias from the Portuguese Coastal waters

Plastic and microplastics are ubiquitous in the marine environment, their presence and possible ingestion can lead to harmful consequences in the marine environment and biota. To provide a quantification of microplastics ingested by commercial fish from the Portuguese Coastal waters and public awareness of the potential harm to human health, a total of 164 samples of Trachurus trachurus and Scomber colias were collected from Figueira da Foz and Sesimbra fishing ports. After dissection and evaluation, 67% of the individuals were found to have ingested microplastics. A total of 399 microplastics were registered, with an average (mean  SD) of 3.63 ± 3.16 microplastics per contaminated fish. Fibres and fragments were the type of MP found in fish, fibres were recurrently found among individuals, 79% comparing to 21% of fragments. Fish collected from Figueira da Foz fishing port, comprise 62% of the total MPs detected, and, S. colias, the Atlantic mackerel ingested 54% of the total microplastics. Kruskal Wallis H test were performed to identify significant statistical differences between sampled groups and Spearman correlation to link any possible relationship between biometric parameters and number of microplastics ingested per fish. Intra-species comparisons identified significant differences in the number of fibres ingested and in the gastrointestinal tract weights, while inter-species comparisons revealed differences in the amounts of fibres and fragments ingested among individuals. Slight Spearman correlations were registered between the biometric parameters and the number of fibres and fragments ingested.