Microplastic ingestion by perch (Perca fluviatilis Linnaeus 1758) from four Italian lakes

, Galafassi Silvia, Sighicelli Maria, Cau Alessandro, Gillibert Raymond, Temperini Maria Eleonora, Ortolani Michele, Bettinetti Roberta, Pietrelli Loris, Pusceddu Antonio, Zaupa Silvia, Volta Pietro.

Research on microplastic contamination has been mostly focused on marine environments and only recently attention has been paid also to freshwater environments. Among aquatic organisms, fish have received higher attention compared to other taxa in surveys for MPs detection. However, although publications on this topic are rapidly increasing, there is a high dispersion of data and, rarely, the same species is evaluated on a large number of different environments, allowing an analysis that can lay the foundations for its possible use as an indicator species for microplastic contamination of the food webs. In this study, the presence of microplastics in the digestive system of one of the most widespread and commercially exploited freshwater fish, the perch (Perca fluviatilis Linnaeus 1758), was investigated in four of the largest Italian South Alpine lakes: Como, Garda, Orta, and Maggiore. Microplastics occurred in 86% of the analysed specimens, with average concentrations ranging from 1.24 ± 1.04 ind-1 in L. Como to 5.59 ± 2.61 ind-1 in L. Garda. The isolated particles were mainly fragments, except in L. Como where films were more abundant. Most common polymers were polyethylene, polyethylene terephthalate, polyamide, and polycarbonate, although a high degree of degradation was found in 43% of synthetic particles, not allowing their recognition up to a specific polymer. Despite the high level of ingestion, MPs presence seems to do not affect fish body condition, evaluated though the hepatosomatic index and Fulton' body condition factor. Instead, an inverse linear relationship occurred between the number of ingested particles and fullness index, meaning that an empty stomach had a higher probability to contain microplastics. Presented data do not support the existence of a relation between probability of MPs ingestion and length or sex, as found for other fish species of either marine and freshwater environments.

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