Assessing the seasonal uptake of micro-litter by round sardinella (Sardinella aurita Valenciennes, 1847) and its potential health impact in the NW Mediterranean Sea

This study quantifies and characterises the seasonal ingestion of anthropogenic items (AIs), including microplastics, by round sardinella ( Sardinella aurita ) from the coast off Barcelona (NW Mediterranean Sea), and assesses their potential impact on fish health through body condition indices and histological assessment. For this purpose, 100 specimens were seasonally captured aboard commercial purse seiner fishing vessels between 2022 and 2023. Present findings indicate that cellulosic fibres were predominant throughout the year (representing 73.56% of all AIs ingested). Fish ingested a mean of 2.27 (SD = 2.13) items/individual, with winter 2023 being the season with the highest abundance of AIs ingested and summer of the same year the lowest (GLM, p< 0.05). Seasonal variations in AIs ingestion were consistent with environmental ( i.e. rainfall rates, thermocline stratification) and biological ( i.e. feeding behaviour, reproduction) factors. Thus, higher AIs ingestion in winter coincided with increased feeding intensity and filter-feeding behaviour, whereas lower AIs ingestion in summer of 2023 was associated with reduced feeding activity, particulate-feeding behaviour and lower rainfall and riverine inputs. None of the histopathological alterations observed could be attributed to AIs exposure, even during the season with the highest ingestion rates. Studies with a seasonal approach, as the present case, are crucial for identifying periods of high AIs exposure and for accurately assessing the potential risks to fish condition, providing valuable insights into the temporal dynamics of AIs ingestion in marine species.