Characteristics and differences of microplastics ingestion for farmed fish with different water depths, feeding habits and diets

Microplastics have become a potential hazard to the quality and safety of aquatic products although there are few reports on microplastics distribution related to water depth, feeding habits and diets in aquaculture ponds. In this study, five aquaculture fish species (Ctenopharyngodon idella, Hypophthalmichthys molitrix, Cirrhinus molitorella, Oreochromis niloticus and Pelteobagrus fulvidraco) were selected and their accumulation of microplastics was measured and classified. We found that the water depth, feeding habits and diets led to large differences in microplastics accumulation. The bottom-dwelling omnivorous fish had the largest ingestion of microplastics and ranked as P. fulvidraco > O. niloticus > C. molitorella,the herbivore C. idella in the middle benthic layer and the upper-layer filter-feeder H. molitrix had the lowest ingestion. The detection frequency in the gastro-intestinal tracts for C. idella, H. molitrix, C. molitorella, O. niloticus, and P. fulvidraco were 93.33%, 91.67%, 87.50%, 92.86%, and 90.91%, and detection frequencies for gills were 86.67%, 100%, 87.5%, 100%, and 81.82%, respectively. Fibers presented the dominant shape (91.92%) and blue was the primary particle color in the majority of the samples (77.39%) and 0.5-2 mm particles dominated. The plastics were composed of olefins, acrylic, rayon, polyester, polyethylene and polypropylene. Our study first reported the relationship between MPs accumulation and water depth, feeding habits and diets in aquaculture ponds, which also has a certain correlation with the fish size.

Automated summary

Microplastics accumulation in aquaculture ponds is influenced by water depth, feeding habits, and diets. Bottom-dwelling omnivorous fish have the highest ingestion, while herbivorous fish and filter-feeders have lower ingestion.