Plastic ingestion by marine fish in the wild

Marine plastic pollution has become a prominent environmental issue in the recent years. Plastic ingestion is of special concern, as its magnitude and consequences for marine organisms and potentially humans are still largely unknown. We reviewed 93 papers on plastic ingestion by wild marine fish published since 1972. Plastic ingestion was detected in 323 (65%) of 494 examined fish species, and in 262 (67%) of 391 examined commercial fish species. These proportions are likely greater, as a detailed analysis of the sampling effort and analytical methods used in the reviewed studies suggests an underestimation of plastic ingestion in some assessments. A significant positive relationship (R = + 0.845, p = 0.004) was found between the sample size up to N = 10 and the detection of plastic ingestion. We also found significant differences in detection and frequency of occurrence (FO, %) of plastic ingestion among the three main types of analytical methods: naked-eye, microscopic analysis and chemical digestion. The chemical digestion method, which is also the most robust laboratory method, had the greatest detection (86%) and the highest FO (37.6 ± 0.6%). To avoid the underestimation of plastic ingestion in future work, we provided recommendations for sample sizes and laboratory analysis.