Marine Litter in some fish species off the coast of Peniche

• ¹ Faculdade de Ciências, Universidade de Lisboa, MARE, Portugal
• ² Faculdade de Ciências, Universidade de Lisboa, Centro de Química e Bioquímica and Centro de Química Estrutural, Portugal
• ³ Faculdade de Ciências, Universidade de Lisboa, Biologia Animal, Portugal

The seas and oceans around the world show increasing signs of environmental degradation, among which the presence of marine litter stands out. This study aimed to characterize the type of litter present in the gastrointestinal tract of 5 commercial fish species on the coast of Peniche, two pelagic fish species (Atlantic Horse Mackerel - Trachurus trachurus and Atlantic Chub Mackerel - Scomber colias) and three demersal fish (Poutine - Trisopterus luscus, species of the family Triglidae and Rajidae). The organic content present in the digestive tract of 150 fishes was digested by using a solution of 10% potassium hydroxide (KOH) to facilitate the extraction/isolation of debris. Fourier transform infrared spectroscopy (FTIR) was used to identify the type of polymers found in the gut contents. The results showed that the marine debris present in the samples were exclusively composed of microplastic. In total, 140 particles were found in 34.7% of the fishes analysed in the study, 86% of which were fragments of multiple plastics and the remaining were fibers from clothes and fishing instruments. The great majority of the particles found (40%) presented a white coloration. On average, the fishes that ingested debris presented 2.06 ± 1.51 (SD) of particles in their gut contents, with pelagic fish presenting a significantly higher amount of microplastics compared to the demersal ones. This trend may be attributed to differences between the type of feeding and life habits, which characterize pelagic and demersal species. Because microplastics have a positive buoyancy it is expected that this marine pollutant is more likely to affect pelagic organisms as they inhabit the water column in the ocean, as found in the present study. The species with the highest consumption of debris, exclusively composed of microplastic (66.7% of the individuals sampled), was the Atlantic horse mackerel. Among the type of polymers identified, it was concluded that polyurethane (PU) was the most common polymer found in the gut contents of the fish analysed in the present study.