Do feeding habits influence anthropogenic particle consumption in demersal fish in a tropical estuary? A study from the northern part of the Tropical Eastern Pacific

Felipe Amezcua^1*Carlos R Green-Ruiz¹Roberto Cruz-García¹José R Rivera- Hernández¹Victor Muro-Torres²

• ¹National Autonomous University of Mexico, México City, Mexico
• ²Centro de Investigación Biológica del Noroeste (CIBNOR), La Paz, Baja California Sur, Mexico

The presence of anthropogenic particles (AP), defined as materials that have undergone human modification, in an estuarine system, and their consumption by demersal fishes, were assessed in the northern part of the Tropical Eastern Pacific. The aim was to investigate how the type and quantity of microplastics ingested by demersal fish of different trophic levels, feeding habits, and feeding guilds vary, and if these relate to the APs found in water. Water and fish samples were collected from a network of stations through the estuarine system of Huizache-Caimanero, and the presence and characteristics of microplastics were analyzed. A total of 1,162 AP particles were identified in the water samples, the majority fragments. A total of 133 stomach contents from six fish species of different trophic levels and feeding habits were analyzed. Trophic guilds included planktivores, carnivores, and omnivores, and feeding guilds included zoobenthivores, piscivores, planktivores, and detritivores. The results showed a high frequency of microplastic ingestion in fish, with fibers being the most prevalent form. The most common polymers identified with the Fourier Transform Infrared (FTIR) spectroscopy, both in water and in the fish, were cotton and polyethylene terephthalate (PET). In water, alkyd resins were also important, and cellulose fibers and fragments of diallyl phthalate resin were found in much less abundance. For fish, nylon was also an abundant polymer, whilst polyethylene and acrylic were the least abundant. All these polymers align with the activities conducted in the study area. Our findings suggest that the position in the water column influences microplastic ingestion, rather than trophic position or feeding habits. This study provides valuable insights into the impact of AP contamination on coastal ecosystems and highlights the need for effective management strategies to mitigate its effects.