Invasive Species Compendium

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Abstract

Microplastics ingestion by the exotic fish Gambusia holbrooki in two Mediterranean coastal lagoons.

Abstract

Gambusia holbrooki is a small Poecilid fish, of North American origin that was introduced in the early 20th century in wetlands of the Iberian Peninsula for the biological control of mosquitoes. Currently it has populations in many wetlands and is considered one of the main invasive species on the peninsula. This fish feeds mainly on invertebrates, but they are also susceptible to ingesting and accumulating microplastic residues that are similar in size to some of their usual prey. In the present study, we analyzed the contents of the gastrointestinal tract of adult individuals of this species from two restored coastal lagoons, in order to characterize the ingestion of microplastics. The microplastic remains found were classified by size, in different categories (fibers and fragments) and by color. 156 specimens of Gambusia holbrooki were analyzed: 92 females (59%) and 64 males (41%). Females had a greater weight (0.43 ± 0.31g) and length (3.42 ± 0.63 cm) than males (0.11 ± 0.03 g and 2.60 ± 0.26 cm). 44% of the fish presented some microplastic residue (fibers or fragments) in their gastrointestinal contents. Most of the microplastics (48%) ranged between 100 and 400 µm. Blue fibers were the most common (more than 60%), while brown fragments were the most abundant (36%). Regarding the average number of microplastics per individual found in the gastrointestinal content, it was slightly higher in males than in females, in spring samples than in summer ones, and in lagoon G02 compared to L04, although only significant differences were found between the lagoons. When analyzing the number of ingested microplastics as a function of the weight of the G. holbrooki specimens, a slight trend showed that individuals with lower weights presented a greater amount of microplastics. In this sense, the presence of microplastics in the gastrointestinal contents of fish can be an indicator of the increase in plastic residues in Mediterranean coastal ecosystems, with the potential to alter the trophic dynamics of aquatic organisms.