Anthropogenic particles in stomachs of anchovies (Engraulis encrasicolus) related to gill rakers morphology

Anthropogenic debris (AD) contaminate oceans and affect marine organisms in several ways. Plastic production is constantly increasing and it is estimated that 10% of this production end in the seas. As a consequence, plastic is considered as an emerging contaminant and ingestions by organisms are increasingly reported. Microdebris (< 5mm) are available for a high range of organisms, including planktivorous fish, such as the European anchovy (Engraulis encrasicolus). Planktivorous fish have a particular gill basket, with long and tight gill rakers, related to their diet. Upon these gill rakers, small structures called denticles are present. These gill rakers act as a net to trap organic particles and AD. The aim of our study was to correlate sizes of AD ingested with the mesh constituted by the gill rakers and associated structures. Fifteen stomach contents were analyzed by Raman spectroscopy and particles were measured. Five gill arches were observed with a scanning electron microscope. Cellulose fibers and microplastics were the most AD ingested. Comparing to other Clupeiformes (pilchard and Atlantic herring), anchovies have more denticles on each gill rakers (personal data). AD ingestion by fish is poorly studied and impacts of AD are not much understood. Clupeiformes play a major role in marine ecosystems and is the most consumed order by humans. As the branchial basket constitutes a food selective apparatus, more morphological studies dealing with AD ingestion on Clupeiformes are needed