A study compared the contamination of European eels between different sites in the Camargue.
The European eel is an emblematic species of estuaries and lagoon, and a surprising animal. As a larva, its very first journey covers several thousand kilometres, in order to reach the European continent, all the way from the Sargasso Sea. There, eels will grow for several years before travelling back across the ocean to reproduce. The eel is an amphihaline species, which means that it is able to live in both saltwater and freshwater. But this fascinating species is critically endangered, notably by the loss of wetlands and overfishing, and is also severely affected by contamination and parasitism.
A team of researchers assessed the quality of around sixty eels caught at three different sites within the Mediterranean lagoon complex of the Camargue. This assessment was carried out from an ecotoxicological (quantification of persistent organic pollutants – POPs – and trace elements – TEs) and epidemiological (infestation by the parasite Anguillicola crassus) point of view, whilst taking into account the individual characteristics of the eels (length, age, growth rate and sex).
Changes in contamination depending on the site
Their results, published in the journal Environmental Science and Pollution Research, show that the quality of eels generally decreases with age. The contamination of eels by POPs and TEs varies according to the site of capture. It is higher in a canal draining farmland and in the Grand Étang de Vaccarès than in a basin less exposed to agricultural inputs. According to Amélie Hoste, first author of the article as well as doctoral student at the M.I.O. of Aix-Marseille University and at the Tour du Valat: ‘The spatial variability revealed by this study suggests that reducing industrial and agricultural pollution leads to an improvement in the quality of the European eels present in these environments.’
Susceptibility to parasites A. crassus
The infestation rates of the nematode A. crassus also increased with the age of the eel, despite the fact that this parasite is known to survive poorly in brackish waters such as those of the Vaccarès lagoon. According to Delphine Nicolas, fish conservation biology researcher at the Tour du Valat: “It has been observed that, in some cases, POPs contamination can weaken the eel’s immune system, thus increasing their susceptibility to infectious diseases and parasites. For example, in the Vaccarès pond, eels that are contaminated by POPs might be more vulnerable to parasitism by the nematode A. crassus, despite their lower prevalence.’
The contamination of eels reflects that of their habitats
The same contaminants as those found in the sediments collected at the capture sites were detected in the eels. In addition, analyses of the eels revealed the presence of other contaminants not detected in the sediments, such as PCBs. Delphine Nicolas, researcher in fish conservation at the Tour du Valat, concludes: ‘It is difficult to determine the impact of all the contaminants on eel biology, especially as there may be “cocktail” effects. It is urgent to limit chemical inputs into aquatic environments, particularly those already clearly identified as dangerous.’
Hoste A., Lagarde R., Amilhat E., Bouchard C., Bustamante P., Covaci A., Faliex E., Migne E., Poma G., Tetrel C., Verbrugghe K., Vey Payre H., Nicolas D. 2025. Investigating the quality of European silver eels by quantifying contaminants and parasite infestation in a French Mediterranean lagoon complex. Environ Sci Pollut Res [Internet] [cited 2025 Jan 27]. doi: 10.1007/s11356-024-35815-0