Population genetic structure and biochemical markers in a cyprinid (Leuciscus cephalus) exposed in situ to pollutants

The aim of this work was to assess the responses at the individual and at the population level of feral fish exposed to pollutants. Both genetic markers (4 allozyme-linked loci) and biochemical markers (DNA strand breaks in erythrocyte nuclei and enzymatic EROD activity in fish liver) were measured in fish caught in a low polluted area (River Drôme) and two heavily polluted stations (River Turdine and River Rhône). EROD activity was significantly induced in polluted stations compared to the reference one. In contrast, only fish from the River Rhône exhibited a significantly higher DNA damage level compared to other sites. In comparison to the reference station, two trends were observed in fish populations from the polluted areas: i) a decrease in genetic heterozygosity (H) at the Turdine station (mainly expressed as the presence of the most common alleles),ii) maintenance of H value and presence of a specific allele (PGM allozyme) at the Rhône station. At the individual level it has to be noted that DNA integrity decreases when H increases. Both further multivariate and chemical analysis are under investigation to explore the potential relationships between genotypes and the measured biomarkers. / Afin de comparer des réponses biologiques chez les poissons au niveau individuel et au niveau populationel, nous avons prélevé des chevaines dans un site témoin (Drôme) et deux sites contaminés (Turdine et Rhône). Les résultats montrent des tendances complémentaires sur les différents marqueurs mesurés : EROD, génotoxicité et variabilité génétique. Ce type de mesure multi marqueurs est prometteuse et sera poursuivie dans l'avenir.