Sexually Maturing American and European Silver Eels: Is Reproductive Capacity of Declining Eels Disrupted By Contaminants?

Several reasons may account for the decline of American (Anguilla rostrata) and European (Anguilla anguilla) eel populations. This study aims at developing a better understanding of eel reproductive biology, and to investigate the effects of contaminants on their reproductive capacity. Eels bioaccumulate contaminants during their long continental growth phase, then once they initiate their reproductive migration, fasting silver eels will exclusively rely on their energy stores and constituents for swimming and gonad development. Sexually maturing eels may therefore become particularly vulnerable to contaminant effects. We have undertaken artificial maturation of female downstream migrants from various locations in Quebec and France, and measured ovarian development together with neuro-endocrine parameters, body energy reserves, and contaminant levels. In this presentation, we examine and compare for both eel species the relative expression of genes encoding for cerebral releasing hormones (GnRH1, GnRH2), pituitary gonadotropins (LHβ, FSHβ), ERα estradiol receptor and hepatic vitellogenin, as measured by quantitative PCR. We will discuss the role of the brain-pituitary-gonadal-hepatic axis in eel ovarian development, as well as the possible influence of contaminants on these endpoints.