Hormonal Regulation of Upstream Migration in American Glass Eels

In recent years, freshwater, estuarine, and marine ecotypes have been described in different eel species. The aim of this study was to better understand the physiological regulation of migration at the glass eel stage in American eel, Anguilla rostrata. We hypothesized that the hormonal status would differ between glass eels exhibiting different ecotypes. Glass eels were captured when entering river estuaries in Nova Scotia (Mersey River) and Québec (Rivière Saint-Jean, Grande Rivière Blanche). They were transferred to Maurice-Lamontagne Institute (Fisheries and Oceans Canada), where the salinity preference was estimated for groups originating from the different rivers. Glass eels exhibiting freshwater preference, saltwater preference, or brackish water preference were measured, weighed, and their stage of pigmentation quantified; they were then preserved in RNAlater for genomic studies. We compared the expression of genes coding for cortisol, prolactin, growth hormone, and thyroid hormones well as for their respective receptors. The results will be discussed in relation to the zone of capture and salinity preference.