How Does Salinity Influence Habitat Selection and Growth in Juvenile American Eels?

Despite the collapse in abundance of the American eel (Anguilla rostrata) in the upper St. Lawrence River, little remains known about the influence of environmental cues on habitat selection by glass eels (juveniles) and how this distribution affects growth. Glass eel’s salinity preference and locomotor activity were assessed in 4 rivers across eastern Canada for 2 sampling time periods in 2011 and 2012. Glass eels were categorized according to their salinity preference and the growth rate of each group was subsequently monitored in controlled fresh (FW) and brackish (BW) environments for 7 months. Most glass eels (78-89 %) did not show any preference toward either FW or salt water (SW) suggesting that a majority of glass eels may remain in brackish water environments in the wild. Neither the salinity preference showed by glass eels in previous experiments nor the rearing salinity influenced growth during the course of the experiments. However, glass eels from the Atlantic coast reached a significantly higher mass than those from the St. Lawrence Estuary, supporting the hypothesis of genetic differences between glass eels of different locations. Our results provide important ecological knowledge for the sustained exploitation and conservation of this endangered species.