Organic and Metallic Pollutants Reduce the Diversity of Life-History Traits in European Eel: The End of an Evolutionary Advantage?

During EELIAD project, we examined effects of contamination by metals, POPs (including PCB) and introduced parasites on life history traits of 450 silver eels sampled across Europe. Our results showed a positive relationship between age and latitude, while size & weight at silvering were correlated to catchment characteristics. Growth rate was linked to catchment productivity, habitat preferences and migratory patterns experienced during the growth stage. Fat content was highly variable between individuals but no geographical pattern was depicted. This suggests that eels adjust their life history to an incredible range of environmental conditions to ensure breeding success.  This confers an undeniable evolutionary advantage to European eels that were able to survive to a number of major environmental crisis since at least 30 MY.  Contamination is likely to trick this advantage: metallic and parasite loads were negatively correlated to age and size at silvering. PCBs were present in every single eel at high concentrations in some catchments, and a negative low but significant correlation was found with GSI and fat content. These results strongly suggest that the winning breeding strategy of eels has recently been impacted, fattest, largest and oldest, ie the most potentially successful eels, been more impacted than others…