In 35 Years of Monitoring, Lipid Levels of Eels (Anguilla anguilla) Have Not Declined, Nor Can Negative Effects of PCBs on Eels be Demonstrated

In this presentation we show that shifts in eel sexe-ratio can have large effects on both the observed bioaccumulation of POPs and on the lipid content. Without accounting for eel ecology, bioaccumulation levels can be misinterpreted both environmentally (comparing pollution levels between locations and years) and in alleged eco-toxicological effects of PCBs.

In the long term monitoring programme of IMARES, 25 yellow eels with lengths between 30 and 40 cm are used for composite samples, in which PCBs, sum-TEQ,  OCPs and lipid content were analysed. In 2011, an additional 25 yellow eels of 30-40 cm length and 25 yellow eels of lengths above 40 cm were captured at two locations; these were analysed individually.  Sexe ratio between these locations were different.  Male eels contained more lipids than females at similar lengths, but at higher lengths females reached the same lipid contents (up to 30%). POP levels were positively correlated with lipid content in all eels. The observed decrease in lipid content in the composite sample over the years in some locations  could be correlated to decreasing numbers of males. Neither lipid contents in yellow or silver eel, nor the sex ratio were influenced by PCB or sum-TEQ levels.