Possible loss of polychlorinated biphenyls from migrating European silver eels: a 3 month simulation experiment

A 3 month experiment was set up to simulate the polychlorinated biphenyl (PCB) congener behavior in lipids during migration of silver eels, Anguilla anguilla, from river to sea. The thesis is that there should be loss of PCB contamination, to establish a new chemical equilibrium between the lipid and water compartments, where metabolism is the vehicle. Male and female eels collected in the River Rhine were placed separately, and in duplicate, in aquaria with running seawater of 5°C under starvation conditions for 91 days. Eels were sampled at regular intervals for the determination of eel-conditional parameters and PCB congener analysis. Also, water and particulate matter were analyzed for PCB congeners. Wet weight, lipid content, condition of organs such as heart, liver and spleen did not change throughout the experiment, at least not within the accuracy of the investigations and there was no indication of sexual maturation. This agrees with literature information and, for loss of weight, with theoretical calculation based on energy budget. The PCB congener chromatograms of eels showed little difference in time, and did not demonstrate any loss from the lipid compartment due to exposure to less contaminated seawater. The eel chromatograms showed the typical congener distribution with higher values at 2/3 of the chromatogram, also found earlier for mussels, and relative to that of water. The process of attaining a new partitioning equilibrium between the lipid compartment in gill-breathing aquatic organisms and that of water was not found. Neither were there changes in the PCB congener chromatograms due to selective metabolic activities. Using PCB congener No. 138 as reference, a congener that remained rather constant in the lipids of eels, only two congeners, Nos. 105 and 118, showed a significant increase with respect to No. 138. Starvation possibly retards metabolic activity and thus also inhibits loss of PCB congeners to the seawater compartment. Therefore, PCBs may remain as toxic contaminants in the lipids of fasting and migrating eels, which potentially may have noxious effects during migration and maturation. However, a noxious effect was not found during this experiment.