PCBs and the energy cost of migration in the European eel (Anguilla anguilla L.).

The effect of polychlorinated biphenyls (PCBs) on the energy consumption of fasting silver European eel (Anguilla anguilla L.) was studied over a 27-day period during which the animals were at rest or were swimming 800 km in Blazka swim tunnels. Three-year-old female hatchery eels (silver stage) between 73 and 80 cm long weighing around 1 kg were dosed intraperitoneally with PCBs at a nominal dosage of 10x the consumption standard as a mixture representative for planar (7 microg PCB126/kg eel), non-planar (5 mg PCB153/kg eel) and metabolizable PCBs (50 microg PCB77/kg eel) found in wild eel, or only with the vehicle (corn oil, 10 ml/kg eel). Four major observations were made: (1) PCB-exposed animals lose less weight compared to their unexposed controls; (2) PCB-concentrations on a lipid basis are 2.8-14 times higher in swimming compared to resting animals; (3) the standard metabolic rate is significantly lower in the PCB-exposed animals than in unexposed controls. In addition, PCB-exposure significantly reduces oxygen consumption during swimming, and starting at 400 km (18 days) this effect increases with time; (4) the relative spleen and liver weight significantly increased in the PCB-swim animals but not in the PCB-rest animals. The swimming animals lost about 75% more weight compared to resting animals and had about 50% lower plasma fat content. Hematocrit, haemoglobin, plasma pH, ion levels (sodium and potassium), and plasma lactate were not affected by PCB-exposure or swimming. Apparently, the current levels of PCBs and other dioxin-like compounds may seriously impair the reproduction of the European eel.