Abnormally elevated VTG concentrations in flounder (Platichthys flesus) from the Mersey Estuary (UK)—a continuing problem

Vitellogenin (VTG) plasma concentrations were measured in flounder (Platicthys flesus L.) caught in two neighbouring UK estuaries between autumn 1997 and summer 2000. As found in previous studies, male and immature female flounder that were caught in the Mersey, but not in the Dee, had abnormally elevated concentrations of VTG in their plasma—evidence of the presence of natural and synthetic estrogens and/or xenoestrogens in the Mersey. The present study reveals a marked seasonal cycle in VTG concentrations in males. In late spring and summer, male flounder in the Mersey have relatively low concentrations of VTG (μg mL−1 range). However, in mid-winter, mean concentrations were as high as 5 mg mL−1. There is also evidence that there was a lessening in the degree of estrogenic endocrine disruption between 1996–1997 (the period of the initial studies on the Mersey) and 1998–2000 (the period covered by the present study). Only 0.5% of the fish contained ovotestes (intersex condition).