Abnormalities in the reproductive health of flounder Platichthys flesus exposed to effluent from a sewage treatment works

A large number of substances in daily use are now known to mimic the female sex hormone oestrogen. These include DDT, some PCBs, components of food packaging materials and certain alkylphenolic substances which may arise from alkylphenol polyethoxylates used in detergents, paints and cosmetics. Indicators of reproductive health including gonad morphology, hepatosomatic index (HSI) and serum levels of the egg protein vitellogenin (VTG) were determined for wild populations of the flounder, Platichthys flesus. Fish were obtained from three sites in northern England; the Solway Firth which receives only low levels of sewage effluent and two sites in the Tyne Estuary which receives effluent from a major sewage treatment works and a number of industrial discharges. Four lines of evidence suggest that the reproductive health of flounder is being influenced by exposure to oestrogenic substances. 1. Male fish with serum containing VTG, a reliable bio-indicator of oestrogen exposure, were recorded from all the sites studied. Frequency of occurrence was lowest (20%) in the Solway population and reached 60% at one of the sites in the Tyne. 2. Serum concentrations of VTG were also highest in fish from the Tyne stations. 3. Male fish from the Tyne also displayed high levels of testicular abnormalities (up to 53% of fish) compared to the Solway population (no abnormalities recorded) and 4. the HSI of male flounder from the Tyne were significantly greater than for males from the Solway site. This study is the first to demonstrate oestrogenic effects on a wild population of a marine fish exposed to sewage effluent. The high levels of abnormalities recorded raises concerns about the long term health of fish populations in areas receiving large volumes of effluent, these are discussed.