Oestrogenic effects in wild fish: comparing contemporary and historical impacts - summary
Published 30 October 2020
Applies to England
© Crown copyright 2020
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1. Chief Scientist’s Group research summary
The results of a new study of wild roach in English rivers indicate that oestrogenic contaminants continue to occur at levels sufficient to produce a biological response in fish in rivers across the country.
The oestrogenic effects observed – the feminising of male fish (termed intersex) – result from exposure to effluents from wastewater treatment works, which can contain natural and synthetic oestrogens originating from human excretion and the breakdown of industrial detergents.
Previous studies from the 1990s/2000s had shown that oestrogenic (feminising) effects were common in UK roach populations. The new study has revealed that feminisation of males is still occurring at the same sites and remains at similar levels in most locations. However, there are indications that concentrations of oestrogens may be lower than historical levels. This could be associated with water company investments to improve waste water effluent treatment.
These findings have implications for the nationwide monitoring and regulating of oestrogenic contaminants to ensure the health of fish populations and other river life.
1.1 Method
The new investigation was undertaken in the autumn of 2017 and entailed a survey of roach at a small number of sites (10) selected from a total of 73 sites for which historical data was available.
The roach were then analysed to address 3 specific research questions;
- What are the current levels of intersex (and other oestrogenic effects) in wild roach at the sites visited?
- How do current levels of intersex compare with those observed from previous studies undertaken at the same sites in the 1990s /2000s?
- What are the possible explanations for any differences found between current and historically reported levels of intersex in roach populations?
In addition to the well-established oestrogenic exposure and impact indicators (plasma vitellogenin (VTG), ovotestis and feminised ducts), the genetic sex of the sampled fish was also determined to confirm whether intersex fish were feminised males or masculinised females, and to determine the possibility of fully sex-reversed fish
1.2 Results
The results of this latest field survey illustrate that feminisation in wild male roach is still a widespread phenomenon, with intersex males present at 60% of the sites sampled in 2017. For the majority (80%) of sites, the frequency of intersex has not significantly changed compared with historical surveys.
The results also provide some indication of improvement compared with historical samples. No male fish were observed to have feminised ducts; this was observed at 94% of sites in the historical analyses. There was also a significant reduction in plasma VTG in males sampled at 7 of the 10 sites surveyed compared to historical analysis, though levels remain elevated above ‘natural’ levels.
Collectively, the findings of this study are suggestive of a reduction in environmental exposure to oestrogenic substances but with continued impacts in male fish associated with chronic exposure, albeit at lower concentrations than those occurring historically.
A reduction in exposure is consistent with infrastructure upgrades at waste water treatment works, but there was insufficient chemical monitoring data at the fish sampling sites to prove this link.
It should be emphasised that the 2017 survey was much smaller in scale than previous surveys and therefore is not as representative of the whole of England.
Recommendations from this research include more extensive periods of fish collection, greater geographical coverage and the co-location of fish and chemical sampling data. This would improve statistical confidence in results and facilitate an understanding of the links between specific chemicals and observations of biological effects.
1.3 Publishing details
This summary relates to information from project SC170001, reported in detail in the following output:
Report:
SC170001
Title:
Oestrogenic effects in wild fish: comparing contemporary and historical impacts
March 2020
Project manager:
Katie Whitlock, Paul Whitehouse, Research, Analysis and Evaluation
Research Contractors:
Brunel University London,
Kingston Lane, Uxbridge,
Middlesex,
UB8 3PH
01895 274000
University of Exeter,
Stocker Road, Exeter,
Devon,
EX4 4PY
01392 661000
This project was funded by the Environment Agency’s Water Quality team and managed by the Research, Analysis and Evaluation group, which provides scientific knowledge, tools and techniques to enable us to protect and manage the environment as effectively as possible.
Enquiries:
research@environment-agency.gov.uk
© Environment Agency