Does exposure to domestic wastewater effluent (including steroid estrogens) harm fish populations in the UK?

- Fish density data for four species at 38 sites over several years were examined.
- No clear relationship between fish density and wastewater estrogen exposure.
- Temporal variation of Rutilis rutilis (roach) over several years was examined in two rivers.
- No clear negative impact of temporal change in wastewater estrogen exposure on roach.
- Wastewater estrogen exposure is not catastrophic for four common cyprinid species.

Historic fisheries data collected from locations across the UK over several years were compared with predicted estrogen exposure derived from the resident human population. This estrogen exposure could be viewed as a proxy for general sewage (wastewater) exposure. With the assistance of the Environment Agency in the UK, fisheries abundance data for Rutilis rutilis (roach), Alburnus alburnus (bleak), Leuciscus leuciscus (dace) and Perca fluviatilis (perch) from 38 separate sites collected over 7 to 17 year periods were retrieved. From these data the average density (fish/m2/year) were compared against average and peak predicted estrogen (wastewater) exposure for these sites. Estrogen concentrations were predicted using the LF2000-WQX model. No correlation between estrogen/wastewater exposure and fish density could be found for any of the species. Year on year temporal changes in roach population abundance at 3 sites on the middle River Thames and 4 sites on the Great Ouse were compared against estrogen exposure over the preceding year. In this case the estrogen prediction was calculated based on the upstream human population providing the estrogen load and the daily flow value allowing concentration to be estimated over time. At none of the sites on these rivers were temporal declines in abundance associated with preceding estrogen (effluent) exposure. The results indicate that, over the past decade, wastewater and estrogen exposure has not led to a catastrophic decline in these four species of cyprinid fish.

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