First report of intersex roach residing in Irish rivers downstream of several wastewater treatment plants

Endocrine disrupting chemicals (EDCs) are chemicals that have the ability to mimic or disrupt the endocrine system in wildlife. Many of these EDCs are present in treated Irish sewage effluents and landfill leachate and have recently been identified in Irish rivers. The effects of exposure to EDCs were investigated in Irish brown trout (Salmo trutta), sampled from selected Irish rivers downstream of Irish wastewater treatment plants (WWTPs) with control fish sampled upstream of the same WWTP. The effects were also investigated in Irish roach (Rutilus rutilus) sampled downstream of Irish WWTPs. Control roach were sampled from a pristine salmon fishery river (River Deel) located in the west of Ireland. Histopathological and macroscopic analyses of downstream trout showed no adverse reproductive effects, compared to control fish sampled upstream of the WWTP. Statistically significant (p <0.05) populations of wild roach from three sampled Shannon basin rivers were, however, observed to be phenotypically intersex (ovo-testis) when compared to the control river. This, it is hypothesised, is as a direct result of exposure to WWTP effluents. The results reported herein are the first observations of intersex fish in Irish rivers.