The overall aim of the project is to examine whether exposure of roach populations to oestrogenic WwTW effluents over multiple generations has resulted in genetic selection, and the impact of selection on the susceptibility in male fish to develop oestrogen-induced effects associated with negative fitness consequences. Specifically this data was generated to construct a transcriptome and subsequently identify genetic differences (single nucleotide polymorphisms -SNPs) in (1) specific (candidate) genes that we know are important in oestrogen signalling of reproductive (and other life) processes and (2) control genes for which there is no evidence for involvement in oestrogen signalling or reproductive processes. These data will then be used to test whether candidate genes have signatures of selection in roach populations confined to rivers with a high proportion of estrogenic effluent.