Periodic Report Summary 1 - ETAA (Evolution of Tolerance to an Anti-Androgen.) The overriding aim of this project was to determine whether sub-lethal exposure to chemicals that mediate their effects via the endocrine system (endocrine active chemicals; EACs) could influence evolution in fish populations. EACs are known to induce reproductive abnormalities in a range of vertebrates and there is evidence that chronic exposure of rivers and lakes can lead to population declines in wild fish populations but the longer-term consequences of such declines are unknown. Through measuring phenotypic variation in the reproductive responses of fish to endocrine active chemicals this project aimed to evaluate the potential for EAC tolerant fish populations to evolve through natural selection.Prior to addressing the main objectives it was necessary to establish a working aquaria along with the necessary licences; to establish a breeding population of wild-sourced fish; and to recruit a PhD student to the project. These initial steps were all successfully completed and the student along with Master students worked on developing the initial protocols and baseline datasets to support the project. During this period the investigator was also successful in obtaining a knowledge-exchange grant that provided the opportunity to develop new collaborations within government involved in development of regulations of EACs. The investigator was also successful in securing a promotion to a new post at a research-intensive University. Unfortunately, however, the PhD student did not wish to transfer Universities and because there would be delays to the project whilst a new aquaria was established the decision was taken to terminate the project. Whilst the research project itself has not progressed to meet all of the original aims, the fellow has been very successfully re-integrated into the European research establishment.