Development of fish tests for endocrine disruptors

International concern over endocrine active substances (EASs) has led to intensive research programs to establish fish reproductive and developmental toxicity tests for use in environmental (ecological) risk assessment. This chapter gives an overview of key themes of in vivo ecotoxicology research, including fish screening assays, partial life-cycle tests (the draft Organization for Economic Cooperation and Development (OECD) fish reproduction test and the new fish development test) and fish full life-cycle tests. In the context of the OECD test guidelines program, fish species of primary interest include fathead minnow, medaka, and zebrafish, while guppy, rainbow trout, sheepshead minnow, and three-spined stickleback are also of scientific importance. Critical factors for evaluation include baseline reproductive biology and definition of EAS sensitive life-stages. For regulatory applications, a critical review of existing fish EAS data suggests that apical adverse effect endpoints, namely development, growth and reproduction (e.g., fecundity, fertilization rates and hatching success) should be used to derive predicted no effect concentrations (PNECs) for the environmental risk assessment of EASs. In support of these apical adverse effect endpoints, biomarker responses (e.g., vitellogenin, gonadal-somatic index, and gonad histopathology) should be used to provide mechanistic data, compare species (e.g., cyprinids vs. salmonids) and allow extrapolation between laboratory and field studies.