Endocrine toxicants and reproductive success in fish

There is compelling evidence on a global scale for compromised growth and r eproduction, altered development, and abnormal behaviour in feral fish that can be correlated or in some cases causally linked with exposure to endocr ine disrupting chemicals (EDCs). Attributing cause and effect relationships for EDCs is a specific challenge for studies with feral fish as many facto rs including food availability, disease, competition and loss of habitat al so affect reproduction and development. Even in cases where there are physi ological responses of fish exposed to EDCs (e.g., changes in reproductive h ormone titres, vitellogenin levels), the utility of these measures in extra polating to whole animal reproductive or developmental outcomes is often li mited. Although fish differ from other vertebrates in certain aspects of th eir endocrinology, there is little evidence that fish are more sensitive to the effects of EDCs. Therefore, to address why endocrine disruption seems so widespread in fish, it is necessary to consider aspects of fish physiolo gy and their environment that may increase their exposure to EDCs. Dependen ce on aquatic respiration, strategies for iono-osmotic regulation, and mate rnal transfer of contaminants to eggs creates additional avenues by which f ish are exposed to EDCs. This paper provides an overview of responses obser ved in feral fish populations that have been attributed to EDCs and illustr ates many of the factors that need consideration in evaluating the risks po sed by these chemicals.