ABSTRACT
This chapter deals with the action of chronic levels of pollutants that do not necessarily affect survival but do impact the process of reproduction. The reproductive strategies of fishes determine the behavior after eggs are laid. The formation of eggs and sperm, the first step in reproduction, is initiated by the environmental cues mentioned. These work through the hypothalamus which acts on the pituitary by way of gonadotropin-releasing hormones (GnRH). Estrogenic hormones from the ovary stimulate vitellogenin production and its uptake into the ovum and are stimulated by gonadotropins I. Prespawning female rainbow trout show higher levels of testosterone than males, probably because this hormone is a precursor for estradiol. The various stages of embryonic development show different sensitivities and even different qualitative effects of a pollutant insult. Early embryonic development before gastrulation has been completed is the most sensitive stage for various components of petroleum and for mercury.
