Small species of fish have been used in many studies because their size allows large numbers to be kept in a limited
space and their short life cycles provide the opportunity to examine multiple generations (DeVita 1984; May and others
1987a,b). Fish have also been used to investigate carcinogenicity and toxicity of various compounds (Iwan and
Cella 1981; Ishikawa and others 1984; EPA 1989, 1991). Japanese medaka and zebrafish transgenic specimens are
being used to evaluate the roles of multiple genes in development (Streisinger and others 1981; Brenner and others 1993;
Chen and others 1995)