A procedure is described for continuous flow bioassays on sensitive developmental stages of fish and other aquatic species. Environmental toxicants may be screened for teratogenic and other embryopathic effects (e.g., mortality, locomotor impairment) on eggs, embryos, and early juvenile stages. Toxicant concentration may be regulated down to 1.0-0.1 ppb for an exposure period extending from fertilization through 4-7 days posthatching. Bioassays may be performed with either natural or synthetic water, and standard physicochemical parameters (e.g., temperature, water hardness, pH) can be manipulated independently to determine effects on toxicity. The procedure is suitable for use with a wide range of fish and amphibian species, including rainbow trout, channel catfish, largemouth bass, leopard frog and others. Concerning the toxic effects of many environmental trace contaminants, embryonic and early juvenile stages constitute the critical sensitive links in the life cycles of many aquatic animal species. Reproductive potential of aquatic animals may be severely restricted or abolished by trace levels of toxicants which are harmless or sublethal to most adult organisms.

Final technical report, Apr. 1977. Performing organization: University of Kentucky. EPA Contract no. 68-01-4321. Issued Apr. 1977. Includes bibliographical references (pages 56-59).