A TERATOGENIC DEFORMITY INDEX FOR EVALUATING IMPACTS OF SELENIUM ON FISH POPULATIONS

This paper describes a method for using teratogenic deformities in fis h as the basis for evaluating impacts of selenium contamination, Terat ogenic deformities are reliable bioindicators of selenium toxicosis in fish. They are produced in response to dietary exposure of parent fis h and subsequent deposition of selenium in eggs. There is a close para llel between selenium concentrations in eggs, incidence of teratogenic deformities in larvae, and magnitude of reproductive failure, Using t hese relationships, an index was developed for teratogenic-based asses sment of impacts to fish populations, The index is composed of three r atings that signify increasing levels of terata-induced population mor tality: 1, negligible impact (<5% population mortality); 2, slight to moderate impact (5-20% population mortality); 3, major impact (>20% po pulation mortality). Each rating is based on the anticipated populatio n-level impact of the corresponding degree of mortality. Teratogenic-b ased impact assessment provides a conclusive cause-effect linkage betw een the contaminant and the fish. It is particularly useful for verify ing selenium-induced impacts on reproductive success because poor repr oduction can be caused by many things-i.e., fluctuating water levels, nest predation, food shortages, poor recruitment, etc. The index given here should be a useful tool for evaluating the effect of selenium on fish populations. Moreover, application of this technique may save co nsiderable time and money by identifying the most efficient use of man power and funds early in the assessment process. (C) 1997 Academic Pre ss.