The growth response in fish chronic and early life stage toxicity tests: A critical review

Toxicity data from 25 years of fish life cycle chronic, partial chronic and early life stage tests are examined to determine the utility of the standard fish chronic toxicity endpoints, in particular the growth response, to chemical hazard evaluations. The 173 tests include exposure to metals, pesticides, unclassified organics, inorganic compounds, detergent chemicals and complex effluents. Fry survival was significantly reduced in 57% of all tests at the lowest effect concentration. Fry growth was reduced in 36% and egg hatching in 19% of the tests. Only 60% of the tests include exposure of adult organisms. Reproduction was reduced in 30% of these tests. Adult survival (13%) and growth (5%) were seldom reduced at the lowest effect concentration. Fry survival and growth were very often correlated as equally sensitive. Fry growth was the single most sensitive response in only 14% of the tests reported. In the absence of the growth response data for these 20 chemicals/effluents, the fry survival data would have provided MATC values within a factor of 2 to 7 (x⋍3). The conclusion is that, as presently derived, the growth response could be deleted from routine applications of the fish early life stage test. The net result would be a significant reduction in the duration and cost of screening tests with no appreciable impact on estimating MATCs for chemical hazard assessments. Possible explanations for the insensitivity of the standard growth response, alternatives, and other relevant observations of this data base are discussed.