2019 Volume 22 Issue 1 Pages 1-11
In this study, we assessed the population-level impacts of 4-nonylphenol (NP) on medaka fish based on a population matrix model developed and results of the medaka extended one-generation test (MEOGRT). The concentration-response relationships for the number of fertilized egg and the survival rate were estimated from results of the MEOGRT and were incorporated into the population model. Although the lowest observed effect concentration (LOEC) in the MEOGRT was reported to be 1.27 μg/L NP, the predicted population growth rates at NOEC and even at the maximum test concentration of 89.4 μg/L NP were higher than 1 (358 and 6.2, respectively). We also projected values of mean time to extinction at different concentration levels and corresponding reductions in carrying capacity (K). Based on the comparison of the projected population-level impacts with quantitative criteria used in fishery resource management and IUCN red list categorization, concentrations higher than NOEC can be acceptable. Overall, those results suggest that use of multiple criteria based on individual and population-level impacts rather than a limited number of criteria (such as LOEC and NOEC based on individual-level effects) would be important in ecological risk assessments.
