Qualification of spontaneous undirected locomotor behavior of fish for sublethal toxicity testing. Part II. Variability of measurement parameters under toxicant-induced stress

Spontaneous locomotor behavior of semiadult zebra fish (Brachydanio rerio) was recorded under sublethal short-term exposure to the anionic technical s urfactant, linear alkylbenzene sulfonate (C10-13-LAS) and cadmium in single compound tests using an automated video-monitoring and object-tracing syst em. Vertical position and swimming velocity in the horizontal and vertical directions were used as behavioral measurement parameters. Data were analyz ed by different statistical methods. In pairwise comparisons, consistent, s tatistically significant, and toxicant-induced alterations of locomotor beh avior were observed only for test concentrations, which also caused aspecto ric symptoms of intoxication. This comparatively low sensitivity of the beh avioral indication criteria was related to high variation in the measuremen t parameters and corresponding high, minimum detectable, statistically sign ificant, and toxicant-induced deviations. In contrast, results obtained by regression analysis showed significant trends in locomotor activity over th e range of toxicant concentrations tested. Thus, our findings support the i nappropriateness of no observed effect concentrations and the lowest observ ed effect concentrations as summary measures of toxicity and indicate that the regression analysis approach is superior to the analysis of variance ap proach.