Aquatic Toxicology 71 (2005) 49–59 Impact of PCB mixture (Aroclor 1254) and TBT and a mixture of both on swimming behavior, body growth and enzymatic biotransformation activities (GST) of young carp (Cyprinus carpio) Katja Schmidt ∗ , Georg B.O. Staaks, Stephan Pflugmacher, Christian E.W. Steinberg Department of Fish Biology and Ecology, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, M¨ uggelseedamm 301, D-12587 Berlin, Germany Received 12 December 2003; received in revised form 8 June 2004; accepted 14 October 2004 Abstract The sensitivity of carp to chronical stress due to single and combined mixtures (each 50%) of TBT and PCB was evaluated under laboratory conditions. And concluded, mixed exposures were partially more or less toxic than single ones. Xenobiotic stress led to both decreased mean daily swimming speed and an increased mean swimming speed during darkness. Also a decreased preferred swimming depth (nearer to the surface) during nighttime was observed. We found approximately synergistic effects of TBT and PCB in swimming behavior of carp exposed to those mixtures. PCB did not affect the body growth significantly, TBT-stress led to a decreased body growth and the exposure to PCB–TBT mixture caused an approximately additive decrease of body growth. Measurement of biotransformation potential measured as GST enzyme activity showed both increasing or decreasing activity levels after exposure to single and mixture chemical combinations (approximately additive, antagonistic and synergistic). Nevertheless, we had to conclude that all methods tested were useful to screen subacute effects of single as well as mixed xenobiotic chemicals on carp, which is the prerequisite for an investigation of samples taken from the environment. © 2004 Elsevier B.V. All rights reserved. Keywords: Xenobiotic mixture; Synergistic effects; PCB; TBT; Swimming behavior; Biotransformation 1. Introduction As a result of the pollutants transport from indus- trial areas into the environment and their chemical ∗ Corresponding author. Tel.: +49 30 64181625; fax: +49 30 64181682. E-mail addresses: schmidt@igb-berlin.de, katjaschmidt1@hotmail.com (K. Schmidt). persistence, many freshwater ecosystems are faced with spatially or temporally alarming high levels of xenobiotic chemicals (Fent, 1998; Brack et al., 2002; Diez et al., 2002). Typical man-made pollutants are polychlorinated biphenyles (PCB) and tributyltinchlo- ride (TBT), which were selected for our present studies. Both TBT and PCB are known to be toxic and several effects have been reported for fish (Svobodova et al., 1994; Grinwis et al., 1998). TBT is widely used in 0166-445X/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.aquatox.2004.10.012