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(59-04) Assessing recruitment success of brown trout in two streams by using early life stage tests. Luckenbach, Till*,1,2, Kilian, Maja1,2, Triebskorn, Rita1,3, Oberemm, Axel4, 1 Animal Physiological Ecology, University of Tübingen, Tübingen, Germany2 Institute for Freshwater Ecology and Inland Fisheries, Berlin, Germany3 Steinbeis-Transfer Center for Ecotoxicology and Ecophysiology, Rottenburg, Germany4 Institute of Health Protection of Consumers and Veterinary Medicine, Berlin, Germany ABSTRACT- Early life stage (ELS) tests were performed between 1995 and 2000 in order to evaluate embryotoxic potentials for brown trout (Salmo trutta f. fario L.) in two streams with different pollution degrees in southwest Germany. Various exposure experiments were conducted in the laboratory, in by pass-systems under semi-field conditions, and in the field in order to address different levels of complexity of environmental conditions and to study the impact of xenobiotic contamination, temperature, and sediments on the developmental success. Examined endpoints were mortality, developmental rates, heart rates, hatching process, and growth. Additionally, effects of water from the polluted stream on fertilization of brown trout eggs were determined. In the more polluted stream, xenobiotics were found to cause developmental effects and viability of exposed eggs was drastically reduced by sedimentation of water-borne fine solids. Additionally, fertilization rates of trout eggs were significantly decreased in water of the more polluted stream. In the less polluted stream, low water temperature and infestations by protozoic ectoparasites caused mortality of trout embryos. In this stream, pollution and sediment effects were not observed. Results made evident that chronic stress mediated by xenobiotics and sediments in the more polluted stream causes high losses over time and affects survivors, thus drastically disturbing recruitment success of brown trout. In the less polluted stream, low temperatures and parasite infections were episodic events causing high losses, but may be tolerated on the population level due to the absence of chronic stress and good condition of survivors. Key words: recruitment, brown trout, stream pollution |
