Assessment of water turbidity for evaluation of rainbow trout (Oncorhynchus mykiss) egg quality Mariola Wojtczak a , Radosl C aw Kowalski a , Stefan Dobosz b , Krzysztof Goryczko b,c , Henryk Kuz ´minski b , Jan Glogowski a , Andrzej Ciereszko a, * a Institute of Animal Reproduction and Food Research, Polish Academy of Sciences, 10-747 Olsztyn, Tuwima 10, Poland b Department of Salmonid Research, Inland Fisheries Institute, Rutki, 83-300 Z ˙ ukowo, Poland c Department of Fish Biology and Culture, University of Warmia and Mazury, 10-718 Olsztyn, Oczapowskiego 5, Poland Received 30 August 2003; received in revised form 28 February 2004; accepted 2 March 2004 Abstract Upon contact with water, two types of rainbow trout ova can be distinguished: ova causing turbid water and ova that do not cause such an effect. The objective of this study was to evaluate the quality of eggs in relation to their ability to cause water turbidity. The biochemical characteristics of ovarian fluid were also determined. When water was used as the fertilization medium, a clear difference in fertilization rate was observed between both types of ova. The percentage of eyed embryos for eggs causing turbid water (15.7F3.0%) was significantly lower than eggs causing non-turbid water (67.2F9.6%). No differences were found when salt solutions were used as the fertilization medium. Protein and lipid concentrations of ovarian fluid collected from eggs causing turbid water were significantly higher than in samples collected from eggs that did not cause turbid water. Our results indicate that the turbidity of water was caused by the coagulation of water with egg contents. In our opinion, performing turbidity tests might be critical for successful fertilization when water is used as the fertilization medium. In such instances, ova causing turbid water must be discarded. The test for turbidity should provide valuable data concerning initial quality of eggs. D 2004 Elsevier B.V. All rights reserved. Keywords: Ova; Yolk; Ovarian fluid; Fertilization; Rainbow trout 0044-8486/$ - see front matter D 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.aquaculture.2004.03.001 * Corresponding author. Tel.: +49-89-5357426; fax: +49-89-5357421. E-mail address: acieresz@pan.olsztyn.pl (A. Ciereszko). www.elsevier.com/locate/aqua-online Aquaculture 242 (2004) 617 – 624