Bio-markers for egg quality determination in cyprinid fish

The present study investigated potential bio-markers (ovarian fluid parameters, egg weight and weight increase during water hardening, biochemical egg composition, egg enzyme activities) for egg quality determination in the common carp (Cyprinus carpio), the silver carp (Hypophthalmichthys molitrix), the grass carp (Ctenopharyngodon idella) and the bleak (Chalcalburnus chalcoides). For all investigated species, the study revealed highly significant correlations between the egg fertilization rate and the weight of water-hardened eggs, the percent weight increase during water hardening and the ovarian fluid pH, protein concentration, and aspartate aminotransferase activity. The fertilization rate was further correlated with the activities of malate dehydrogenase and pyruvate kinase of the eggs, and in C. calpio and Cha. chalcoides with the respiration activity, too. Investigated biochemical parameters of the eggs (protein, peptides, fructose, galactose, glucose, non-esterified fatty acids, esterified fatty acids, total DNA and RNA) were not correlated with the fertilization rate. The possible use of the analysed parameters for prediction of egg quality during short-term storage was also investigated in C. carpio and Cte. idella: during short-term storage for 4 h at 4 degreesC, the fertilization rate significantly decreased. Also, the weight of the eggs after water hardening, the percent weight increase due to water hardening and the ovarian fluid pH and ovarian fluid aspartate aminotransferase changed in comparison to fresh samples and were highly significantly correlated with the fertilization rate. In contrast, the biochemical composition of the eggs (protein, peptides, fructose, galactose, glucose, non-esterified fatty acids, esterified fattyacids, total DNA and RNA) and egg enzyme activities (phosphofructokinase, pyruvate kinase, protease, lipase, NAD-dependent malate dehydrogenase, respiration rate, NADP-dependent isocitrate dehydrogenase, aspartate aminotransferase) remained constant. (C) 2001 Elsevier Science B.V. All rights reserved.