Red Blood Cell Indices for Rainbow Trout (Oncorhynchus mykiss) Reared in Cage and Raceway Culture

Abstract

¤ehulka J, Adamec V: Red Blood Cell Indices for Rainbow Trout (Oncorhynchus mykiss Walbaum) Reared in Cage and Raceway Culture. Acta Vet Brno 2004, 73: 105-114. In this study, 161 immature female rainbow trout of weight 331 ± 30 g, raised in cage culture 291 m above sea level at water temperature 17 ± 3 oC, were used to calculate reference (physiological) haematology values for red blood cell indices. Red blood cell counts (RBCc), haematocrit values (Hct), haemoglobin concentrations (Hb), mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH) and mean corpuscular haemoglobin concentration (MCHC) were measured and analyzed. The calculated intervals of the reference ranges between the lower and upper quantiles were: RBCc 0.87 ‐ 1.34 T . l-1, Hct 0.36 ‐ 0.554, Hb 64 ‐ 107 g . l -1, MCV 347 ‐ 501 fl, MCH 60 ‐ 92 pg and MCHC 0.15 ‐ 0.21. Multiple correlation indices obtained from cage culture fish to determine effects of time (Day), water temperature (WT), dissolved oxygen (O 2 ), oxygen saturation level of the water (OSW), chemical oxygen demand (CODMn), biological oxygen demand (BOD5) and NH4+ were the following: RBCc was explained by Day and QOSW with coefficient of correlation r = 0.611, Hb was explained by QBOD5 and QNH4 + with correlation r = 0.783 and MCHC was explained by COD Mn , QDay and QO 2 with correlation r = 0.743. Fish from cage culture had significantly greater red blood cell indices (P = 0.01 and P = 0.0000, respectively) than fish from flow-through tanks 651 m above sea level, water temperature 9 ± 2.5 oC and equal nutrition. The results have shown that fish farming technology, varying physical and chemical properties of water and availability of natural food may influence erythropoiesis in caged fish. Red blood cell counts, haemoglobin, haematocrit, mean corpuscular volume, mean corpuscular haemoglobin, mean corpuscular haemoglobin concentration, reference range Rainbow trout farming in cage culture is a traditional means of aquaculture in the Czech Republic. It is primarily focused on productive utilization of multi-purpose fresh water retention lakes. In comparison with the classical ways of trout farming using raceway culture it allows reduced energy losses in the fish and offers opportunities to exploit resources of natural food. Irregular upward temperature fluctuations accompanied by oxygen dynamics and the presence of a wide spectrum of wild fish species living naturally outside cages present a risk to fish health. Haematological tests to provide information about the state of erythropoiesis. Previous haematological studies of nutritional effects (¤ehulka 1984ab, 1989, 2000), infectious diseases (¤ehulka 2002a) and pollutants (¤ehulka 2002b) brought knowledge that erythrocytes are a major and reliable indicator of various sources of stress. Erythrocytes reflect the state of the organism over a prolonged period of time. Also, the outcome of a test is only slightly influenced by the timing of sample collection. From a clinical haematology standpoint, knowledge of the reference ranges of red blood cell indices is vital for impartial assessment of the samples. These values were previously described in work by Haider (1970, 1971, 1973), M cCarthy et al. (1973, 1975), Sniezsko (1961), Wedemeyer and N elson (1975), Miller et al. (1983) and Haley and Weiser (1985). The objective of the current study of fish from cage culture was: (1) to define reference