Effects of stress on blood viscosity and other blood paramenters in striped bass, Morone Saxatilis (Walbaum).

Abstract

The culture of striped bass, Marone saxatilis, for commercial and recreational purposes is a popular form of aquaculture in the United States. However, midsummer mortalities, which could be due to high temperatures and oxygen depletion, have been reported. Cultured fish are exposed to stressful factors such as temperature, transport, and hypoxia. The objective of this study was to investigate the effects of stress on blood viscosity and other blood parameters in striped bass. Thirty-three adult striped bass, weighing between 1040-1800 g, were divided into five groups: control, hypoxia, simulated transport, diseased (henneguya), and temperature. Red blood cell count, white blood cell count, hematocrit, hemoglobin concentration, mean cell hemoglobin concentration (MCHC), mean cell volume (MCV), mean cell hemoglobin (MCH), and plasma protein concentration were determined. Viscosity measurements were determined at 10 different shear rates. At packed cell volumes of 30% and 40%, the simulated transport group had a significant decrease in apparent viscosity as compared to controls at higher shear rates (37.5 S-I, 75 S-I, 150 S-I), whereas the hypoxic group showed a significant increase in apparent viscosity as compared to controls at higher shear rates (37.5 s-l, 75 S-I, 150 S-I). The diseased group showed a significant increase in relative viscosity as compared to controls at higher shear rates. The temperature group at 24°C and 27°C showed a significant increase in apparent viscosity when compared to the controls at higher shear rates. The stress of transporting striped bass in well-aerated water had little impact on apparent blood viscosity. However, hypoxia could be a major cause of midsummer mortalities in striped bass because increased apparent viscosity could lead to decreased blood flow in the systemic circulation, thereby decreasing oxygen delivery to tissues. This research was conducted with financial assistance from the Emporia State University Research and Creativity Committee.