Millimolar Quantities of Sodium Salts Used as Prophylaxis during Fish Hauling

Abstract

Abstract Rainbow trout provided with chronic dorsal aortic cannulae were placed in a tank with uncannulated fish at a density of 48 kg/m³ (3 lb/ft³). Following 4 h of simulated hauling conditions the principle blood buffer, HCO3 - (i.e., 90% of arterial plasma total CO² content) was reduced by 22% and after recovery for 2 h arterial pH and HCO3 - were significantly below pre-haul levels. Introduction of either NaCl or, in particular, Na2SO4 or NaHCO3 into the hauling water (final concentration, about 10 mM) helped ameliorate the acid-base disturbances associated with handling and hauling. The addition of NaHCO3 or Na2SO4 totally offset the decrease in blood buffering capacity associated with fish handling and hauling; in fact, a significant increase in blood buffering capacity was evident 2 h after fish were returned to the raceway. Addition of Na2SO4 or NaHCO3 to water during routine fish hauling may help to reduce the effects of handling, crowding, and external stressors.