The effect of temperature on non-specific defence parameters of three strains of juvenile Atlantic halibut (Hippoglossus hippoglossus L.).

The effect of temperature (8, 12, 15 and 18 degrees C) on a variety of non-specific defence and haematological parameters was examined in three geographically distinct reared strains (Canadian, Icelandic, Norwegian) of Atlantic halibut. The results indicate that temperature exerts a considerable influence on some blood parameters (packed cell volume and the percentage population of leucocytes in peripheral blood) and on some humoral parameters (serum lysozyme activity and serum protein levels) of halibut. A high temperature of 18 degrees C caused a decrease in the number of circulating blood cells and an increase in serum lysozyme levels; effects consistent with those reported within the literature for stress. The different strains of halibut exhibited differing responses with respect to differential counts of peripheral blood lymphocytes and thrombocytes, and to serum protein concentrations, serum lysozyme activity, serum iron content, unsaturated iron binding capacity of serum and O2- production by kidney macrophages.