Ectoparasite induced changes in epidermal mucification of the brown trout, Salmo trutta L.

The apparent effects of environmental factors on skin structure in hatchery-reared brown trout are shown to be mediated by the influence of these factors on the skin parasite population. The presence of ectoparasites promotes a reduction in the concentration of epidermal mucus-secreting goblet cells, the magnitude of which is related to the intensity of infection

Evaluation of flow cytometry as a method for quantification of circulating blood cell populations in salmonid fish

Flow cytometry was used to estimate the proportions of different blood cell types in brown and rainbow trout. On the basis of forward light scatter and 90° side scatter three populations were differentiated. The relative abundance of these cells correlated with that of erythrocytc (r2= 0.994), lymphocyte plus thrombocyte (r2= 0.676) and neutrophil populations (r2= 0.571) enumerated by direct microscopy. By density gradient separation of cells, cell sorting and acridine orange staining it was confirmed that these cell types could be assigned to the populations detected. Changes in blood cell populations were monitored by flow cytometry in a group of experimental fish placed under confinement stress. Flow cytometry proved to be a rapid and reliable method for monitoring cell population dynamics in fish blood