The first record of brook trout (Salvelinus fontinalis, Salmonidae) blood cell characteristics and hematological profile: the influence of fish sex on leukocyte count

Hematological parameters of fish are useful for diagnosing pathophysiological conditions associated with metabolic perturbations in fish and therefore act as a non-specific biomarker of acute and chronic stress in the natural habitat and in aquaculture. Salmonid fish are of great importance in aquaculture; however, hematological studies of these species are scarce. This study presents the first set of data for the complete hematological profile of brook trout ( Salvelinus fontinalis , Salmonidae). In total, seven blood cell types were identified and their characterization, range, size/surface area, and the leukocyte differential count are presented. Large numbers of immature erythrocytes and two subtypes of thrombocytes (round and prolate) were present in blood. Lymphocytes were the dominant leukocytes, followed by segmented neutrophils. Total leukocyte and segmented neutrophil counts were higher in the blood of male than female fish ( P