The aim of the study was to determine the impact of diet and sex on the hematological and blood plasma biochemical profiles and the liver histology of pikeperch, Sander lucioperca (L.) reared in recirculating aquaculture systems (RAS) (initial mean body weight (BW) 1.35 kg). The proximate composition of the two commercial feeds used were (protein/lipid/nitrogen-free extracts) (P/L/NFE)) P505/L118/NFE294 g kg−1 (group I) and P471/L141/NFE290 g kg−1 (group II). Neither diet nor sex had a significant impact on final fish body weight (≈ 2.0 kg). Sex was noted to significantly impact glucose content (Glu – higher in males) and cholesterol (Chol – higher in females) in the blood plasma. Diet was confirmed to have a significant impact on levels of hematocrit (Ht), hemoglobin (Hb), and mean corpuscular hemoglobin (MCH), and the values of these indicators were higher in group I. Sex had a significant impact on Ht, Hb, MCH, and mean corpuscular hemoglobin concentration (MCHC), with higher values in male pikeperch. Diet and sex had significant impacts on the values of the pikeperch hepatosomatic index (HSI), hepatocyte size and that of their nuclei, and the values of the nucleocytoplasmic index (NCI).
