Abstract. The purpose of the present studywas to investigate some basic biochemical and chemical parameters of pikeperch (Sander lucioperca L.) yearlings reared in ponds after wintering. The investigation has been carried out in the Institute of Fisheries and Aquaculture, Plovdiv. The fish included in the study were randomly selected from one pond, with area of 0.40 ha. Blood samples were collected from 10 pikeperches with average weight from 80 to 100 g. Blood biochemical parameters were individually analysed. For hemoglobin determination, blood was anticoagulated with sodium citrate. Samples for body tissue о analysis (without the head and viscera) were collected from 4 fish, autoclaved and used for analysis of water content, % (drying at 105 С, 24 h; Bulgarian State Standard – SR ISO 5984), protein content, % (Kjeldahl method, Bulgarian State Standard – SR ISO 5983 semi-automated DK 6 digester unit and UDK 132 o distillation system, Velp Scientifica), fats (%) by the method of Smidt-Boudzynski Ratzlaff and ash (%) by burning in a muffle furnace at 550 С, BSS – SR ISO -1 -1 -1 6496. The average blood serum total protein was 66.1±0.12 g.l , blood glucose concentration was 92.8±3.42 mg.100 ml (5.15 mmol.l ) and average -1 hemoglobin content was 44.7±0.33 g.l . The average protein content in analysed fish samples was 16.65±0.23 %. Protein content was the highest among studied dry matter components, followed by the ash (1.97±0.06 %) and fat content (0.84±0.03 %). The levels of blood serum total protein, blood glucose and hemoglobin content as well as body composition parameters - water, protein, fat and ash of pikeperch fingerlings (Sander lucioperca L.) after wintering reflect the specific equilibrium of plastic and energy substances after the winter period, with no deviations from the reference ranges.