Hematological and biochemical profiles of juvenile Siberian sturgeon and Kaluga hybrid (Acipenser baerii × Huso dauricus) reared in recirculating aquaculture systems

This study aimed to establish species-specific reference ranges for physiological parameters in juvenile hybrids of the Siberian and Kaluga sturgeon (Acipenser baerii ♀ × Huso dauricus ♂) raised in recirculating aquaculture systems (RAS). A comprehensive hematological analysis revealed an average red blood cell count of 0.67±0.12×106/μL and a white blood cell count of 2.99±0.25×104/μL. These values are similar to those of other sturgeon species. A study of the leukocyte formula showed the absolute dominance of lymphocytes (86.08%), reflecting the specificity of fish immunity. Meanwhile, eosinophils (6.48%) outnumbered neutrophils (4.84%), a characteristic of the hybrid in study. Young rod-shaped forms (3.30%) were found to dominate among neutrophils, while the pool of eosinophils was mainly represented by mature segmented cells (4.74%). Analysis of the biochemical profile of blood serum revealed stable basic protein metabolic indicators: total protein level was 20.69±2.05 g/L and urea level was 1.61±0.24 mmol/L. Glucose, a key energy substrate, ranged from 1.56 to 3.99 mmol/L. However, high individual variability in enzyme activity (AST, ALT, and LDH) and total bilirubin concentration was observed. These dynamics indicate the increased sensitivity of these metabolic markers to changes in feeding conditions and environmental parameters in the RAS. The summarized data, including the reference intervals for clinical and biochemical blood parameters calculated for the first time, can be used as a physiological norm for monitoring health and diagnosing diseases early in industrial aquaculture.