Abstract <p>The hematological characteristics of the circulating blood of the golden grey mullet (<i>Chelon auratus</i> Risso, 1810) in the first 3 years of life were studied. The material was obtained simultaneously in March–April at the mullet fish farm (settlement of Belenkoe, Odessa oblast). It was found that in the first year of the life of the golden mullet, an active production of circulating erythrocyte mass occurs. The level of polychromatophilic normoblasts, reflecting the rate of erythropoietic processes in hematopoietic tissue, reaches maximum values in the peripheral bloodstream of fingerlings. Intracellular hemoglobin synthesis occurs at a lower rate. This is accompanied by the appearance of hypochromic erythrocytes in the blood. The value of the mean cellular hemoglobin content (<i>MCH</i>) is at a minimum level of 28.9 ± 0.8 pg (in third-year fish, 37.1&#xa0;± 0.8 pg). The blood of fry and yearlings is dominated by large red blood cells (96.9 ± 4.1 mm³) with high values of the nuclear cytoplasmic ratio (<i>NCR</i>): 0.121 ± 0.011. The <i>NCR</i> index decreases by the second year of life as the <i>MCH</i> increases (<i>R</i>² = 0.851). In the blood of yearlings, there is a high content of erythrocyte abnormalities (up to 14% of erythroid cells): dacryocytes, cells with invagination of the nucleus, erythrocyte shadows. The presence of dacryocytes in the blood of this age group reflects the development of hypoxia. It follows from the presented results that the first year in the life cycle of the golden grey mullet is the most critical. This should be taken into account when breeding this species in fish farms.</p>