Preliminary Data Regarding the Physiological State of <i>Alosa immaculata</i> (Bennett, 1835) During Spawning Migration

ABSTRACT Reproductive migration in anadromous fish involves complex physiological adjustments to support intense metabolic and reproductive demands. In the case of Alosa immaculata , a key migratory species of the lower Danube River, these adaptations can be assessed through hematological and biochemical indicators. During the 2025 spawning season, Pontic shad individuals were sampled in the Chiscani–Galați sector and evaluated for biometric characteristics, sex ratio and physiological status. The results showed a predominance of mature females, with mean individual body weight of 0.21 ± 0.04 kg and total length of 29.72 ± 1.66 cm. Haematological analysis revealed elevated haematocrit (44.13% ± 5.35%) and haemoglobin concentrations (15.75 ± 2.73 g/dL), especially in females at advanced reproductive stages. RBC count and erythrocyte indices (MCV, MCH, MCHC) reflected physiological adjustments to the energetic demands of migration and gonadal maturation. Biochemical profiles indicated adequate nutritional and immune status, with balanced protein values and mineral levels supporting reproductive readiness. Statistical correlations between haematological and biochemical parameters suggested coordinated physiological responses during the reproductive phase. These findings demonstrate that haematological profiling provides a valuable tool for assessing the physiological and adaptive status of A. immaculata during migration and supports its relevance for ecological monitoring and conservation strategies.