Assessing Growth Dynamics and Exploitation of Alosa Immaculata (Bennet, 1835) in Relation to Thermal Conditions in the Lower Danube in 2025

This study evaluates the biological and ecological status of the Pontic shad (Alosa immaculata) population during the 2025 spawning migration season in the Galați–Brăila sector of the Danube River. A total of 576 individuals were sampled between March and June 2025. Environmental data, particularly water temperature, were analyzed using the Growing Degree Days (GDD) method to quantify the thermal energy available throughout the migration and spawning period. GDD values revealed distinct thermal thresholds that coincide with key physiological transitions, with peak accumulation in April and May supporting intense reproductive activity. Growth parameters were estimated using the Von Bertalanffy Growth Function (L∞ = 34.65 cm; K = 0.48 year⁻¹; Φ’ = 2.76), indicating moderate growth potential. Mortality analysis showed total mortality (Z) at 1.54 year⁻¹, with natural mortality (M = 0.74 year⁻¹) and fishing mortality (F = 0.80 year⁻¹), resulting in an exploitation rate (E = 0.52). The M/K ratio (1.54) suggests moderate population resilience. The integration of thermal and biometric data provides a comprehensive understanding of the species’ biological condition and seasonal patterns. These findings underscore the importance of continuous monitoring and adaptive management to safeguard Alosa immaculata amid increasing environmental and anthropogenic pressures.