Seasonal variability in the biological characteristics and environmental factors of Sardina pilchardus stock along the eastern Egyptian Mediterranean coast using in-situ and remote sensing techniques

• Biological condition indices varied seasonally with positive allometric growth. • MODIS-Aqua data revealed SST and chlorophyll-a seasonal fluctuation. • Integration of field and satellite data supports fishery environment links. • Findings inform sustainable fisheries management in the southeast Mediterranean. The eastern Mediterranean Sea, particularly along the Egyptian coast, hosts ecologically and economically significant fish stocks that are vulnerable to environmental variability and fishing pressures. This study investigates the seasonal variability of Sardina pilchardus along the eastern Egyptian Mediterranean coast, from Port Said to El-Arish, integrating biological sampling and satellite remote sensing. Field surveys were conducted seasonally from summer 2023 to spring 2024, yielding 1094 specimens collected using standardized purse-seine (Chanchola) methods at geo-referenced coastal landing sites. Biological characteristics including total length (TL), body weight (W), and condition factors (Kn, Kc, Ka) were measured onboard. Length-weight relationships (LWRs) were determined by season, showing high determination coefficients (R² ranging from 0.876 to 0.9736), indicating good fit of the growth model. The allometric coefficient (b) ranged between 3.12 and 3.32, indicating positive allometric growth in all seasons. Complementing the biological data, over 730 MODIS-Aqua satellite images were processed to extract sea surface temperature (SST) and chlorophyll-a (Chl-a) concentrations. Image processing involved SeaDAS 7.5 and MATLAB scripting to mask clouds, subset the study area, and compute seasonal means. SST ranged seasonally between 17 °C (winter) and 29 °C (summer), while Chl-a peaked in winter and spring. These patterns showed a seasonal match between productivity cycles and fish condition indicators. The integration of field-based biometric assessments with remotely sensed oceanographic data reveals clear seasonal patterns in sardine biology and habitat conditions. Higher condition indices were observed in spring and autumn, possibly linked to moderate SST and elevated Chl-a concentrations. The findings underscore the importance of combining geomatics tools and in situ data to monitor fish populations under dynamic environmental conditions. This multidisciplinary approach provides valuable insights for fisheries management and conservation strategies in the southeastern Mediterranean region.