Ecological monitoring of fish in the southern sector of the Azerbaijani coast of the Caspian Sea

This study presents the results of marine monitoring conducted in the littoral zone of the Caspian Sea at three distinct sites within the southern Lankaran aquatory: Lankaran, Zud-Ost Goltug, and Nord-Ost Goltug. Genotoxic analysis of blood erythrocytes and histological examination of gill and liver tissues were carried out on captured fish specimens, including goby, Caspian roach, kutum, and anchovy sprat. The genotoxic analysis of erythrocytes revealed abnormalities such as nuclear invaginations, hemoglobin degradation, nuclear displacement, and bean-shaped nuclei. The prevalence of identified pathological cells was up to 4.41%, a level approaching the upper limit of the normal physiological range. Histological examination of the gills showed pathological changes including hyperplasia, curvature, and misalignment of secondary lamellae, adhesions, proliferation of the interlamellar epithelium, the presence of mucoid secretions on the surface of the respiratory lamellae, edema of the secondary lamellae, as well as deformation and fusion of the apical regions of the lamellae. Histopathological analysis of the liver tissue revealed lesions such as dilation of hepatic sinusoids, focal vascular congestion, and clusters of melanomacrophages. The observed genotoxic abnormalities were within the established physiological range. The histological changes in the gills and liver exhibited features consistent with protective and adaptive responses. This research provides essential data for biodiversity conservation strategies in these aquatic ecosystems.