This research addresses skeletal deformities in two freshwater fish species, namely the common carp, Cyprinus carpio, and Leuciscus vorax (also known as the Tigris asp), sampled from two Iraqi sites: The Euphrates River, Lake Al-Tharthar, and the Tigris River near Al-Zubaydiyah City. High-resolution digital radiography was used to detect skeletal deformities in 40 specimens (20 specimens per species). Five different types of deformities were observed in C. carpio: abdominal rib deformity (13.6% of the deformed specimens), ankylosis (18.8%), caudal fin ray deformity (4.6%), kyphosis (4.6%), and vertebral deformity (4.6%). In L. vorax, three categories were observed: caudal fin skeleton deformity (4.6%), vertebral compression syndrome (40.9%), and vertebral deformities (9.1%). Vertebral compression in L. vorax was particularly notable, with affected specimens exhibiting anteroposterior shortening, reduced fork length to total length ratios (79.3–90.9% versus 98.1% in normal specimens), and decreased vertebral column length to standard length ratios (50.3–56.0% versus 64.6% in normal specimens). Furthermore, the uncompressed samples showed differences in the number of vertebrae (48 compared to 47), possibly indicating a developmental abnormality during embryogenesis. The results establish an important baseline of data for future biomonitoring studies in Iraqi freshwater habitats, as well as a fundamental understanding of skeletal pathology in wild fish populations. This knowledge of skeletal anomalies also enables researchers to distinguish normal from abnormal morphological features, aiding in correctly interpreting fish morphology.
