Abstract
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.