Body Shape Variations of Tank Goby <i>Glossogobius giuris</i> (Hamilton 1822) in Three Distinct Water Bodies of Central Vietnam

Abstract Tank goby Glossogobius giuris is widely distributed across Vietnamese rivers, estuaries, and lagoons, particularly in the central region where this species plays a pivotal role as a high commercial source for local communities. In this study, we employed landmark-based geometric morphometrics to compare the morphometric variations among three distinct populations of G. giuris inhabiting the Tam Giang Lagoon (Thua Thien Hue Province), Nhat Le Estuary (Quang Binh Province), and Truong Giang River (Quang Nam Province), Vietnam. The analysis, utilizing Permutational Multivariate Analysis of Variance (PERMANOVA) with Mahalanobis distances, revealed significant differences in the body shape among the three populations ( P &lt; 0.001). Specifically, with respect to the lateral side, the highest Mahalanobis distance was observed between specimens from the Tam Giang and Nhat Le, followed by the Tam Giang and Truong Giang River, with the lowest value found between the Nhat Le and Truong Giang. A similar pattern was observed for the dorsal side. Canonical variate analysis (CVA) illustrated three distinct groups with statistical significance in all cases ( P &lt; 0.001) and the confusion matrix showed a high corrected grouping rate of 88.5% for the lateral side and 82.8% for the dorsal side. These findings indicated notable variations in the body shape of G. giuris among the three studied areas. Fish sampled from the Tam Giang Lagoon exhibited a streamlined body shape, while those from the Truong Giang River and Nhat Le Estuary displayed a deeper body profile. The observed morphological differences among these fish populations are likely attributed to phenotypic adaptations driven by environmental factors and habitat distinctions. Importantly, this study marks the first attempt to compare the body shape variations of G. giuris in both freshwater and estuarine environments within central Vietnam, utilizing a landmark-based geometric approach. These findings provide crucial insights for further investigations into the ecological adaptations and evolutionary processes of this fish species.