Variation in the shape and size of the scale of the Tigris bream (Acanthobrama marmid, Heckel, 1843) from the Tigris River, Türkiye attributed to Seasonality, Age and Sex: A geometric morphometric study

Abstract

In this study, the Tigris bream Acanthobrama marmid individuals (44 females and 31 males) were captured from the Tigris River. The scale size (as centroid size) and shape were analyzed separately using 2–dimensional geometric morphometric methods. Procrustes ANOVA revealed significant differences in scales size between sexes, while no difference in shape was observed. Groups based on season and age showed significant differences in both size and shape. Female individuals had larger scale sizes than males, with the scales of the Autumn group being larger than those of the Spring and Summer groups. Scale size also increased with age groups. PCA analysis showed variation in the first five components when examined by age, season, and gender. CVA and DFA results indicated significant differences in shape between different age groups and seasonal groups, but no significant differences between sexes were observed.