<p>Morphological variability of round sardinella (<i>Sardinella aurita</i>) was examined along the central Algerian coast during the reproductive period (June–August 2023) to establish contemporary biometric baselines and evaluate phenotypic patterns in a key Mediterranean small pelagic fish. Sixty adult specimens (30 females and 30 males) were analyzed for six meristic and twelve metric characters. Meristic traits exhibited strong uniformity (coefficient of variation &lt; 6.5%) with no significant differences in meristic characters between sexes. Mean vertebral number was 45.13 ± 1.17 (range: 43–47), representing the lowest mean value reported to date for Mediterranean populations relative to historical records. Fin ray counts averaged 16.78 ± 0.96 (dorsal), 16.38 ± 0.98 (anal), and 20.90 ± 1.60 (caudal), remaining consistent with long-term regional values. Metric analyses revealed moderate female-biased size dimorphism, with females attaining greater total length than males (<i>p</i> = 0.03), while analysis of covariance demonstrated no intrinsic shape differentiation between sexes after size correction (<i>p</i> &gt; 0.05). Length–length relationships showed predominantly negative allometry (<Emphasis Type="BoldItalic">b</Emphasis> &lt; 1), indicating differential scaling of body proportions during ontogeny, except for pre-orbital length (<Emphasis Type="BoldItalic">b</Emphasis> = 1.81), reflecting disproportionate visual region development. By integrating contemporary data with historical Mediterranean records, this study highlights vertebral counts as a potential, although indirect, indicator of developmental responses to environmental conditions, amenable to integration into routine fisheries monitoring frameworks.</p>