Comparative Morphology and Morphometric Relationships of Otoliths in Five Carangidae Species from the Gulf of Guinea (Côte d’Ivoire)

Abstract

Aims: To describe sagittal otolith morphology and determine morphometric relationships between otolith dimensions and total body length in five Carangidae species from the Gulf of Guinea (Caranx crysos, Caranx senegallus, Chloroscombrus chrysurus, Trachurus trecae, Trachinotus ovatus). The goal was to provide diagnostic criteria and quantitative references for taxonomy, species identification and fisheries assessment. Study Design: Descriptive and analytical study combining qualitative otolith morphology with linear morphometric modelling. Place and Duration of Study: Port of Abidjan, Côte d’Ivoire. Sampling took place from May to September 2024. Methodology: A total of 160 specimens from five Carangidae species were measured for total length and weight. Sagittal otoliths were extracted, cleaned and examined under stereomicroscope. Otolith length, width and weight were quantified using image-analysis software. Symmetry between right and left otoliths was tested with the Wilcoxon test. Linear regressions assessed relationships between total fish length and otolith parameters. Morphological traits (outline, margins, sulcus pattern, cauda orientation, rostrum development) were described following standard ichthyological guidelines. Results: Length–weight relationships showed strong correlations (r > 0.95; p < 0.001) with variable allometry (0.34 in C. chrysurus to 2.94 in C. senegallus). No significant right–left asymmetry was detected (P > 0.05). Total length correlated strongly with otolith weight (r = 0.81–0.98 ; r² up to 0.96), length (r² up to 0.96) and width (r² up to 0.92). Interspecific differences included robust crenulated otoliths in T. trecae, a pronounced rostrum in C. crysos, a wide ventral cauda in C. senegallus, marked crenulations in C. chrysurus and a rounded ellipsoid shape in T. ovatus. Conclusion: Morphological and morphometric otolith characteristics offer reliable markers for discriminating Carangidae species. Strong otolith–length correlations support their use for size reconstruction and taxonomy. Additional studies integrating microstructure or elemental composition are recommended.