Phenotypic diversity of three populations of the silver catfish, <i>Chrysichthys nigrodigitatus</i> (Lacepède, 1803) in Southwestern, Nigeria

Chrysichthys nigrodigitatus, commonly regarded as the silver catfish, is a highly prized and valued food fish with extensive distribution across African waters. Herein, C. nigrodigitatus was studied for its phenotypic diversity in three different waterbodies: Asejire Reservoir, Epe Lagoon, and Igbokoda River, using their morphological features. Fifty samples of C. nigrodigitatus were collected from each water body, totaling 150 specimens. Thirty morphometric traits and four meristic body counts were recorded on each fish using standard tools. The morphometric measurements were normalized to fish size to eliminate any size-related bias using percentage standard length (SL) and further transformed to common logarithms. Size-corrected data were subjected to One-way analysis of variance (ANOVA) using IBM SPSS 26 and Multivariate analyses (Principal Component Analysis and Cluster analysis) on PAST software. ANOVA showed significant differences (p<0.05) within and between groups of 18 out of the 33 morphological parameters of C. nigrodigitatus examined. Principal Component Analysis (PCA) and Cluster analysis revealed overlapping data between Chrysichthys nigrodigitatus populations from Asejire reservoir and Epe Lagoon, whereas Igbokoda River population formed a distinct cluster. The result suggests that the Igbokoda River population of C. nigrodigitatus is morphologically different from the other two populations (Asejire reservoir, and Epe lagoon) and thus can be regarded as a phenotypically separable population.