Analysis of biometric relationships and condition factor of Oreochromis niloticus in the lacustrine ecosystems of Yamoussoukro (Ivory Coast)

The study focused on the size distribution, length–weight relationship, and condition factor of Oreochromis niloticus in several urban and peri-urban lakes of Yamoussoukro. Standard lengths of individuals varied across lakes, ranging from 8.3 to 18.5 cm. Size classes were established according to Sturges’ rule, revealing variable counts between 2 and 38 individuals per class. In all lakes, counts differed significantly between size classes (Kruskal–Wallis tests, p < 0.05), with the largest size classes generally having the fewest individuals and intermediate classes the most. Analyses of the length–weight relationship showed a strong positive correlation (0.87 ≤ R² ≤ 0.95) and no outliers, indicating reliable measurements. Fish growth was isometric in Lake 4 (b = 3) and negatively allometric (b < 3) in the other lakes. The mean condition factor (K) was above 0.5 in all lakes, with no significant differences between sites, suggesting that the fish were generally in good body condition.