Morphological differentiation of introduced pikeperch (Sander lucioperca L., 1758) populations in Tunisian freshwaters

Summary In order to evaluate the phenotypic plasticity of introduced pikeperch populations in Tunisia, the intra‐ and interpopulation differentiation was analysed using a biometric approach. Thus, nine meristic counts and 23 morphological measurements were taken from 574 specimens collected from three dams and a hill lake. The univariate (anova) and multivariate analyses (PCA and DFA) showed a low meristic variability between the pikeperch samples and a segregated pikeperch group from the Sidi Salem dam which displayed a high distance between mouth and pectoral fin and a high antedorsal distance. In addition, the Korba hill lake population seemed to have more important values of total length, eye diameter, maximum body height and a higher distance between mouth and operculum than the other populations. However, the most accentuated segregation was found in the Lebna sample where the individuals were characterized by high snout length, body thickness, pectoral fin length, maximum body height and distance between mouth and operculum. This study shows the existence of morphological differentiations between populations derived from a single gene pool that have been isolated in separated sites for several decades although in relatively similar environments.