MORPHOLOGICAL-DIFFERENTIATION OF THE PIKEPERCH STIZOSTEDION-LUCIOPERCA (L) POPULATIONS FROM THE YUGOSLAV PART OF THE DANUBE

In order to analyse the intra- and interpopulation homogeneity/heterog eneity of the pikeperch (Stizostedion lucioperca), the phenotypic vari ability of morphological characters was estimated on the basis of a bi ometric analysis of 31 morphometric and 10 meristic characters in 284 specimens collected at four different sections along the Yugoslav sect or of the Danube, during 1986-1989. An ANCOVA of morphological charact ers, with fish size as a covariate, was performed for analysed samples and between males/females and adults/juveniles respectively. Comparis on was also made with the pikeperch samples from the Dnepr and the Wes t Dvina (Zhukov 1965). The results were tested with a GT2-method for m ultiple unplanned comparison of means, or with a t-test where appropri ate. The differentiation between populations from three geographically distinct and isolated areas (Danube-Dnepr-Dvina) is much greater than between the four samples from the Danube. The results of the variabil ity analysis of morphological characters and known pikeperch habits (f irst of all having in mind the so-called ''homing'' effect - returning to the same spawning place from year to year), suggest that the four samples from the Yugoslav part of the Danube most probably represent f our distinct populations. The presence of reproductive isolation still has to be proved through experimental marking. Since this analysis ta kes into account only the phenotypic variation, it would be necessary to study the genetic differentiation between populations, as well, by biochemical or DNA-sequencing methods.