Background. The zope (blue bream), Abramis ballerus (L., 1758), is a cyprinid fish without economic importance, and its morphology has been poorly known. The monophyly of the genus Abramis is still unclear; therefore any new contribution to the knowledge on the morphology of zope could shed a new light on the phylogeny of this group of fishes. The aim of the present study was to learn and describe meristic- and morphometric futures of zope and to compare the results with published data. Materials and Methods. A total of 40 specimens of the zope, Abramis ballerus, were caught in the middle stretch of the Odra River, near the city of Głogów, western Poland, in October 2002. For each fish, 21 biometric features were measured and selected meristic features (external and internal) were determined. Cephalic sensory canals were studied and their pores were counted. Results. The coefficient of variation for the body proportions of zope from the middle stretch of the Odra River ranged from 3.89% to 19.13% and its principal features were as follows: D III 8–10; A III 34–43; P I 14–18; V II 7–9; l.l. 62–75. It had one row of pharyngeal teeth, most frequently, in 5–5 pattern. The total number of vertebrae ranged from 46 to 48, (mean 47.38). The preoperculo-mandibular canal (CPM) and infraorbital canal (CIO) had the highest number of pores. Conclusion. The presently reported study shows that the sample analysed did not differ significantly from the population of the Dniepr River, although it differed significantly (in body proportions) from those of Lake Dąbie. The majority of values of meristic features did not differ significantly from those found in literature. However, there is still too little comparative material regarding internal meristic features and especially its osteology.
Sturgeon frywere obtained through the artificial spawning of Siberian sturgeon (Acipenser baeri Brandt) and the hybrid of Siberian and Russian sturgeon (Acipenser baeri Brandt x Acipenser gueldenstaedti Brandt). Selected biotechnological factors of the fish were compared and biometric measurements were taken during a 60-day long rearing period in a recirculation system. A higher growth rate was confirmed in the hybrid sturgeon. The average body weight of the hybrid at an age of nine months was 1,078 g, while that of the Siberian sturgeon was 872 g. The hybrid also utilized feed more efficiently. The food conversion rate during the study period was 0.64 for the hybrid and 0.66 for the Siberian sturgeon. The greatest differences in the plastic features of the studied fish were found for those related to the head. The Siberian sturgeon had a longer rostrum (R) and a shorter post-orbital space (op) than did the hybrid. Significant differences were also observed in the numbers of lateral bony plates (Sl), the number of rays in the dorsal fins (D) and the number of rays in the anal fins (A).