Abstract

Introduction The earliest studies on ichthyofauna of the Upper Vistula River were reported by Wałecki ( ), Nowicki ( , ), and Fischer ( ), all of whom noted the occurrence of two gudgeon species: the common gudgeon Gobio gobio (Linnaeus, 1758) and the longbarbel gudgeon Romanogobio uranoscopus (Agassiz, 1833). Nowicki ( ) specified that the latter species is known only from one tributary of the Upper Vistula, the San River. This was questioned by Staff ( ), who concluded that the description provided by Nowicki ( ) better fits the Kessler's or sand gudgeon Romanogobio kesslerii (Dybowski, 1862) than R. uranoscopus . Rolik ( , ) examined several dozen specimens from the San River and concluded that in fact they do belong to R. kesslerii ; the known occurrence of this species in the Vistula River drainage has been restricted to a lone tributary, the San River. In the Department of Ichthyobiology and Fisheries collection of the University of Agriculture in Kraków, E. K. Balon (pers. comm. in Oliva, ) found a single specimen of R. kesslerii labelled as originating from the Raba River, another tributary of the Upper Vistula. However, that information has been attributed to