The golden mudsuckers (Labeo spp.) from above and below the Victoria Falls: Sibling species along different invasion routes

Abstract

The colonization of Lake Kariba with species of the Upper Zambezi fauna brought home the fact that only scant knowledge is available concerning the distribution principles prevailing above and below the Victoria Falls . It, therefore, seemed apparent that a study contributing to a better understanding of this was necessary . To this effect fishes were sampled at the edge of this formidable geographical barrier (Balon, 1974b) . When collection and analysis were completed it became clear that the taxonomic status of the large yellow-fish (Barbus marequensis) and the golden mudsuckers (Labeo spp .) had to be resolved first . The question was: are these species upstream and downstream from the Victoria Falls identical or different, and if so to what extent? Labeo annectens was first described from a small tributary of the Campo River near Efulen in Cameroon . It was originally thought to be limited to the Congo River system (Boulenger, 1909 ; Jackson, 1961), however, when recorded from the Upper Zambezi River at Chavuma in 1963 and from the Kafue River at Itumbi in 1964 by BellCross (1965a) it appeared to replace (Jubb, 1964b) the earlier identifications -Labeo cylindricus and L. forskalii (see Jackson, 1961 and 'linyonga' in Jubb, 1964a) -of the golden mudsuckers above the Victoria Falls . L. forskalii was at the same time diagnosed (Bell-Cross, 1965a) as a new species L. lunatus Jubb, 1963 . The identity of L. cylindricus and L. annectens was, however, doubted by Jubb (1967, p . 240) . Nevertheless Bell-Cross and Kaoma (1971) decided that fish previously identified as L. annectens are L. cylindricus . In the Kafue and Middle Zambezi