Six populations of morphologically similar Enteromius specimens with a weakly thickened and serrated dorsal spine from the Lowa basin were investigated using an integrative approach including qualitative characters, multivariate morphometrics, and DNA analyses (mtCOI and ncMyh6). These populations are nested within the COI lineage of the E. miolepis species-complex, but differ from all known Enteromius species from the Congo basin, by their dorsal spine morphology, colour pattern, and scale pattern at the dorsal-fin base. In addition, they represent two distinct COI lineages (genetic distance: 5.6–6.1%), with four populations forming a single well-supported lineage described as a new species, Enteromius radari sp. nov. The two remaining populations are sister to the E. miolepis lineage from the Itimbiri. The incongruent position of these two populations in the COI tree may point to past introgressive hybridization events, incomplete lineage sorting, or recent speciation. Analysis of a ncDNA marker (Myh6) did not provide more information due to its slow mutation rate. These results are indicative for introgression or mtDNA capture and provide the first report for such an evolutionary event in Enteromius from the Congo basin. http://zoobank.org/urn:lsid:zoobank.org:pub:D2263E5B-D403-404C-B66C-852215ED100C

In total, 28 of the 29 fish species reported from the Lake Kivu basin occur in the littoral zone of the lake, but information about their structure, occurrence, and the habitats affecting their distribution is largely lacking. The lake’s inshore area is poorly heterogenous, with rock and macrophyte habitats representing the major habitats. The lack of heterogeneity in the habitats is probably an important factor influencing species richness, abundance, and the association between the species and habitats. We evaluated the fish diversity, abundance, and habitat parameters across 14 sites representing the major habitats of the lake, using data collected between April 2018 and October 2019. We calculated Hull and Jaccard indices and applied uni- and multivariate statistical approaches to the collected data. We identified 18 fish species in the lake. In the north, 17 species were found, with high abundance in rocky sites but low abundance in sandy habitats. In the south, 15 species were reported. We identified 12 species in the Ishungu Basin where the site with rock substrate had high abundance and 13 species in the Bukavu Basin with weak species richness and low abundance across degraded sites. Lamprichthys tanganicanus, a non-native species, was abundant in rocky (north) and macrophyte sites (south). Sand, rock, conductivity, depth, dissolved oxygen, and water transparency were significant parameters that could explain the fish distribution in the north while dissolved oxygen, vegetation cover, depth, and conductivity were significant in the south. A monitoring programme of the fish fauna in Lake Kivu is needed.

The upper Malagarazi (uM) Basin is situated in Southeastern Burundi and Northwestern Tanzania, and partially covered by the Malagarazi Nature Reserve (MNR). A checklist of fishes from the uM, in Burundi, is presented based on a literature review, a re-examination of historical collections, and a study of new collections (2013–2022). A total of 74 native species, including 14 endemics and two introduced Oreochromis, distributed over 38 genera and 16 families, are reported. Of the aforementioned species, 60 native (81%) and one introduced are present in the MNR. The most important families in the uM and the MNR are the Cyprinidae (21 versus 17 species, respectively) and Cichlidae (12 versus 11). Other families are represented by less than 10 species in both the uM and the MNR. Furthermore, of the 14 species endemic to the uM (19%), only eight (57%) are reported from the MNR; the others are confined to some non-included affluent rivers. Moreover, eight taxa still await formal description. Finally, as some endemic and native species are not included within the current borders of the MNR, adjustments are proposed and the need for a new protected area is considered.