Fishes of the Lower Lulua River (Kasai Basin, Central Africa): A Continental Hotspot of Ichthyofaunal Diversity under Threat

Abstract

The ichthyofauna of the Lulua River, a large right bank tributary of the Kasai River in central Africa, is among the most poorly documented in the Kasai ecoregion. To remedy this lack of knowledge, sampling was carried out between 2007 and 2014 along the main channel and in many tributaries. A total of 201 species distributed in 81 genera, 24 families, and 12 orders are reported from the lower reaches of the Lulua. The species richness reported in this study represents a substantially improved documentation of the Lulua ichthyofauna (historically estimated at only 79 species). Here, 129 species are recorded for the first time, bringing the total number of known species to 208. Among these, five have recently been described: Raiamas brachyrhabdotos Katemo Manda, Snoeks, Choca Manda, and Vreven 2018, Distichodus kasaiensis Moelants, Snoeks, and Vreven, 2018, Distichodus polli Abwe, Snoeks, Choca Manda, and Vreven 2019, Epiplatys atractus Van Der Zee, Mbimbi, and Sonnenberg 2013, and Hypsopanchax stiassnyae Van Der Zee, Sonnenberg, and Mbimbi 2015; numerous additional taxa are currently under investigation. Recognized here as a continental hotspot of ichthyofaunal diversity, the Lulua is under extreme threat from exploitation of forest products for building materials, deforestation for shifting agriculture and charcoal exploitation, destructive fishing practices, and mining, all of which are rapidly increasing in the watershed. The present study provides baseline documentation for use in conservation planning and future developmental projects in the Kasai ecoregion in general and Lulua River basin in particular.

Evolutionary convergence in body shape obscures taxonomic diversity in species of the African Labeo forskalii group: Case study of L. parvus Boulenger 1902 and L. ogunensis Boulenger 1910

“…Clearly, the conservation status of each of these is likely to be of much higher concern than is currently recognized. The importance of this finding is underscored by the fact that commercial and artisanal fishing pressures are rapidly increasing throughout the continent due to demographic growth, poverty and food insecurity (Chan et al ., 2021; Mbimbi et al ., 2021; Obiero et al ., 2019). In east Africa, for example, populations of L. parvus sl have been assessed as endangered (Hanssens, 2010).…”

Description of Two New Labeo (Labeoninae; Cyprinidae) Endemic to the Lulua River in the Democratic Republic of Congo (Kasai Ecoregion); a Hotspot of Fish Diversity in the Congo Basin

“…A recent study (Mbimbi et al, 2021) has highlighted the Lulua River, a large right-bank tributary of the Kasai River (fig. 1), as harboring one of the most species-rich fish communities within the entire Congo basin.…”

“…1), as harboring one of the most species-rich fish communities within the entire Congo basin. The Lulua basin is characterized by high geomorphological and hydrological complexity (Roberts et al, 2015) resulting in a wide range of disjunct habitats including numerous rapids and falls, pools, floodplains, and perennial and permanent swamps located within a dense river network of some 71,400 km 2 (Mbimbi et al, 2021). The Lulua ichthyofauna is rich in cyprinids, and most notable is the cooccurence in the basin of an estimated 14 Labeo species (Mbimbi et al, 2021: table A2), rendering the river a potential hotspot of diversity for Labeo within the entire Congo basin.…”

“…The Lulua basin is characterized by high geomorphological and hydrological complexity (Roberts et al, 2015) resulting in a wide range of disjunct habitats including numerous rapids and falls, pools, floodplains, and perennial and permanent swamps located within a dense river network of some 71,400 km 2 (Mbimbi et al, 2021). The Lulua ichthyofauna is rich in cyprinids, and most notable is the cooccurence in the basin of an estimated 14 Labeo species (Mbimbi et al, 2021: table A2), rendering the river a potential hotspot of diversity for Labeo within the entire Congo basin. In a study of cryptic diversity within the L. forskalii group incorporating both morphological and molecular data, Liyandja et al (2022) addressed some taxonomic issues highlighted by Mbimbi et al (2021) but also recognized a number of undescribed lineages of Labeo represented among specimens from the Lulua basin and across central Africa.…”

“…The Lulua ichthyofauna is rich in cyprinids, and most notable is the cooccurence in the basin of an estimated 14 Labeo species (Mbimbi et al, 2021: table A2), rendering the river a potential hotspot of diversity for Labeo within the entire Congo basin. In a study of cryptic diversity within the L. forskalii group incorporating both morphological and molecular data, Liyandja et al (2022) addressed some taxonomic issues highlighted by Mbimbi et al (2021) but also recognized a number of undescribed lineages of Labeo represented among specimens from the Lulua basin and across central Africa. Despite the morphology-based revisionary works of Tshibwabwa (1997) and Reid (1985), the taxonomy and species limits of many of these Labeo remain problematical (Van Steenberge et al, 2016), and an integrative approach is necessary for better taxonomic resolution.…”