diversity Article Fishes of the Lower Lulua River (Kasai Basin, Central Africa): A Continental Hotspot of Ichthyofaunal Diversity under Threat José J. Mbimbi Mayi Munene 1 , Melanie L. J. Stiassny 2,3 , Raoul J. C. Monsembula Iyaba 1 and Tobit L. D. Liyandja 1,2,3, * 1 2 3 * Département de Biologie, Faculté des Sciences, Université de Kinshasa, Kinshasa 01033, Democratic Republic of the Congo; jjmbimbishambuyi@gmail.com (J.J.M.M.M.); raoul.monsembula@greenpeace.org (R.J.C.M.I.) Richard Gilder Graduate School, American Museum of Natural History, New York, NY 10024, USA; mljs@amnh.org Department of Ichthyology, Division of Vertebrate Zoology, American Museum of Natural History, New York, NY 10024, USA Correspondence: tliyandja@amnh.org or liyandja@gmail.com; Tel.: +1-212496-3667 Academic Editor: Simon Blanchet 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. Received: 3 July 2021 Keywords: fish diversity; Congo Basin; Kasai River; biogeography; taxonomy; threatened species



 Citation: Mbimbi Mayi Munene, J.J.; Stiassny, M.L.J.; Monsembula Iyaba, R.J.C.; Liyandja, T.L.D. Fishes of the Lower Lulua River (Kasai Basin, Central Africa): A Continental Hotspot of Ichthyofaunal Diversity under Threat. Diversity 2021, 13, 341. https:// doi.org/10.3390/d13080341 Accepted: 22 July 2021 Published: 26 July 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1. Introduction The Congo Basin (CB) comprises an immense hydrographic network with a wide variety of habitats hosting an extremely diverse fish community currently estimated at 1270 species, of which over 75% are considered basin endemics [1–3]. Second only to the Amazon in terms of volume, the CB drains an area of about 3.7 million km2 of Central Africa [4,5], and its location on both sides of the Equator results in the Congo River (CR) discharging an almost constant volume of 1308 km3 [6] of freshwater into the Atlantic Ocean (AO). From its source in the savanna highlands of the Lualaba and Haut-Katanga provinces in southeastern Democratic Republic of the Congo (DRC) to its mouth in the western Kongo Central province, the main channel of the CR flows through 4374 km [5] generating a high diversity of macro- and microhabitats including falls, rapids, swamps, pools, floodplains, flooded forests, lakes, deep rocky substrates, and a short estuarine reach. Along its journey to the AO, in the western basin, the CR is joined by large tributaries such as the Lulonga, Ruki, Ubangi, Sangha, Alima, Lefini, Kwa-Kasai, N’sele, and Inkisi Diversity 2021, 13, 341. https://doi.org/10.3390/d13080341 https://www.mdpi.com/journal/diversity Diversity 2021, 13, 341 2 of 28 that greatly increase its hydrographic and habitat complexity. The alternation of macroand microhabitats creates perfect conditions for isolation of fish populations that may accelerate the processes of speciation even at remarkably small geographic scales [7,8]. Despite such high levels of species richness and endemism, it is recognized that several areas of the CB remain underexplored [9], and their respective ichthyofauna are poorly documented [10]. Therefore, the number of fish species currently reported from the CB is certainly underestimated and fails to capture the true ichthyofaunal diversity in the basin. Historically, ichthyological exploration of the CB dates to the late 19th century [11] but is characterized by unequal sampling across the basin [12]. Paugy [11] reported that one of the earliest fish collecting efforts in the CB was that of N.E. Ballay between 1882 and 1885. Later numerous expeditions, such as those of P.S. de Brazza (1883–1886), M.A. Greshoff and M.P. Delhez (1899), and H. Lang and J.P. Chapin (1907–1915), have contributed to large collections of specimens housed in the Muséum National d’Histoire Naturelle (MNHN), Paris, the Africa Museum (MRAC), Tervuren, the American Museum of Natural History (AMNH), New York, and the Natural History Museum (NHMUK), London. Many of those collections formed the basis for G.A. Boulenger’s influential work on the fish fauna of the CB [13]. From 1929 through the early 1980s, several other studies (e.g., [14–22]) further documented the ichthyofauna of the CB. However, most collecting efforts were undertaken in the CR main channel, some associated lakes, and a few easily accessible tributaries, leaving several major tributaries and sub-tributaries virtually unexplored. This situation has made it very difficult for the scientific community to estimate with precision the true ichthyofaunal diversity of the CB. To improve this situation, the last decade has seen increasing efforts to explore and document under-sampled affluent tributaries of the CR (e.g., [23–31]). However, parts of the CB, particularly those of the Kasai ecoregion, in addition to being seriously impacted by ongoing deforestation and mining activities, remain poorly known [10]. The Kasai ecoregion [32], composed of the Kasai River (KR) and its main tributaries (Kwango, Kwilu, Loange, Lulua, and Sankuru), is one of the largest ecoregions of the CB and, likely due to the presence of numerous rapids and falls that restrict fish movement, is estimated to have a high level of endemism [3]. However, as already noted, this ecoregion remains underexplored, and the occurrence and distribution of many fish species remain uncertain. The lack of documentation for many tributaries and sub-tributaries of the KR constitutes a major deficit in our knowledge of fish biodiversity of CB. An accurate accounting of species diversity is, therefore, of central importance for data-based conservation and sustainable development efforts. As such, species discovery and description remain fundamental tasks for advancing biodiversity studies in poorly documented regions such as the central CB where considerable diversity remains to be documented [33,34]. This study was carried out as part of the Congo Project initiated by the American Museum of Natural History (AMNH), in partnership with the University of Kinshasa (Democratic Republic of Congo) and the University of Marien Ngouabi (Republic of Congo), to assess ichthyofaunal diversity in the middle and lower reaches of the CRiver. Here, we provide an inventory of fish species of the lower reaches of the LR, the distributions of these species across that portion of the river and the KR, and the anthropogenic activities that constitute the main threats to that ichthyofauna and the ecological integrity of the basin. 2. Materials and Methods 2.1. Study Area The LR catchment covers a surface area of about ca. 71,400 km2 and extends between 4.764◦ and 11.111◦ S and between 21.111◦ and 24.119◦ E. The river originates in the Lualaba Province in the southeast of the Democratic Republic of Congo near the Angolan border at an elevation of about 1200 m asl [35], and it gradually descends the Katanga plateau (a northward extension of the Kalahari plateau) crossing the Central Kasai Province to merge with the main channel of the Kasai River at about 58 km downstream of the city of Luebo Diversity 2021, 13, 341 3 of 28 in the Kasai Province. From its headwaters, near the boundaries of the Upper Zambezi and Lualaba ecoregions (Figure 1), to its confluence (at about 386 m asl) with the KR, the Lulua flows over a distance of 1256 km, characterized by high geomorphological complexity [36], resulting in extensive habitat heterogeneity along its main channel including numerous rapids, pools, small and large tributaries, large floodplains, and perennial and permanent swamps [37,38]. The numerous rapids divide the main channel of the LR into several alternating sections of low (muddy and deep) and fast current (rocky and shallow). Figure 1. Map of the Lulua River showing the location of the Lulua catchment in the Kasai ecoregion of the Congo Basin and neighboring ecoregions. The red rectangle indicates the part of the lower LR where this study was conducted. The LR is under a tropical savanna climate characterized by two main seasons: a longer wet season (from October to early May) and a shorter dry season from (mid-May to mid-September). The basin receives an annual rainfall that varies between 1259 and 1750 mm [39]. On the basis of its elevation profile, we divided the LR into three sections: Upper, Middle, and Lower Lulua (Figure 2). The Upper Lulua is about 260 km long, flowing from its source near the Angolan border to Kusununu, about 160 km upstream of the city of Sandoa (Sanduwa), where a significant expansion, from about 200 m to over 1000 m, of the river’s floodplain is noted. Following the classification of McManamay and Derolph [40], that section of the river has a low stream gradient with an average of 2.19 m/km (0.22%). With a length of about 660 km, the Middle Lulua is the longest section of the river and stretches from that first expansion of the floodplain to the Mbumba rapids (just upstream Diversity 2021, 13, 341 4 of 28 of Mwana Nanga at about 336 km from the Lulua outflow into the Kasai) marking the beginning of a long series of rapids. The Middle Lulua is characterized by a very low stream gradient with an average of 0.215 m/km (0.022%). From the Mbumba rapids, the river flows again in a low-gradient zone, marking the beginning of the Lower Lulua, before flowing through a very low stream gradient as it joins the Kasai. That stretch of the river is about 336 km long and can be divided into two subsections. The first subsection is about 200 km long starting from the Mbumba rapids to the vicinity of Muebela and has an average stream gradient of 1.62 m/km (0.162%), with several rapids and localized braiding of the channel. The last 136 km of the LR, which constitutes the second subsection of the Lower Lulua and its estuary, is characterized by a flattening of stream gradient with an average of 0.188 m/km (0.0188%). In this stretch, the LR is joined by its largest and longest tributary, the Kaluebo or Luebo River. Figure 2. Longitudinal profile of the Lulua River and its subdivision into three sections based on the channel slope gradient. Notes on Collection Sites A total of 43 sites were sampled along the lower reaches of the LR including 13 main channel sites, 20 tributaries, and 10 sub-tributaries, as reported in Table A1 and Figure 3. Most main channel sites are in areas of river braiding and rapids (Figure A1), except sites 1 (Luebo), 3 (Nsanga Nyembo), and 9 (Ntumba). Typically, the sampled sites are characterized by shallow habitats with a rocky substrate and fringing sandy beaches. The river flow in these sections is very rapid, generating numerous cascades, rapids, and waterfalls, and vegetal cover is predominately forest islands and woody riparian savannas. Water pH is slightly acidic with an average of 6.65 but can drop to 5.5 (at Dijiba, Site 6). However, a basic pH of 8 was recorded at Site 12 (Kabeya Nsaka) during the dry season. Collecting sites located on tributaries and sub-tributaries are more diverse, ranging from large channels of 35–63 m width (Kaluebo, Miao, and Moyo Rivers) to small creeks of less than 5 m width (Kasonga, Nkalala, and Tukomba Creeks). The pH in these tributaries is generally slightly acidic but varies from 5.5 (Luyenga River) to 7.1 (Kapelekese River). The substrate is also highly diverse, alternating among rocky, muddy, sandy, and leaf covered depending on location along channels (Figure A2). Diversity 2021, 13, 341 5 of 28 Figure 3. Map of the LR sampling sites: (A) green circles, main channel sites; (B) red circles, tributary and sub-tributary sites. 2.2. Ichthyofauna Sampling A total of six field expeditions, each a month long, were undertaken between 2007 and 2014: the first, during the rainy season in December 2007; the second, at the beginning of the dry season in June 2008; the third, during the rainy season in February 2010; the fourth, during the dry season in July 2010; the fifth, at the end of the dry and the beginning of rainy season in September 2011; the sixth, in September 2014. At each site, a stretch of 100 m was defined, and standard fishing techniques were employed [41]. Depending on habitat and conditions, these techniques included dip nets, cast nets, monofilament gill nets, seine nets, and some local fishing gears (Figure A3). In isolated stretches of the main channel and some tributaries, with permission, the controlled use of the isoflavone ichthyocide rotenone, was employed to sample species not readily captured using other methods [42]. Fishes were euthanized, with MS222, prior to tissue sampling and body preservation in accordance with recommended guidelines for the use of fishes in research [43,44]. Most voucher specimens are housed in the Department of Ichthyology at the American Museum of Natural History (AMNH), and associated data are accessible at https: //emu-prod.amnh.org/db/emuwebamnh/index.php. Additional specimens are housed in the Department of Biology at the University of Kinshasa where they serve as teaching materials. Taxonomic nomenclature follows Fricke et al. [45]. In the absence of a comprehensive taxonomic key for the CB ichthyofauna, identification of specimens was determined on the basis of available publications on the ichthyofauna of the Congo provinces and surrounding regions. In addition to Boulenger’s catalog of fishes in the British Museum (Natural History) [46], we consulted several other documents [47–60], and the following internet resources http://www.poissons-afrique.ird.fr/drupal/faunafri, http://www.mormyrids. myspecies.info/en, and https://research.amnh.org/vz/ichthyology/congo/taxoindex.html (all accessed on 1 June 2020). Diversity 2021, 13, 341 6 of 28 2.3. Anthropogenic Activities Anthropogenic activities were surveyed along the LR during our sampling trips. We recorded human activities, both in and outside collecting sites, that likely had direct or indirect impacts on land cover, water quality, fish populations, and hydrology of LR and its tributaries. 3. Results 3.1. Fish Diversity A total of 3825 individuals were collected between 2007 and 2014. Examination of these specimens resulted in the identification of 201 species, belonging to 24 families and 12 orders with their distribution among the main channel and tributaries indicated in columns 1–21 (Table A2). The distribution of species among all sites is provided in Supplementary Table S1. The order Siluriformes, with 49 species, is the most dominant and represents about 24% of all identified species (Figure 4). It is followed by Cypriniformes (20%), Characiformes (19%), Osteoglossiformes (18%), and Cichliformes (6%). These five orders together represent 87% (177 species) of the species diversity currently known from the LR basin. Figure 4. Relative representation of each order in the lower Lulua River. At the family level, the ichthyofauna of the LR is predominated by Cyprinidae, which is the most speciose family with 41 species (20%), followed by Mormyridae with 35 species (17%), Distichodontidae with 19 species (9%), Alestidae with 18 species (8.9%), Mochokidae with 17 species (8%), and Cichlidae with 12 species (6%). The remaining families are less abundant, each with less than 5% (Figure 5). Overall, Cyprinidae, Mormyridae, Distichodontidae, Alestidae, Mochokidae, and Cichlidae account for about 70% of the ichthyofaunal diversity in the lower LR. Diversity 2021, 13, 341 7 of 28 Figure 5. Relative representation of each family in the lower Lulua River. 3.2. Anthropogenic Activities Overall, the economic situation of people in the LR basin is cause for considerable concern. Economic activity is almost entirely based on unsustainable exploitation of natural resources and minerals, and this, along with rapid demographic growth, is placing increasing pressure on ecosystems throughout the LR valley. During our sampling trips, we identified four main categories of human activity with direct or indirect impact on fish communities in LR: (1) activities affecting land cover, (2) water quality, (3) river hydrology, and (4) fish populations (Table 1). The first three categories contribute to habitat loss and degradation, which are the greatest threats to fish communities in central Africa [10], whereas the last category affects fish population equilibrium and contributes to population fragmentation and decline. Table 1. Human activities identified in the LR valley grouped in categories following their impact on the system. Category (1) Land Cover • • • Activities (3) Hydrology (4) Fish Populations Shifting agriculture Settlement Forest exploitation for building materials and charcoal • (2) Water Quality • • Diamond mining Clay mining • • Large- and small-scale damming Diamond mining • • Fisheries Dams Diamond mining Shifting agriculture (Figure A7A,B) is consistently observed along the LR valley (Figure A8) and is a primary source of income and food for numerous households in the area. This activity is the major cause of deforestation and land-cover alteration throughout the valley. Additionally, settlement into the region is very active and characterized by the rapid expansion of preexisting towns and villages, as well as the creation of new villages Diversity 2021, 13, 341 8 of 28 and camps. In the absence of electricity, most households rely on charcoal and firewood for cooking and lighting, further contributing to deforestation. Artisanal alluvial diamond mining (Figure A7E,F) is widespread (Figure A8) and remains the most lucrative activity for local populations throughout the valley. Mines are mostly located along riverbanks, and sometimes whole tributaries are dammed or diverted to mine their beds. Mined materials are directly sifted or washed in the river, releasing large amounts of clay, silt, sand, and gravels. Clay mines (Figure A7C) are generally smaller and provide clay for brick fabrication (Figure A7D) destined for local construction. Currently, the only major hydroelectric project in the LR valley is the Grand Katende hydroelectric dam, with a planned capacity of 64 MW, which is in an advanced planning stage. Fishes play a central role in the regional food supply and are often the only source of animal protein. Fishing activities in the LR are extensive and practiced by men, women, and children primarily for subsistence. Many fishing techniques are used including netting, trapping, damming and dewatering (Figure A7G), long lines, hook and line, and a locally produced vegetal ichthyocide (Figure A7H). Fishing practices are generally unregulated and often destructive, utilizing extremely small mesh-sized nets targeting small fish, as the larger fish are becoming increasingly scarce. 4. Discussion The dominance of Siluriformes, Cypriniformes, Characiformes, Osteoglossiformes, and Cichliformes in the LR reflects a similar composition as found in the entire CB [12,61]. At the family level, the CB ichthyofauna is dominated by Cyprinidae, Mormyridae, Cichlidae, Mochokidae, Alestidae, Distichodontidae, Amphiliidae, and Nothobranchiidae, accounting for 73% of basin-wide diversity [62]. A similar family composition is also found in the LR. We note that the apparent shift in taxonomic dominance in the lower LR is likely due to the fact that representatives of the Siluriformes are distributed among seven families, while Cypriniformes are represented by members of a single family. When compared to the family composition of the northeastern tributaries of the CR in the Cuvette Centrale ecoregion [26], we noticed the dominance of the same families in both systems. However, the most speciose family is no longer the Cyprinidae but the Mormyridae. Such a shift in dominance suggests that a difference of dominant habitats available in these river networks may be the cause. The rivers of the Cuvette Centrale ecoregion flow through dense tropical forests, with numerous blackwater swamps and small forested streams, likely offering more suitable habitats for mormyrid species than for most cyprinids. While the Mormyridae is also predominant in another river in the Kasai ecoregion, the Kwilu [27], as well as in proximate ecoregions [28,34,63], the dominance of Cyprinidae in the lower Lulua is noteworthy and likely reflects the influence of surrounding savannah and grasslands, and a riparian vegetation restricted in width along its course. Additionally, historical connections between the Upper Lulua with the headwaters of the Upper Zambezi ecoregion (see below), with its high number of cyprinid species, may contribute to the large number of cyprinids collected in the present study. These factors, combined with the presence of some characteristic and endemic species, suggest that the LR basin may represent a distinctive ecoregion within the CB; however, additional collecting within the basin is needed before definitive conclusions can be reached. While the family composition of the LR is similar to that of the CB as a whole, species composition indicates some affinities with the Upper Zambezi ecoregion to the south of the basin (Figure 1). Indeed, species such as Pollimyrus castelnaui (Boulenger 1911) (Figure A4E), Enteromius brevidorsalis Boulenger 1915 (Figure A5D), Enteromius thamalakanensis Fowler 1935 (Figure A4B), Enteromius radiatus Peters 1853, Clypeobarbus bellcrossi (Jubb 1965), Parauchenoglanis ngamensis (Boulenger 1911), Hypsopanchax jubbi Poll and Lambert 1965 (Figure A5H), Coptodon rendalli (Boulenger 1897) (Figure A5A), Tilapia sparrmanii Smith 1840, Pseudocrenilabrus philander (Weber 1897) (Figure A5B), Pharyngochromis acuticeps (Steindachner 1866), and Ctenopoma multispine Peters 1844, present in the LR, have Diversity 2021, 13, 341 9 of 28 also been reported from the Upper Zambezi system [25,50,62]. Such affinities with the Upper Zambezi can be explained by the existence of intermittent connections between the headwaters of the two systems during their geological evolution and currently in times of extreme humidity [25,64–67]. From a taxonomic point of view, the lower LR is characterized by a remarkably rich and diversified ichthyofauna. In addition to the 201 fish species inventoried in this study, seven species reported by [14,47,68–70], but not observed during our study, need to be added to the list. These species are Petrocephalus simus Sauvage 1879, Brachypetersius cadwaladeri (Fowler 1930), Clarias dumerilii Steindachner 1866, Synodontis depauwi Boulenger 1899, Tetracamphilius pectinatus Roberts 2003, Trachyglanis intermedius Pellegrin 1912, and Lacustricola katangae (Boulenger 1912). It is likely that these species are rare, are very localized, or occupy specialized habitats and were able to escape capture during our campaigns. Adding these seven species, the total number of species known from the LR basin reaches 208 species. This number will very likely be exceeded in the coming years as we intensively sample more habitats in unexplored areas of the basin, particularly the Middle and the Upper LR. Indeed, of the 1256 km of the main channel, only a 200 km stretch was intensively prospected within the framework of this study. Thus, the present results suggest that the Lulua catchment harbors an extraordinarily high number of fish species in comparison to other CR tributaries, such as the Inkisi River basin where 61 fish species have been reported [31], the Lefini River basin where 140 fish species have been inventoried [30], the N’sele River with 148 fish species [28], the Kwilu River with 150 species [27], the Luilaka and Salonga Rivers, both tributaries of the Ruki River, in the Salonga National Park where 152 species have been inventoried [29], and the Lindi River where 187 fish species have been reported [26]. Overall, only the Itimbiri (232 species) and Aruwimi (246 species) Rivers, in the Cuvette Centrale ecoregion, have been reported to harbor a higher number of species [26] than that reported in the present study. These differences could, of course, be due to many factors including the size of each river catchment, the diversity of habitats, and their respective productivity, to which we can add sampling techniques, effort, and gear used in different studies. Furthermore, according to Worm and Duffy [71], there is a reciprocal influence among the productivity of an ecosystem, its stability, and its biodiversity; thus, the most productive ecosystems would have high diversities. It should be noted that about 14.4% (29 species) of the species reported in the lower LR were exclusively collected in tributaries and have yet to be found in the main channel (species in bold type in Table A2). Tributaries share an additional 83 species with the main channel bringing the total number of species collected in tributaries to 112 (55.7% of the lower LR fish diversity). This suggests that the LR tributaries harbor a significant proportion of species in the system. It is likely that the real proportion of species finding shelter in tributaries is considerably higher as our investigation was halted due to insecurity in the Kasai provinces, and we undoubtedly did not capture the entire species richness of certain tributaries and sub-tributaries since only a single campaign was undertaken in localities outside of the main channel. Furthermore, several tributaries of the lower LR were not surveyed at all. Nonetheless, the main channel harbors the highest number of species and provides shelter to about 85% (172 species) of the basin’s ichthyofauna. Among species reported in this study, five (Epiplatys atractus Van Der Zee, Mbimbi, and Sonnenberg 2013 (Figure A6E), Hypsopanchax stiassnyae Van Der Zee, Sonnenberg, and Mbimbi 2015 (Figure A6G), Distichodus kasaiensis Moelants, Snoeks, and Vreven, 2018, Raiamas brachyrhabdotos Katemo Manda, Snoeks, Choca Manda, and Vreven 2018, and Distichodus polli Abwe, Snoeks, Choca Manda, and Vreven 2019 (Figure A6H)) have recently been described. The first two are endemic to the Lulua basin while the remainder are more widely distributed. Furthermore, eight putatively new species have been identified, namely, Chiloglanis sp. “Lulua”, Tetracamphilus sp. “Lulua”, Epiplatys sp. “pale” Van Der Zee, Mbimbi, and Sonnenberg (in prep) (Figure A6C), Lacustriola sp., Micropanchax sp. (Figure A6H), Enteromius sp. “purple stripe” (Figure A4C), Labeo cf. lukulae “Lulua” Liyandja (in prep), and Labeo sp. nov. Liyandja (in prep). The descriptions of some of these Diversity 2021, 13, 341 10 of 28 are currently underway while others need more investigation to be confirmed as new. In addition, some taxa, such as Chelaethiops luluae, Chrysichthys cf. duttoni, Garra cf. congoensis, and Ctenochromis luluae (Figure A6B), require further taxonomic attention. The species richness reported in this study represents a substantial improvement over the documentation of the LR ¶ichthyofauna historically estimated at 79 species [14,47,68–70]. In columns 22 and 23 of Table A2, distribution data culled from published IUNC assessment of the status and distribution of central African fishes [72], the Kwilu River [27,73], the freshwater fishes of Angola [25,49], and FishBase [62] were used to investigate which of the species reported in this study have previously been recorded as present in the LR basin and/or the Kasai ecoregion as a whole. We found that 129 of the species reported here have not previously been recorded in the LR (Table A2, column 22). Representatives of families such as Malapteruridae, Tetraodontidae, Bagridae, Kneriidae, Clupeidae, Pantodontidae, and Notopteridae have not previously been reported from the LR, and 32 species reported here were previously unrecorded from the Kasai ecoregion (Table A2, column 23). Adding these species to the list of 367 species compiled from existing publications and databases [25,27,60,62,72–75] brings the total number of species currently known from the Kasai ecoregion to 399. On the basis of this assessment, the Kasai ecoregion occupies the first position, in terms of species richness, in the entire CB (exclusive of Lake Tanganyika). It is followed by the Cuvette Centrale ecoregion with 360 species [26,29], the Lower Congo rapids and Lower Congo ecoregions with a combined 328 species [76], and Pool Malebo estimated at 316 species [3]. However, a total of 399 species for the Kasai ecoregion needs further investigation as some of the species in these lists, such as Labeo ansorgii, Labeo cylindricus, and Labeo annectens, may have far more restricted distributions than currently indicated, and it is highly likely that additional species will be documented in the Middle and Upper Lulua (personal observation). Additionally, it has become clear that molecular analyses are needed throughout the entire basin to ensure that species are not under-split due to rampant cryptic speciation [77–79] or over-split due to morphological plasticity (Liyandja, in prep.). The highly diversified ichthyofauna of the lower LR and that of the entire basin is threatened by a combination of exploitation of forest products for building materials, deforestation for shifting agriculture and charcoal production, destructive fishing practices, and mining (particularly for diamonds), as presented in the results. According to Nguimalet [80], alluvial diamond mining is responsible for regressive and lateral erosion resulting in a complete restructuring of river geomorphology in the Central African Republic. Such changes lead to significant habitat loss and, consequently, to fish population fragmentation and/or decline. In addition to geomorphological modifications, water quality is impacted by clay, silt, and other materials released into the water, by sifting or washing operations during diamond mining, which further increase turbidity and conductivity. Soil erosion caused by deforestation and increase in runoff also contribute to the modification of water quality by carrying more materials (sediment runoff) into the water. This excess of particulate matter in suspension affects fish physiology in numerous ways, including suffocation by clogging their gills [81]. As human populations increase, each of these activities will continue to intensify, and threats are expected to worsen throughout the region. Additionally, intensification of mining and dam construction projected to support the planned Congolese Government developmental programs is underway. A prime example is the Grand Katende hydroelectric dam which is now in an advanced planning stage (https://www.afrik21.africa/en/drc-kinshasa-to-restart-work-on-the-katendehydroelectric-dam-64-mw; accessed on 20 June 2021). If completed, the Katende dam will inundate the lower LR where the present study has been carried out, and it will undoubtedly lead to major habitat degradation and likely the extirpation of many fish species [82], numerous of which are of central importance to the fisheries of the region. Subsistence fisheries in the LR valley are not monitored, and no data on the number of fish produced from these activities are available to allow an accurate assessment of their impact on the fish communities. However, according to observations made on the field and the types of Diversity 2021, 13, 341 11 of 28 fishing gear and techniques used by fishers, we can hypothesize that fish resources in the LR valley are under very high pressure and possibly already overexploited. Some of these techniques affect movements of migratory species (Labeo spp., Labeobarbus spp.) and have an impact on their reproduction cycle. Additionally, the repetitive use of locally produced organic ichthyocides, such as Tephrosia spp., have a drastic impact on fish communities. They are already known to be responsible for the decline in species richness and abundance in tropical streams [83]. Among identified species, only one, Teleogramma monogramma, has been evaluated as vulnerable by the IUCN Red list of threatened species [84] in Central Africa. According to Stiassny et al. [10], a congener, Teleogramma brichardi, is critically endangered because of urbanization around its restricted range near Kinshasa. The populations of T. monogramma reported here have only been collected near the City of Kananga and at the Katende site, suggesting that this species may be at higher risk than assessed by the IUCN. Twentyseven (13.4%) species reported in this study have not been evaluated, and 18 (9%) have been reported as data-deficient by the IUCN. Some of these species such as Hypsopanchax stiassnyae, Amphilius maesii, Nannocharax uniocellatus, and Clypeobarbus mediosquamatus appear to have highly localized distributions along the lower Lulua, suggesting that a reevaluation of their conservation status is urgently needed. The remaining species (77%) have been evaluated as of least concern in Central Africa. However, given the intensity of human activities in the LR valley, there is clearly a strong imperative to carry out local evaluation of the conservation status of the LR species. 5. Conclusions The ichthyofauna of the lower Lulua River is continentally outstanding in terms of fish diversity, and the entire Lulua basin may constitute one of the most species-rich fish communities of the CB. Such an elevated level of fish diversity is likely a result of the basin’s extensive habitat diversity ranging from numerous rapids, falls, pools, small and large tributaries, large floodplains, and perennial and permanent swamps, in addition to its location at the intersection of the Kasai and Lualaba ecoregions. Additionally, its shared headwaters with the Upper Zambezi ecoregion have likely also contributed to the high diversity of its ichthyofauna. The present study, which reports more than 200 fish species in the lower LR, represents a baseline documentation that can be used in conservation and future development projects in the Kasai ecoregion in general and in the LR in particular. In the long term, the outcomes of this study are intended as a starting point for monitoring and protecting the biodiversity of the entire basin. Further investigations are necessary to capture the true fish diversity of this exceptional river catchment, and such knowledge will also contribute to a better understanding of the specific composition and biogeographical history of the ichthyofauna of the Kasai basin and that of the CB as a whole. Supplementary Materials: The following are available online at https://www.mdpi.com/article/10 .3390/d13080341/s1: Table S1. Species distribution among sampling sites. Author Contributions: J.J.M.M.M., R.J.C.M.I. and M.L.J.S. contributed to the conceptualization of the study; J.J.M.M.M. and T.L.D.L. collected the data and conducted the investigation; M.L.J.S., J.J.M.M.M. and T.L.D.L. identified the species; J.J.M.M.M. and T.L.D.L. prepared the original draft; R.J.C.M.I. and M.L.J.S. edited and reviewed the draft; T.L.D.L. and J.J.M.M.M. prepared visualizations; M.L.J.S. acquired funding; J.J.M.M.M. and R.J.C.M.I. were in charge of the project administration. All authors have read and agreed to the published version of the manuscript. Funding: Financial support for this project was provided by the AMNH Axelrod Research Curatorship (M.L.J.S.). This research received no external funding. Institutional Review Board Statement: Not applicable. Informed Consent Statement: Not applicable. Data Availability Statement: Associated data are accessible at https://emu-prod.amnh.org/db/ emuwebamnh/index.php. Diversity 2021, 13, 341 12 of 28 Acknowledgments: For assistance with collection and exportation permits, as well as logistical support, we are grateful to Julien Punga Kumanenge, Jean Mukulire Malekani, and Koffi Mulumba, Ministère de l’Agriculture et du Développement Rural, Sécretariat Général de l’Agriculture, Pêche et Elevage, Direction des Pêches, and the Université de Kinshasa, Cabinet du Recteur, Democratic Republic of Congo. Our thanks also to Barbara Brown (in memoriam), Radford Arrindell, Tom Vigliotta, and Chloe Lewis (AMNH) for their help with accessioning and cataloging specimens. We are also grateful to BEBUC, through the Else Kroner-Fresenius-Stiftung foundation, for their financial and moral support to T.L.D.L. Conflicts of Interest: The authors declare no conflict of interest. Appendix A Table A1. Sampling sites: geographic and physicochemical data (* surface temperature). Geographic coordinates are given in decimal degrees with negative latitudes indicating south and positive longitudes indicating east. Site # Locality River Name Latitude (◦ ) Longitude (◦ ) Altitude (m) T (◦ C) * pH Stream Order 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Luebo Beya Nsanga Nyembo Ntumba Shambuyi Dipumu Dijiba Kasende Katende Kampaya Tshimbadi Ntumbu Kabeya Nsaka Mbumba Kakulu Miao Tshilumba Tshilumba Tshilumba Mikalayi Mikalayi Mikalayi Tshiyoyi Tshiyoyi Kantumanga −5.33881 −5.9325 −5.95317 −5.973317 −6.00328 −6.17272 −6.23509 −6.34366 −6.42721 −6.47323 −6.44484 −6.5201 −6.59545 −5.90237 −5.93972 −5.92967 −5.9254 −5.93278 −5.9537 −5.96836 −5.98746 −6.0044 −6.00841 −600,507 21.40929 22.33472 22.34541 22.37388 22.3916 22.45215 22.46443 22.45036 22.41587 22.41857 22.4197 22.43949 22.47788 21.59208 22.22158 22.34352 22.33756 22.34743 22.33714 22.34208 22.33765 22.3906 22.39838 22.52569 377 524 558 518 547 550 606 649 649 680 675 688 725 515 522 520 512 519 529 534 540 545 550 621 28 28 28 30 27 31 30 28 28 25.3 28 26.2 30.3 25 25 28.9 30.5 25.7 30.7 31 24.5 26 31.1 29 7 6 6.4 7 6.4 5.5 6 6.5 6.9 7.1 6.7 8 6.9 6.5 6.5 6.7 6.6 6.5 7.1 6.7 6.6 5.4 6.3 6 25 Kantumanga Lulua Lulua Lulua Lulua Lulua Lulua Lulua Lulua Lulua Lulua Lulua Lulua Lulua Kaluebo Miao Kasonga Tukomba Nkakala Kapelekese Luankadi Mikalayi Nkombua Ngalala Lubi Lukumbi Kumbi −6.00413 22.5266 610 26.8 5.3 26 Kantumanga Musangu −6.00903 22.52278 621 24.7 6 27 28 Bampanya Kamuandu Lunyenga Lunyenga −6.12452 −6.06501 22.52636 22.653 609 648 29 28 5.5 5,8 29 Dijiba Moyo −6.18725 22.48455 562 28 6 30 Kankunku Minkidimbua −6.10658 22.71375 673 25.5 5 31 Kamuandu Tshimayi −6.19377 22.73992 702 29.3 5.4 32 Kamuandu Tshina −6.20182 22.73446 703 24 6 33 Tshimbulu Mitshikiji −650,417 22.7345 760 28 5.4 34 Kazadi Lubondayi −6.5259 22.66918 755 30.6 6 35 Kazadi Mbuyi −6.54477 22.69843 774 28.6 5.8 36 Kazadi Kambambe −6.54879 22.7045 753 29.2 6.2 37 38 39 40 41 42 43 Bunkonde Bunkonde Tshimbawu Kaloba Ntumbu Kaloba Kabeya Nsaka Tshinkelu Kalulua Luna Tshimayi Kabikonyi Mukundulu Munue Mayi −6.27472 −6.27855 −6.35064 −6.43256 −6.44554 −6.45628 −6.51527 22.4909 22.48777 22.51817 22.43643 22.41882 22.44648 22.44906 678 624 722 678 674 699 906 30.5 29.7 27 30 24.3 25.9 28 6.9 6.8 6.5 6.7 6.3 6.6 5.8 Main channel Main channel Main channel Main channel Main channel Main channel Main channel Main channel Main channel Main channel Main channel Main channel Main channel Left bank tributary Left bank tributary Right bank tributary Right bank tributary Right bank tributary Left bank tributary Left bank tributary Left bank tributary Right bank tributary Right bank tributary Right bank tributary Right bank sub-tributary Right bank sub-tributary Right bank tributary Right bank tributary Right bank sub-tributary Right bank sub-tributary Right bank sub-tributary Right bank sub-tributary Right bank sub-tributary Right bank sub-tributary Right bank sub-tributary Right bank sub-tributary Right bank tributary Right bank tributary Right bank tributary Right bank tributary Right bank tributary Right bank tributary Right bank tributary Diversity 2021, 13, 341 13 of 28 Miao Kasongo Tukomba Nkakala Mikalayi Luankudi Kapelekese Nkombua Ngalala Lubi Lunyenga Moyo Kalulua Tshikelu Luna Tshimayi Mukundulu Kabikonyi Munue Mayi Lulua Historically Kasai Basin POLYPTERIFORMES (1) Polytpteridae (1) Polypterus ornatipinnis Boulenger 1902 OSTEOGLOSSIFORMES (37) Pantodontidae (1) Pantodon buchholzi Peters 1876 Notopteridae (1) Xenomystus nigri (Günther 1868) Mormyridae (35) Campylomormyrus alces (Boulenger 1920) Campylomormyrus curvirostris (Boulenger 1898) Campylomormyrus elephas (Boulenger 1898) Campylomormyrus mirus (Boulenger 1898) Campylomormyrus numenius (Boulenger 1898) Campylomormyrus rhynchophorus (Boulenger 1898) Campylomormyrus tamandua (Günther 1868) Campylomormyrus tshokwe (Poll 1967) Cyphomyrus cubangoensis (Pellegrin 1936) Cyphomyrus discorhynchus (Peters 1952) Cyphomyrus psittacus (Boulenger 1897) Gnathonemus petersii (Günther 1862) Hippopotamyrus macroterops (Boulenger 1920) Marcusenius greshoffii (Schilthuis 1891) Marcusenius intermedius Pellegrin 1924 Marcusenius stanleyanus (Boulenger 1897) Mormyrops anguilloides (Linneaus 1758) Mormyrops lineolatusBoulenger 1898 Mormyrops masuianus Boulenger 1898 Mormyrops microstoma Boulenger 1898 Mormyrops sirenoides Boulenger 1898 Mormyrus caballus bumbanus Boulenger 1909 Mormyrus caballus caballus Boulenger 1898 Mormyrus ovis Boulenger 1898 Myomyrus macrops Boulenger 1914 Petrocephalus christyi Boulenger 1920 Petrocephalus cf. schoutedeni Poll 1954 Petrocephalus sauvagii Boulenger 1887 Kaluebo TAXON Lulua Main Channel Table A2. List of species collected at sites in the main channel (lower Lulua) and tributaries. Sub-tributary species are listed in their respective tributaries. Species in bold type were collected only in tributaries. Numbers in parenthesis are species numbers. In columns 22 (Kasai) and 23 (Lulua historically), distribution data culled from [25,27,60,62,72–75] were used to indicate which Lulua species are known to occur in the Kasai ecoregion and which were not reported in the catchment prior to this study. AMNH (Selected Representatives) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 247757, 247472, 268978 X - - - - - - - - - - - - - - - - - - - - X X 253358, 253060 X - - - - - - - - - - - - - - - - - - - - - X 252627, 253052 X - - - - - - - - - - - - - - - - - - - - - X 253224 268982 253131, 268985, 253131 252608 252605, 253223 268986, 251106, 268986 247525, 252609 252609, 253222 268992, 268989, 268992 247444, 253514, 253390 253157 252799, 252612, 253229 251291, 270503 247417, 247446, 243985 252800, 253315, 253319 251125 247507, 252645, 268995 251068 253338, 252821 247471, 251067, 268999 251067, 252730 251133, 251243, 269000 247502, 247405, 253134 269002, 269001, 269002 247518, 247513, 251242 247500, 252819, 253117 252727 251065, 252729, 269016 X X X X X X X X X X X X X X X X X X X X X X X X X - X X - X - - - X X - - X X X - - X - X X - X - - - - - - - - - X X X - X - - X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X Diversity 2021, 13, 341 14 of 28 Kasongo Tukomba Nkakala Mikalayi Luankudi Kapelekese Nkombua Ngalala Lubi Lunyenga Moyo Kalulua Tshikelu Luna Tshimayi Mukundulu Kabikonyi Munue Mayi Lulua Historically AMNH (Selected Representatives) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 253197, 253328 253350, 252822, 252614 252613 247526, 253232, 253339 253130 247436 252615 X X X X X X X - - - X - - - X - X - - X - X - - - X X - - X - - X - - - X - X X X X X X 268979, 253383 252625 247515, 247479 X X X - X - - - - - - - - X - X - - X - - - X - X X 251112, 243627 253217, 253305, 253505 X X - X - - - - - - - - - - X - - - - - - - - X X 253026, 253214 253025, 269220 247422, 269221 252847, 269222 252834, 253204 269226 269095, 251320 253510, 243981 257172 247483, 253189 253194, 253285 253115, 252725 253195, 269089 253125 247817, 253001 247812, 251277 253036 252753 269095, 251320 253364, 251061, 269096 247968, 253454 247971, 247855 252631 X X X X X X X X X X X X X X X X X X X - X X X X X - X X X X X X X X - X - X X X X X X X X - X X - X X X X - X X X X X X - X X - X - X - X X - X X X X X - X - X X X - X - X X X - X X X - - X - X X X X X X X X X - X X X X X X X X X X X X X X X X X X X X X - Kasai Basin Miao Pollimyrus castelnaui (Boulenger 1911) Pollimyrus maculipinnis (Nichols and LaMonte 1934) Pollimyrus nigripinnis (Boulenger 1899) Pollimyrus osborni (Nichols and Griscom 1917) Pollimyrus pulverulentus (Boulenger 1899) Stomatorhinus kununguensis Poll 1945 Stomatorhinus patrizii Vinciguerra 1928 CLUPEIFORMES (3) Clupeidae (3) Microthrissa congica (Regan 1917) Microthrissa royauxi Boulenger 1902 Potamothrissa obtusirostris (Boulenger 1909) GONORYNCHIFORMES (2) Kneriidae (2) Parakneria ladigesi Poll 1967 Parakneria vilhenae Poll 1965 CYPRINIFORMES (41) Cyprinidae (41) Enteromius bifrenatus (Fowler 1935) Enteromius brevidorsalis(Boulenger 1915) Enteromius chiumbeensis (Pellegrin 1936) Enteromius eutaenia (Boulenger 1904) Enteromius fasciolatus (Günther 1868) Enteromius haasianus(David 1936) Enteromius humeralis (Boulenger 1902) Enteromius lineomaculatus (Boulenger 1903) Enteromius cf. luluae (Fowler 1930) Enteromius miolepis (Boulenger 1902) Enteromius paludinosus (Peters 1852) Enteromius radiatus (Peters 1853) Enteromius thamalakanensis (Fowler 1935) Enteromius unitaeniatus (Günther 1866) Enteromius sp “purple stripe” Chelaethiops elongatus Boulenger 1899 Chelaethiops luluae (Nichols and Griscom 1917) Clypeobarbus bellcrossi (Jubb 1965) Clypeobarbus bomokandi (Myers 1924) Clypeobarbus mediosquamatus Poll 1967 Garra cf. congoensis Poll 1959 Labeo cf. chariensis Pellegrin 1904 Labeo cf. cyclorhynchus Boulenger 1899 Labeo cyclorhynchus Boulenger 1899 Kaluebo TAXON Lulua Main Channel Table A2. Cont. Diversity 2021, 13, 341 15 of 28 Kasongo Tukomba Nkakala Mikalayi Luankudi Kapelekese Nkombua Ngalala Lubi Lunyenga Moyo Kalulua Tshikelu Luna Tshimayi Mukundulu Kabikonyi Munue Mayi Lulua Historically AMNH (Selected Representatives) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 251178 X - - - - - - - - - - - - - - - - - - - - - X 247989, 247995 X - - - - - - - - - - - - - - - - - - - - - - 253436, 243606 247850, 269097 247857, 269100 253465, 269104 253465 269111, 247862, 269106 X X X X X X - - - - - - - - - - - - - - - - - X - - X - X X X X X X X 269108 247858, 251173 252632 247498, 269115 247423, 269121 243660, 253039 247516, 269118 253198, 247476, 253277 X X X X X X X X X - X X X - X X X - X - X - - X X - X X X X X - - X X - X X X X X X X X X X X X X X X X X X 252754, 251232, 253153 X - - - - - X - - - - - - - - - - - - - X - X 252624, 269038, 269037 X - - - - - - - - - - - - - - - - - - - - X X 247827, 247828 252719, 253113 252619 251196, 247835 252809, 253016, 253050 X X X X - - - - - - - - X - - X - - - - X - - - - X X X - X - X X X X X X X 247825, 243646, 251289 X - - - - - - - - - - - - - X - - - - - - - X 253111, 252806 X - - - - - - - - - - - - - - - - - X - - X X 247831, 269041 X - - - - - - - - - - - - - - - - - - - - - X 269045, 252721 253161, 243649 253152, 252805 247838, 252622 243637 252784, 251091 247846, 253326 251056, 269051 X X X X X X X X - - - - - - - - - - X - X - X - - - - - X X - - - X X - X X X X X X X X - Kasai Basin Miao Labeo cf. dhonti Boulenger 1919 Labeo fulakariensis Tshibwabwa, Stiassny, and Schelly 2006 Labeo greenii Boulenger 1902 Labeo lineatus Boulenger 1898 Labeo longipinnis Boulenger 1898 Labeo cf. lukulae Boulenger 1902 Labeo lukulae Boulenger 1902 Labeo luluae Fowler, 1930 Cyprinidae (continue) Labeo parvus Boulenger 1902 Labeo sp. nov. (Liyandja in Prep) Labeo altivelis Boulenger 1909 Labeobarbus caudovittatus (Boulenger 1902) Labeobarbus macrolepidotus (Pellegrin 1928) Leptocypris weynsii (Boulenger 1899) Opsaridium boweni (Fowler 1930) Opsaridium ubangiense (Pellegrin 1901) Raiamas branchrhabdotus Katemo, Snoeks, Chocha, and Vreven 2018 CHARACIFORMES (38) Citharinidae (1) Citharinus gibbosus Boulenger 1899 Distichodontidae (19) Distichodus affinis Günther 1873 Distichodus antonii Schilthuis 1891 Distichodus atroventralis Boulenger 1898 Distichodus fasciolatus Boulenger 1898 Distichodus lusosso Schilthuis 1891 Distichodus kasaiensis Moelants, Snoeks, and Vreven 2018 Distichodus maculatus Boulenger 1899 Distichodus polli Abwe, Snoeks, Chocha, and Vreven 2019 Distichodus sexfasciatus Boulenger 1897 Eugnathichthys eetveldii Boulenger 1898 Eugnathichthys macroterolepis Boulenger 1899 Mesoborus crocodilus Pellegrin 1900 Nannocharax brevis Boulenger 1902 Nannocharax elongatus Boulenger 1900 Nannocharax macropterus Pellegrin 1926 Nannocharax procatopus Boulenger 1920 Kaluebo TAXON Lulua Main Channel Table A2. Cont. Diversity 2021, 13, 341 16 of 28 Kasongo Tukomba Nkakala Mikalayi Luankudi Kapelekese Nkombua Ngalala Lubi Lunyenga Moyo Kalulua Tshikelu Luna Tshimayi Mukundulu Kabikonyi Munue Mayi Lulua Historically AMNH (Selected Representatives) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 253326 252717, 252623 253048 X X X - - - - - - - - - - - - - - - - - - - - - X X X 247414, 243618 253147, 252817, 252740 253472 247505, 247440 252749, 253151 251080, 252644 247527, 252649 247774, 247536 252787, 251301 247771, 252823 247777, 247510 243638, 243600 247775, 247506 252594, 253359 269033, 253159 252750, 252598 251208, 248760 252593 X X X X X X X X X X X X X X X X X X - X X X X X - X - - - X X X X X X - - X X X X X X - - X X X X X - X X X - X - X X X - X X X X - - - - X X X X - X - X X - X X X X X X X X X X X - X X X X X X X X X X X X X X X X X X 252642, 247508 X - - - - - - - - - - - - - - - - - - - - - X 253186 253313 252801 252658, 253031 247530, 243989 247473, 253187 243628 252657, 269135 X X X X X X - - X X X - X X X - - - - - X X - X X X - X - X - - - X - - X X - X X X X X X X X X X X X 247495, 253183, 253314 252831 251238, 251305 243604, 269124, 253215 253185 252785 2474745, 253301, 253199 X X X - X X - - - - - - - - - - - X X X X X X - - - X - - - - X X X X X X X X - Kasai Basin Miao Nannocharax taenia Boulenger 1902 Nannocharax uniocellatus (Pellegrin 1926) Phago boulengeri Schilthuis 1891 Alestidae (18) Alestes liebrechtsii Boulenger 1898 Alestes macrophthalmus Günther 1867 Bathyaethiops breuseghemi (Poll 1945) Brachypetersius altus (Boulenger 1899) Brycinus comptus (Roberts and Stewart 1976) Brycinus grandisquamis (Boulenger 1899) Brycinus humilis (Boulenger 1905) Brycinus imberi (Peters 1852) Brycinus kingsleyae (Günther 1896) Brycinus macrolepidotus (Valenciennes 1850) Bryconaethiops boulengeri Pellegrin 1900 Bryconaethiops macrops Boulenger 1920 Bryconaethiops microstoma Günther 1873 Hydrocynus goliath Boulenger 1898 Hydrocynus vittatus Castelnau 1861 Micralestes acutidens (Peters 1852) Micralestes stormsi Boulenger 1902 Phenacogrammus interruptus (Boulenger 1899) SILURIFORMES (49) Bagridae (1) Bagrus ubangensis Boulenger 1902 Clariidae (8) Channallabes apus (Günther 1873) Clariallabes variabilis Pellegrin 1926 Clarias camerunensis Lönnberg 1895 Clarias gariepinus (Burchell 1822) Clarias pachynema Boulenger 1903 Clarias platycephalus Boulenger 1902 Clarias theodorae Weber 1897 Heterobranchus longifilis Valenciennes 1840 Amphiliidae (7) Amphilius maesii Boulenger 1919 Amphilius zairensis Skelton 1986 Belonoglanis tenuis Boulenger 1902 Congoglanis alula (Nichols and Griscom 1917) Phractura scaphyrhynchura (Vaillant 1886) Tetracamphilus sp. “Lulua” Zaireichthys flavomaculatus (Pellegrin 1926) Malapteruridae (3) Kaluebo TAXON Lulua Main Channel Table A2. Cont. Diversity 2021, 13, 341 17 of 28 Kasongo Tukomba Nkakala Mikalayi Luankudi Kapelekese Nkombua Ngalala Lubi Lunyenga Moyo Kalulua Tshikelu Luna Tshimayi Mukundulu Kabikonyi Munue Mayi Lulua Historically AMNH (Selected Representatives) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 247425, 269142 247497, 253122 270504 X X X - - X - - - - - - - - - - - X - - - - - - - - X X - 251288, 269144 243997, 251195 253219, 251283 251245, 253220 251079, 251244 251124 252599 247520 252600 247442, 253123 252602 252601 253345 253308 251062, 247521, 269154 269154 247521, 269158 X X X X X X X X X X X X X X X - X - - - - - - - - - - - X - X X X X X X X - - - - - X X - X X X X X - X X X X X X X X X X X X - 269141, 247431 247765, 253254 251154 X X X - - - - - - - X - - - - - - X - - - - X - - - X - X X - 252634 252744 252635, 253335 247512, 247429 X X X - - - - - X - - - - X - - - - X - - - X X X - X X X X X 252616 247460, 269159 251107 251102, 253154, 253755 252617, 253042 253325 X X X X X X - - - X - - X - - - - - X - - - X - - - - - - - X X X X X X X 247514, 252647 X - X - X - - - - - X - - - X - - - - - - X X Kasai Basin Miao Malapterurus monsembeensis Roberts 2000 Malapterurus microstoma Poll and Gosse 1969 Paradoxoglanis parvus Norris 2002 Mochokidae (17) Atopochilus dybowskii (Vaillant 1892) Chiloglanis micropogon Poll 1952 Chiloglanis sp.”Lulua” Euchilichthys astatodon (Pellegrin 1928) Euchilichthys boulengeri Nichols and La Monte 1934 Synodontis acanthomias Boulenger 1899 Synodontis alberti Schilthuis 1891 Synodontis angelicus Schilthuis 1891 Synodontis congicus Poll 1971 Synodontis greshoffi Schilthuis 1891 Synodontis nigriventris David 1936 Synodontis notatus Vaillant 1893 Synodontis ornatipinnis Boulenger 1899 Synodontis pleurops Boulenger 1897 Synodontis smiti Boulenger 1902 Synodontis soloni Boulenger 1899 Synodontis cf. smiti Boulenger 1902 Claroteidae (7) Auchenoglanis occidentalis (Valenciennes 1840) Chrysichthys cranchii (Leach 1818) Chrysichthys cf. duttoni Boulenger 1905 Claroteidae (continue) Chrysichthys duttoni Boulenger 1905 Chrysichthys longipinnis (Boulenger 1899) Parauchenoglanis ngamensis (Boulenger 1911) Parauchenoglanis punctatus (Boulenger 1902) Schilbeidae (6) Parailia congica Boulenger 1899 Pareutropius debauwi (Boulenger 1900) Schilbe congensis (Leach 1818) Schilbe grenfelli (Boulenger 1900) Schilbe marmoratus Boulenger 1911 Schilbe yangambianus (Poll 1954) SYNBRANCHIFORMES (1) Mastacembelidae (1) Mastacembelus congicus Boulenger 1896 ANABANTIFORMES (8) Anabantidae (6) Kaluebo TAXON Lulua Main Channel Table A2. Cont. Diversity 2021, 13, 341 18 of 28 Kasongo Tukomba Nkakala Mikalayi Luankudi Kapelekese Nkombua Ngalala Lubi Lunyenga Moyo Kalulua Tshikelu Luna Tshimayi Mukundulu Kabikonyi Munue Mayi Lulua Historically AMNH (Selected Representatives) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 25263, 253307, 253045 251312 252591, 253046, 252591 25321, 253342, 253040 253316, 269209, 253316 247474, 252804, 269221 X X X X X X - X X - X X - - - X - X X X - X - X - X - X X - X X X X X X X X X 252590 253306, 253041 X X - - - - - - - - - - - - - - - - - - - - X X 247794, 253420 X - - - - X - - - - - X X X - X - - - - - X X 243980, 269195 269177, 269248 253310 253474, 253061 247842, 253426 253118 243677, 247805, 253182 247805, 251054, 251114 247532, 247819 253416, 253432 243679, 24367, 252639 X X X X X X X X X - X - X X X X X X X - - X X - X - X - - X X - X X X X X X - X - X - X - X X X X X X X X X X X X X X X X X X 253839, 253840 - - - - - - - X - - X X X - - - - - - - - X X X X - Kasai Basin Miao Ctenopoma acutirostre Pellegrin 1899 Ctenopoma gabonense Günther 1896 Ctenopoma kingsleyae Günther 1896 Ctenopoma multispine Peters 1844 Microctenopoma nanum (Günther 1896) Microctenopoma nigricans Norris 1995 Channidae (2) Parachanna insignis (Sauvage 1884) Parachanna obscura (Günther 1861) CICHLIFORMES (12) Cichlidae (12) Coptodon congica (Poll and Thys van den Audenaerde 1960) Coptodon rendalli (Boulenger 1897) Ctenochromis luluae (Fowler 1930) Hemichromis elongatus (Guichenot 1861) Nanochromis nudiceps (Boulenger 1899) Oreochromis niloticus (Linneaus 1758) Pharyngochromis acuticeps (Steindachner 1866) Pseudocrenilabrus philander(Weber 1897) Steatocranus rouxi (Pellegrin 1928) Teleogramma monogramma (Pellegrin 1927) Tilapia sparrmanii Smith 1840 Thoracochromis stigmatogenys (Boulenger 1913) CYPRINODONTIFORMES (8) Nothobranchiidae (3) Epiplatys atractus Van Der Zee, Mbimbi, and Sonnenberg 2013 Nothobranchiidae (continued) Epiplatys multifasciatus (Boulenger 1913) Epiplatys sp. “pale” Van Der Zee, Mbimbi and Sonnenberg (in prep.) Poeciliidae (5) Hypsopanchax jobaerti Poll and Lambert 1965 Hypsopanchax jubbi Poll and Lambert 1965 Hypsopanchax stiassnyaeVan Der Zee, Sonnenberg, and Mbimbi 2015 Lacustriolasp. Micropanchaxsp. TETRAODONTIFORMES (1) Tetraodontidae (1) Tetraodon miurus Boulenger 1902 Kaluebo TAXON Lulua Main Channel Table A2. Cont. 253038, 257173 X - - X - X - - - X - - - - - - - - - - - X X 252449, 252459 - - - X - X - - - - X - - - - - - - - - - - - 252845, 247914 252456 X - - - - - - - - - - - - X - - X - - X - - - - X X 253037, 252441 - - - - - - - - - - - - - X - - - - - - - - X 269241, 269169 269173, 269245 - - - X - - X - - - - X X - - - - - - - - - - - - - 252629 X - - - - - - - - - - - - - - - - - - - - - X Diversity 2021, 13, 341 19 of 28 Appendix B Figure A1. Google Earth projections and biotopes of the collection sites located along the main channel of the LR: (A,B) Luebo (Site 1); (C,D) Katende (Site 8); (E,F) Dipumu (Site 5); (G,H) Beya (Site 2). Diversity 2021, 13, 341 20 of 28 Figure A2. Biotopes of collection sites located in tributaries and sub-tributaries of the LR: (A) Lubi River (Site 24); (B) Luna River (Site 39); (C) Luyenga River (Site 28); (D) Tshimayi River (Site 31); (E) Mikindimbua River (Site 30); (F) Mukundulu River (Site 42); (G) Kabikonyi River (Site 41); (H) Tukomba River (Site 17). Diversity 2021, 13, 341 21 of 28 Figure A3. Fishing techniques: (A) cast net fishing; (B) passive basket fishing (traps) used in lotic habitat; (C) passive basket fishing (traps) in rapids and waterfalls; (D) active basket fishing in shallow stream; (E) active basket fishing in shallow ponds; (F) dip and seine net fishing. Diversity 2021, 13, 341 22 of 28 Figure A4. Selected species reported for the first time in the Kasai ecoregion: (A) Clypeobarbus mediosquamatus; (B) Enteromius thamalakanensis; (C) Enteromius sp. “purple stripe”; (D) Garra cf. congoensis; (E) Pollimyrus castelnaui; (F) Campylomormyrus curvirostris; (G) Cyphomyrus cubangoensis; (H) Distichodus polli. Photographed immediately postmortem, scale = 1 cm. Figure A5. Selected species shared with the Zambezi headwaters: (A) Coptodon rendalli (B) Pseudocrenilabus philander (C) Enteromius brevidorsalis (D) Enteromius chiumbeensis (E) Enteromius paludinosus (F) Enteromius bifrenatus (G) Microctenopoma nigricans (H) Hypsopanchax jubbi. Photographed immediately postmortem, scale = 1 cm. Diversity 2021, 13, 341 23 of 28 Figure A6. Selected endemic species of the LR: (A) Steatocranus rouxi (B) Ctenochromis luluae (C) Opsaridium boweni (D) Labeo luluae (E) Epiplatys atractus (F) Epiplatys sp “pale”. (G) Hypsopanchanx stiassnyae (H) Micropanchax sp. 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