Changes made to the scientific names of southern African freshwater fishes since 2001 are explained and discussed. Adjustments to the phylogeny and classification of the fauna are outlined. Recent systematic studies on cyprinines are discussed and changes to the genera Labeobarbus (expanded concept), Pseudobarbus (expanded concept), and Enteromius are supported. The introduction of the family names Alestidae and Nothobranchiidae is discussed. Adjustments made to the genera Nannocharax, Micropanchax, Tilapia, Coptodon and Mastacembelus are explained. Species name changes for Hepsetus and Zaireichthys are detailed. New species described from the region, or resurrected from synonymy, since 2001 are listed.
Pollution threatens fish health in the eutrophic lakes, Chivero and Manyame, in Zimbabwe. Histopathological tissue alterations of two commonly consumed fish: catfish, Clarias gariepinus, and; tilapia, Oreochromis niloticus, from Lakes Chivero and Manyame were assessed between 2015 and 2016. Seventy-one (71) catfish and 81 tilapia were caught using gill nets, and samples of their gills, liver, kidney and stomach tissue were collected and assessed microscopically for manifestations of disease. Pathologies observed in the gills of tilapia and catfish from both lakes included lamellar fusion, hyperplasia of primary lamellar epithelium and disintegration of secondary lamellar epithelium. Liver histopathology revealed vacuolation, presence of melanomacrophage centres and inflammatory cell infiltration in catfish and vacuolation in tilapia from both lakes. There were no significant differences (Chi-squared-test, p > 0.05) in the frequency of occurrence of some histological lesions in tissues assessed for the unrelated catfish and tilapia in the two lakes. Lamellar fusion in the gills conjoined neighbouring lamellae suggests the presence of parasites. Melanomacrophage centres observed in catfish may reflect metal pollution. Observed lesions in populations from both lakes suggest exposure to similar stressors and high tolerances and adaptation to eutrophic conditions.
Although biomonitoring of freshwater bodies is important in East Africa as a result of increasing environmental threats, the identification guides of benthic macroinvertebrates used to generate data for developing metrics for this purpose are mainly not regionally specific. This casts doubt on the reliability and utility of generated data, given varying macroinvertebrate taxa in biogeographical regions. This review examined literature on freshwater macroinvertebrate studies and focused on the types of identification guides that are in use in East Africa, with a view of developing local ones for the region, to enable reliable and effective data collection and usage. The literature examined included peer-reviewed papers, books, dissertations, and un-refereed reports. Currently, it is mainly macroinvertebrate identification guides from temperate and other regions that are used in East Africa. Therefore, there is a need to develop identification guides that are based on local benthic macroinvertebrate species of East Africa. To achieve this, both lotic and lentic freshwater macroinvertebrates in various localities of East Africa should be collected through standardised protocols, taxonomically characterised and documented. Molecular phylogenetic tools, coupled with creation of a database should be considered to aid species identification of macroinvertebrates and freshwater biomonitoring in East Africa.
This study quantified growth, mortality, and exploitation rate of the black-chinned tilapia (Sarotherodon melanotheron melanotheron) population in Etsir Lagoon, a small brackish waterbody at Abandze (5°11′ N, 1°5′ W) in the Central Region of Ghana for management of the stock. Fish samples were collected monthly between April 2014 and March 2015, and specimens measured 3.9-13.8 cm SL with a mode in the 7.0-7.9 cm length class. Analysis of the length-frequency data of 861 specimens using the ELEFAN method indicated a growth constant (K) of 0.93 yr −1 , and asymptotic length (L ∞ ) of 14.3 cm SL for the population. The short lifespan (t max = 3.2 years) determined for the species and estimated growth parameters suggest stunting in the population, as in other brackish water populations in Ghana. The total mortality (Z), natural mortality (M), and fishing mortality (F) coefficients: 5.09 yr −1 , 2.15 yr -1 and 2.95 yr −1 , respectively, indicate fishing as a major contributor to total mortality. The calculated exploitation rate (E = 0.58) of the population suggests overexploitation of the stock, however, the all-year- round recruitment in the population probably ensures production at levels that compensate for its relatively high exploitation rate.
Sediment grain size and organic matter influences the distribution of macrozoobenthic fauna. These parameters also influence bioavailability and toxicity of contaminants in aquatic systems, because sediment is the sink and source for most contaminants. These sediment parameters therefore potentially confound sediment toxicity results when using inappropriate toxicity test organisms and/or test conditions. Grandidierella lignorum is being developed as a sediment toxicity test organism for South African coastal waters and it is crucial that its preference for sediment grain size and organic matter is determined with the aim of defining test conditions for sediment toxicity tests. G. lignorum were offered a choice of six sediment grades and two types of organic matter of varying concentrations (0-8%) to determine their preference thereof. Very coarse sediment grade and mud were consistently the least selected particle sizes in all experiments. Sediment with low organic matter (<0.5%), was also consistently selected by G. lignorum and this was not influenced by sediment particle size. G. lignorum can therefore be used for the toxicity testing of sediment with a wide grain size variation, although results may be confounded in sediment samples largely comprised of very coarse or muddy sediment.
The Albertine Rift is one of Africa's major biodiversity hotspots. However, the aquatic fauna of its western border in Democratic Republic of Congo (DRC) remains understudied and poorly characterised. Kahuzi-Biega National Park (KBNP) in DRC is a crucial link for biodiversity conservation of this hotspot; however, scientific studies of this rich biodiversity are scarce because of insecurity and harsh field conditions. In the current study, benthic macroinvertebrates communities and some environmental conditions were investigated in 10 rivers in the KBNP. Eighty-four morphospecies, belonging to 47 families and 12 orders, were sampled from 13 sites. The abundance and diversity of taxa within systematic groups varied across the study area. Spatial distribution of systematic groups was also analysed. The high morphospecies richness, characterised by the number of families and Shannon's and Simpson's Diversity Indices, recorded at some sites was probably owing to the diversity of substratum and undisturbed environmental conditions observed in these forested rivers. Conversely, some sites presented lower species richness, possibly because of unfavourable natural conditions.
This study investigated the temporal changes in the sex specific ingestion rates of the recently described calanoid copepod, Lovenula raynerae, which numerically and by biomass dominates the plankton community in ephemeral ponds in the Eastern Cape province of South Africa. Ingestion rates of the copepod were investigated on two occasions, one week after emergence and two weeks thereafter, employing the gut fluorescent technique. Results of the study indicate the absence of any diel patterns in feeding for both sexes on both sampling occasions (p > 0.05 in both cases). Moreover, there was no significant differences in gut pigment contents between adult male and females during either of the surveys (p > 0.05). Daily rations of the adult copepods during the two studies were equivalent to <2% (range 0.8 to 1.8%) body carbon per day suggesting that they are consuming alternative carbon sources to meet their daily carbon requirements. The main findings of this study suggest that L. raynerae can be considered as a generalist omnivore.
South Africa is one of six global fish invasion hotspots and as a result, non-native fishes are common components of the fish assemblages in all of the major river systems. The rate of establishment for introduced fish into South African rivers is high (79%) and the vector responsible for the highest establishment rate is interbasin transfer schemes with 80%. Introductions of non-native fish into river systems can negatively affect native fish species through hybridisation, competition for food sources and predation, and the introduction of associated parasites and diseases. The aims of the current study were to provide evidence of the introduction of Labeo capensis into the Crocodile River (West) system, using morphological and molecular techniques, and to record the fish health and gonadosomatic index to determine the invasive status of L. capensis. From the fish health assessment index and gonadosomatic index of L. capensis collected from Olifantsnek Dam, it can be concluded that L. capensis is a healthy reproducing population. Because this fish species can survive and reproduce in newly colonised river systems, it has the potential to compete with the native fish species for food and habitat, but can also hybridise with native Labeo species.
Lernaea cyprinacea Linnaeus, 1758, the anchor worm, is reported parasitising a highly threatened anabantid fish, Sandelia bainsii, which is endemic to the Eastern Cape province of South Africa. Although L. cyprinacea was first recorded in South Africa in 1984, it has, until now, never been reported from any river systems south of the Orange- Vaal River system. We generated mitochondrial 18S rRNA sequences for copepods found on the dorsal surface of a specimen of S. bainsii that was collected on 15 May 2018 from the Zolani River, a tributary of the Buffalo River system in the Amatolo-Winterberg freshwater ecoregion. These copepods were a genetic match to L. cyprinacea. This discovery represents a new locality, as well as a new host record for L. cyprinacea in South Africa. As severe infestations of L. cyprinacea may have potential pathological effects on native fish, its discovery in the Eastern Cape province represents a serious emerging threat to aquatic biodiversity in the Amatolo-Winterberg freshwater ecoregion and the adjacent Cape Fold Ecoregion, which are both global hotspots of imperilled endemic fish.
The intention of this review is to assess the impact of anthropogenic activities on the biodiversity of Lake Abijata. The lake was established as a National Park, together with Lakes Shalla and Chitu, to conserve water birds. It has high pH and electrical conductivity and is hypersaline. It presents an inhospitable limnochemical environment that limits biodiversity, although there are organisms adapted to these hostile conditions. The biodiversity of the lake is threatened by anthropogenic activities. Deforestation, expansion of agriculture, livestock, soda ash extraction and upstream irrigation led to a drop in water level and surface area, a change in physico-chemical and biological conditions, and a general deterioration in ecosystem condition. The phytoplankton community structure has switched from populations of Arthrospira fusiformis to non-Arthrospira fusiformis, zooplankton communities have moved towards small-bodied rotifers, such as Brachionus, Filinia and Lecane spp., the fishery has totally collapsed and birds, such as lesser flamingoes (Phoeniconaias minor Geoffroy) and great white pelicans (Pelecanus onocrotalus), have migrated to nearby lakes. These ecological changes over the past years point to the need for a new conservation and management plan to restore the ecosystem's health. A few recommendations are given for lake management as mechanisms to protect the ecosystem.
Largemouth bass Micropterus salmoides is a highly successful predator that preys on fish and invertebrates. Highly popular with anglers, it is one of the most introduced and invasive fish globally, with strong potential to alter ecosystem structure and functioning. A better understanding of the trophic dynamics of M. salmoides populations is critical for effective management of its ecological impacts in their invasive range. This study investigated the diets and dietary ontogenetic shifts of M. salmoides in two South African dams along with its trophic positioning relative to other fish community members, through stomach content and stable isotope analyses. Micropterus salmoides was a top predator in both dams. In the Mankazana Dam, it depended predominately on insect prey, demonstrating a generalised feeding strategy, with shifts to include increasing proportions of fish prey with increasing size. Contrastingly, in the Wriggleswade Dam, M. salmoides displayed no ontogenetic shifts and preferred Gilchristella aestuaria, likely indicating a shift to a predominantly fish-based diet at smaller sizes, in the presence of small pelagic fish prey. Overall, M. salmoides diet was opportunistic, likely associated with prey morphology and behaviour (associated with refuge availability) and therefore directly linked to prey abundance and availability, which consequently dictated feeding strategy.
A recent proposal that the Australian redclaw crayfish Cherax quadricarinatus and hybrid catfish could potentially control the snail hosts of schistosomiasis has been criticised on the grounds that crayfish pose a severe threat to aquatic ecosystems into which it might be introduced. This note examines the issue further, pointing out that both lack the host-specificity requirement to be a successful biological control agent. The catfish Clarias gariepinus is an omnivore and snails form only a small proportion of its diet; there is no evidence to suggest that it controls snail populations anywhere in Africa. The same applies to other species that have been proposed as biological control agents. Simple laboratory experiments are not an adequate guide to the efficiency of an animal as a biological control agent and detailed ecological investigations would usually demonstrate that few African fish species have this capability.
Different values have resulted in conflicts between anglers and conservation lobbies in the management of trout in South Africa. Key to the conflict is the demarcation of boundaries to areas in which brown trout Salmo trutta and rainbow trout Oncorhynchus mykiss currently occur, or are likely to establish following stocking for angling. To provide a longer-term perspective on these areas, we developed models to link salmonid biological thermal thresholds to elevation. These, when applied spatially using a digital elevation model with a probability of occurrence model, provided the basis for estimating potentially available thermal habitat for these two cold water species. Here, we acknowledge that other variables (stocking history; river connectivity) also play a role in understanding trout distributions. Using a simple scenario of an increase in mean daily water temperatures of 2 °C, we demonstrated that both brown and rainbow trout are likely to exhibit considerable range reductions in the future. Because it is possible that these range restrictions will result in an increasing desire to introduce trout into areas above their current distribution limits for the maintenance of angling opportunities, conservation managers should prioritise these areas, with management interventions seeking to understand what will help to limit introductions.
Morphometric variation among populations of Sarotherodon melanotheron melanotheron across its natural range (Mahin, epe, Lekki, Apese, Kuramo, Lagos, Iyagbe, Ologe, Badagry, Yewa - Nigeria; Be Lagoon - Togo; Idenau - Cameroon, Aheme - Benin; Portonovo - Benin) were studied to assess the level of differentiation of one of the populations that is currently isolated from the rest, the Apese Lagoon population. S. m. melanotheron showed subtle differentiation from some of the other lagoon populations. However, the pattern of variation did not reflect the level of geographical barriers or geographical distance among populations. The characters that form the basis of the differentiation observed were mostly those related to feeding, vision and respiration.
This article presents a fossil diatom-based, semi-quantitative reconstruction of water level fluctuations for Lake Baringo over the past 200 years as a consequence of climatic variations. A 285 cm long sediment core sample was collected using a Rod-Operated Single-drive Stationary Piston corer. Lake level was inferred using indices based on the proportion of planktonic to benthic diatom taxa (P/B ratio). The sediment archive presented distinct zones dominated by planktonic and benthic diatom flora. An initial transgression in the early 19th century was characterised as a shallow water environment dominated by planktonic Aulacoseira spp. This was a response to extreme drought during the late 18th to early 19th century. Mid-19th century was defined by a high lake stand. The late 19th to early 20th centuries experienced low water level following the widely documented aridity at the time. The mid-20th century was marked by a spectacular rise in water level that coincided with remarkably wet years during the early 1960s and late 1970s. The first decade of the 21st century witnessed widespread changes in water level. The proxy records show that lake ramping and drawdown over the years follow approximately 50-year climatic cycles.
Nevirapine (NVP) is one of the HIV antiretrovirals detected recurrently in African surface waters. Liver side effects in humans were reported. Because the effects on fish are unknown, this study investigated the potential effects of NVP on selected biometric indices and liver histology of Oreochromis mossambicus (Mozambique tilapia) in a chronic exposure. Adult fish were exposed to two concentrations of NVP (1.48 and 3.74 µg l −1 ) in a static renewal system under controlled conditions for 30 days. At the end of the exposure, each fish was weighed, the total length recorded, and blood collected from the caudal vein. A standard necropsy was done, selected organs were sampled and weighed, and biometric indices calculated. Liver tissue was processed for histological assessment. Results showed significant differences (p < 0.001) in hepatosomatic indices between the exposed fish and the control, as well as in spleen indices of the fish exposed to the higher NVP concentration (p = 0.008). Liver tissue of exposed fish showed significant histological changes (p < 0.001), including hepatocyte apoptosis, vacuolation, and a mild fibrosis around some of the veins and bile ducts. Nevirapine in African surface waters could have long-term negative effects on the health of fish.
Distichodus antonii is an endemic fish species of the Congo River basin in which the stocks of wild populations are threatened by overfishing pressure. Knowledge of its reproductive biology would be useful in consideration of conservation and management options for the species. Therefore, this study investigated changes in ovarian activity and levels of steroid profiles in wild populations in relation to variation in temperature and rainfall. Adult females (n = 101, body weight of 3 183 ± 14.75 g, SE) were captured monthly over one year (2013-2014). Apart from evaluation of oocyte diameters and gonad developmental stages, gonado-, hepato-, lipososomatic indices (GSI, HSI, LSI) and plasma levels of sex steroids (testosterone-T, estradiol-17β-E2) were determined. The results suggested a synchronous development of oocytes with two annual reproductive seasons over the one-year study. Plasma T and E2 levels peaked during spawning periods likely reflecting active oogenesis. The highest values of morphosomatic indices were observed during the longest rainfall period in September, and were associated with high steroidogenic activity evidenced by increased E2 production. In addition, more vitellogenic oocytes (September and October) were observed during the latter season than during the short rainy season (in May).