Diversity, distribution and extinction risk of native freshwater fishes of South Africa.

Extinction risk for 101 valid species and 18 unique genetic lineages of native freshwater fishes of South Africa was assessed in 2016 following the IUCN Red List criteria. An additional five species (three new species that were described and two species that were revalidated subsequent to the 2016 assessments) were assessed in the present study. A synthesis of the outcome of the assessments of the 106 valid species and 18 genetic lineages indicates that 45 (36%) of South Africa's freshwater fish taxa are threatened (7 Critically Endangered, 25 Endangered, 13 Vulnerable). Of the remaining taxa, 17 (14%) are listed as Near Threatened, 57 (46%) are Least Concern and five (4%) are Data Deficient. More than 60% of the endemic taxa are threatened. The Cape Fold Ecoregion has the highest proportion of threatened taxa (67%) due to the existence of a unique assemblage of narrow-range endemic species. Galaxias and Pseudobarbus have the highest number of highly threatened taxa as most of the species and lineages in these genera are classified as either CR or EN. Major threats to the native freshwater fishes of the country are invasive fish species, deterioration of water quality, impoundments and excessive water abstraction, land use changes and modification of riverine habitats. Immediate conservation efforts should focus on securing remnant populations of highly threatened taxa and preventing deterioration in threat status, because recovery is rare. Accurate delimitation of species boundaries, mapping their distribution ranges, improved knowledge of pressures and long-term monitoring of population trends need to be prioritised to generate credible data for the 2026 IUCN threat status assessments and designation of important fish areas as part of the National Freshwater Ecosystem Priority Areas (NFEPA) initiative.

Four new species of Serranochromis (Teleostei: Cichlidae) from the Cuanza and Okavango river systems in Angola, including a preliminary key for the genus.

The present study describes Serranochromis alvum n. sp., Serranochromis swartzi n. sp., Serranochromis cuanza n. sp., and Serranochromis cacuchi n. sp. from Angolan tributaries of the Cuanza and Okavango systems in Angola. The presence of four or five scale rows between the posterior margin of the orbit and the ascending arm of the preoperculum, the presence of widely set unicuspid teeth on the jaws, widely separated gill rakers, and anal fins with egg ocelli place these four species in Serranochromis. The Serranochromis described herein are distinguishable based on a combination of morphological and meristic characters, as well as pigmentation patterns. The interorbital width (14.3-15.9 % HL) of S. alvum is narrower than that of S. swartzi (17.6-19.8), S. cuanza (16.3-18.0), and S. cacuchi (20.0-21.7). Moreover, the interorbital width of S. cacuchi is greater than the other three described species. Serranochromis swartzi has a smaller preorbital depth (16.2-18.9 % HL) and snout length (29.6-31.9 % HL) than Serranochromis cuanza (PD 19.1-22.2, SNL 35.2-39.6 % HL). Serranochromis alvum is known only from the type locality at Cuito-Cuanavale at the junction of the Cuito and Cuanavale rivers, tributary to the Okavango River in Angola. Serranochromis swartzi is known only from the type locality in the Cuanza River, Angola. Serranochromis cuanza is restricted to the Cuanza River, below Capanda Dam, Angola, while S. cacuchi is known only from the Cacuchi River, a tributary of the Cuchi-Cubango River in Angola. The limited distribution of all four species and the absence of many congeners suggest, that in addition to previous studies that invoked a lacustrine speciation model, vicariance through drainage isolation seems to have played an important role in driving speciation in this group. The minimum polygon clusters that are formed when the first principal components of the meristic data are plotted against the second sheared principal components of the morphometric data show separation of the four new species.

Re-elevation to species level and redescription of Serranochromis jallae and Serranochromis robustus (Teleostei: Cichlidae).

Serranochromis robustus robustus from Lake Malawi and Serranochromis robustus jallae from Zambia were compared using morphological data. We re-elevated S. robustus jallae to species based on the following. Serranochromis robustus generally has a longer lower jaw (50.7-59.6% HL) than S. jallae (49.2-52.7% HL). Serranochromis robustus is not as deep-bodied as S. jallae as evidenced by the distance between the posterior insertion of the dorsal fin and the posterior insertion of the anal fin (13.4-15.1% SL in S. robustus vs. 14.9-18.4% SL in S. jallae). Additionally, S. robustus has a narrower least caudal peduncle depth (10.9-12.8% SL) than S. jallae (11.3-14.2% SL); the least caudal peduncle depth of all S. robustus was less than 12.8% SL while, except for the smallest specimen of S. jallae (88.1 mm SL), the least caudal peduncle depth was greater than 13.2% SL. Adults in breeding color of Serranochromis robustus are blue/green laterally, while adults in breeding color of S. jallae are yellow/green laterally. The marginal bands on the dorsal and caudal fins of S. jallae are bright orange in specimens from the Okavango River system and creamy yellow in Upper Zambezi specimens. In S. robustus, there is a yellow marginal band on the dorsal fin.

A review of the Pseudobarbus afer (Peters, 1864) species complex (Teleostei, Cyprinidae) in the eastern Cape Fold Ecoregion of South Africa.

The Eastern Cape redfin, Pseudobarbus afer, has long been considered to be a single widespread and variable species occurring in multiple isolated river systems in the Cape Fold Ecoregion (CFE) at the southern tip of Africa. Mitochondrial cytochrome b and control region sequence data of individuals from populations currently assigned to Pseudobarbus afer across the species' distribution range revealed existence of four deeply divergent taxonomic units: (i) the Mandela lineage confined to the Sundays, Swartkops and Baakens river systems, (ii) the Krom lineage endemic to the Krom River system, (iii) the St Francis lineage occurring in the Gamtoos and adjacent river systems, and (iv) the Forest lineage occurring in several coastal river systems from the Tsitsikamma to the Klein Brak River system. The Forest lineage is closely related to Pseudobarbus phlegethon from the Olifants River system on the west coast of South Africa, suggesting that it does not belong to Pseudobarbus afer s.l. Herein we focus on the three lineages within the Pseudobarbus afer s.l. complex and provide new diagnosis for Pseudobarbus afer s.s (Mandela lineage), revalidate Pseudobarbus senticeps (Krom lineage) as a distinct species, and describe a new species Pseudobarbus swartzi (St Francis lineage). The three species exhibit subtle differences, which explains why they were previously considered to represent a single variable and widespread species. Pseudobarbus senticeps differs from both Pseudobarbus afer and Pseudobarbus swartzi by having fewer (i.e. larger) scales (25-33, mode 29 lateral line scale series; 10-12, mode 11 circumpeduncular scales) and presence of a lateral stripe which terminates in a conspicuous triangular blotch at the base of the caudal fin. Long barbels which reach or surpass the vertical through the posterior edge of the eye further separate Pseudobarbus senticeps from Pseudobarbus afer s.s. which possesses simple short barbels which do not reach the vertical through the posterior margin of the eye. Pseudobarbus afer s.s differs from Pseudobarbus swartzisp. n. by possession of fewer scale rows along the lateral line (29-35, mode 32 vs 34-37, mode 36 in Pseudobarbus swartzi), fewer scales around the caudal peduncle (12-16, mode 12 vs 13-17, mode 16 in Pseudobarbus swartzi) and a distinct mesh or net-like pigmentation pattern on latero-ventral scales.

Multiple colonisations of the Lake Malawi catchment by the genus Opsaridium (Teleostei: Cyprinidae).

It has been proposed that the fish faunas of African rivers assemble through multiple colonisation events, while lake faunas form additionally through intralacustine speciation. While this pattern has been established for many lineages, most notably cichlids, there are opportunities to further investigate the concept using phylogenies of congeneric endemic species within ancient lake catchments. The Lake Malawi catchment contains three river-spawning cyprinids of the genus Opsaridium, two of which are endemic. These species differ in body size, migratory behaviour and habitat use, but it has never previously been tested if these represent a monophyletic radiation, or have instead colonised the lake independently. We placed these species in a broader phylogeny of Opsaridium and the related genus Raiamas, including all known species from the river systems surrounding Lake Malawi. Our results suggest that each of the species has independently colonised the lake catchment, with all three taxa having well-defined sister taxa outside of the lake, and all sharing a common ancestor ∼14.9million years ago, before the Lake Malawi basin started to form ∼8.6million years ago. Additionally, the results strongly support previous observations that Opsaridium is not a monophyletic group, but instead contains Raiamas from the Congo drainage. Together these results are supportive of the concept that river fish faunas within African catchments are primarily assembled through a process of accumulation from independent origins, rather than within-catchment speciation and adaptive radiation. In light of these results we also suggest there is scope for a re-evaluation of systematics of both Opsaridium and Raiamas.

A new species of redfin (Teleostei, Cyprinidae, Pseudobarbus) from the Verlorenvlei River system, South Africa.

Pseudobarbusverloreni, a new species, is described from material collected in the Verlorenvlei River system on the west coast of South Africa. It differs from its congeners (except Pseudobarbusskeltoni, Pseudobarbusburchelli, and Pseudobarbusburgi) by the presence of two pairs of oral barbels. Pseudobarbusverloreni sp. n. can be distinguished from the three currently described double barbeled Pseudobarbus species by the following combination of characters: pigment pattern, generally deeper body relative to standard length, a longer intestine associated with the deeper body form, shorter snout relative to head length, and much shorter anterior barbels relative to head length. The new species is distinguished from Pseudobarbusburgi in the neighbouring Berg River system by its longer head and longer pre-dorsal length. It seems as if Pseudobarbusverloreni sp. n. has been extirpated from the Langvlei River system and face several threats to its survival in the Verlorenvlei River system.

Cryptic diversity of African tigerfish (genus Hydrocynus) reveals palaeogeographic signatures of linked neogene geotectonic events.

The geobiotic history of landscapes can exhibit controls by tectonics over biotic evolution. This causal relationship positions ecologically specialized species as biotic indicators to decipher details of landscape evolution. Phylogeographic statistics that reconstruct spatio-temporal details of evolutionary histories of aquatic species, including fishes, can reveal key events of drainage evolution, notably where geochronological resolution is insufficient. Where geochronological resolution is insufficient, phylogeographic statistics that reconstruct spatio-temporal details of evolutionary histories of aquatic species, notably fishes, can reveal key events of drainage evolution. This study evaluates paleo-environmental causes of mitochondrial DNA (mtDNA) based phylogeographic records of tigerfishes, genus Hydrocynus, in order to reconstruct their evolutionary history in relation to landscape evolution across Africa. Strong geographical structuring in a cytochrome b (cyt-b) gene phylogeny confirms the established morphological diversity of Hydrocynus and reveals the existence of five previously unknown lineages, with Hydrocynus tanzaniae sister to a clade comprising three previously unknown lineages (Groups B, C and D) and H. vittatus. The dated phylogeny constrains the principal cladogenic events that have structured Hydrocynus diversity from the late Miocene to the Plio-Pleistocene (ca. 0-16 Ma). Phylogeographic tests reveal that the diversity and distribution of Hydrocynus reflects a complex history of vicariance and dispersals, whereby range expansions in particular species testify to changes to drainage basins. Principal divergence events in Hydrocynus have interfaced closely with evolving drainage systems across tropical Africa. Tigerfish evolution is attributed to dominant control by pulses of geotectonism across the African plate. Phylogenetic relationships and divergence estimates among the ten mtDNA lineages illustrates where and when local tectonic events modified Africa's Neogene drainage. Haplotypes shared amongst extant Hydrocynus populations across northern Africa testify to recent dispersals that were facilitated by late Neogene connections across the Nilo-Sahelian drainage. These events in tigerfish evolution concur broadly with available geological evidence and reveal prominent control by the African Rift System, evident in the formative events archived in phylogeographic records of tigerfish.

Phylogeny and biogeography of the genus Pseudobarbus (Cyprinidae): shedding light on the drainage history of rivers associated with the Cape Floristic Region.

Relationships among the historically isolated lineages of Pseudobarbus were reconstructed using molecular and morphological data. Contradictions between the molecular and morphological phylogenies suggest convergent evolution and homoplasy in some morphological characters. The earliest divergence in Pseudobarbus was between P. quathlambae in Lesotho and the rest of the genus associated with the Cape Foristic Region in South Africa. A close relationship between P. phlegethon from the Olifants River system on the west coast of South Africa and a lineage of P. afer from small river systems in Afrotemperate Forests on the south coast, can only be explained through previous occurrence and subsequent extinction of ancestral populations in the Gourits River system. Several river systems had confluences before reaching lower sea levels, most notably during the last glacial maximum about 18,000 years ago, explaining closely related populations across different river systems. Mainly river capture explains shared lineages across river systems that did not share a common confluence during lower sea levels.