Schilbe Intermedius Research Articles

Environmental DNA biomonitoring in biodiversity hotspots: A case study of fishes of the Okavango Delta

AbstractThe Okavango Delta is the largest freshwater wetland in southern Africa and a recognized biodiversity hotspot and UNESCO World Heritage Site. The region is extremely rich in floral and faunal diversity, including a fish fauna of ~90 species in 15 families, that also support recreational and subsistence fishing. Anthropogenic pressures and invasive species threaten the unique biodiversity and ecosystem services that the Delta provides, necessitating biomonitoring tools that can provide broad community‐level diversity insights. Here, we utilize environmental DNA metabarcoding of aquatic eDNA using the MiFish 12S rRNA primers, to investigate fish communities and also sequenced 211 mtDNA 12S barcodes for 74 species across 36 genera of fishes from the region. Metabarcoding recovered 11 of 15 families, with 40 species detected across 23 genera, representing ~50% of known diversity, with the mtDNA 12S fragment able to delineate all genera (except for the cichlid genera Serranochromis and Pharyngochromis that comprised a single clade) and most species, except for some in the Clarias, Enteromius, Labeo, Lacustricola, and Petrocephalus genera. Generally, abundant and wide‐spread taxa such as Clarias spp. and Marcusenius altisambesi, amongst others, were often detected in the surveys, with other species, including Zaireichthys kavangoensis, Schilbe intermedius, and Labeo sp. detected less frequently. Dissolved oxygen, temperature, and dissolved organic solids were positively correlated with community diversity, highlighting the influence of environmental factors in shaping fish communities in the region. Further, there was strong variability in the eDNA signal across only 1000 m, suggesting that future surveys need to consider spatio‐temporal aspects of sample collection. Our study highlights the potential of eDNA metabarcoding for surveying aquatic biodiversity in the Okavango Delta, particularly within the context of baseline biodiversity inventories, that underpin conservation and management initiatives. As such, we provide a number of recommendations that can help structure future sampling efforts in the region.

Nutrient composition of common fish species in the Okavango Delta: potential contribution to nutrition security

Fish can be a key strategy in addressing the global food and nutrition insecurity challenges. Fish nutrient data are critical for policy development targeting to reduce these problems. Despite this, much of the published studies on nutritional characteristics of fish have focused on marine ecology and there is little information on natural freshwater fish habitats like inland delta areas. This study investigated the nutrient composition of Okavango Delta fishes and their potential contribution to the recommended nutrient intake. Fish species sampled were Clarias ngamensis, Oreochromis andersonii, Schilbe intermedius, Marcusenius altisambesi, Brycinus lateralis, Barbus poechii and Tilapia sparrmanii. The nutrients analyzed were moisture, ash, proteins, Na, K, Ca, Mg, P and Zn. The small fishes (B. lateralis and B. poechii) had higher mineral content; Ca (643–968 mg/100 g), Mg (47–49 mg/100 g) and Zn (2.8–3.6 mg/100 g) compared to the larger species with average mineral content; Ca (73–460 mg/100 g), Mg (23–35 mg/100 g), Zn (1.2–2.9 mg/100 g). The most nutrient-dense species recognized were B. poechii and B. lateralis followed by the large species, M. altisambesi. These species illustrated the potential to contribute 80–121% Ca, 32–47% Mg and 70–150% Zn of the recommended nutrient intake to children (1–9 years), pregnant women and the elderly (65 + years). The study recommends prioritizing small and some large species (M. altisambesi and T. sparrmanii) for polyculture systems, primarily for securing food and nutrition security for local communities.

The Fish Fauna of the Future Large Size Reservoir of Ouessa, on the Mouhoun River, Burkina Faso

Reliable and basic information on fish are required for the sustainable management of a fishery. For this reason, the fish fauna of the future reservoir of Ouessa in the low section of the Mouhoun River, Burkina Faso is studied. In order to describe the fish community, the fish were sampled in March 2020 thanks to cast nets and gill nets. They were sorted into species and each fish was weighted at the nearest 0.1 g and its total length measured at the nearest mm. The landings of commercial fishermen were also observed. In total, 1059 fishes were collected and grouped into 42 species, 27 generas and 16 families. The dominant species were Synodontis nigrita, Synodontis schall, Marcusenius senegalensis, Schilbe intermedius, Brycinus nurse and Alestes baremoze. However, the compilation of diverse sources suggests the presence of nearly 70 species. The index of Shannon-Weaver (3.97), the values of the condition factor, the fish size and the presence of intolerant species indicate the relatively good conditions of the aquatic ecosystem. Among the 24 dominant species, 54% have a positive allometric growth, 42% a negative allometric growth and 0.04 an isometric growth. This study builds the basis of sustainable management of the future reservoir of Ouessa that is planned to be the largest one of the country (40,000 ha large).

Length-weight relationships of 19 fish species from two tropical artificial reservoirs (Manantali and Selingue) in Mali, West Africa

Length-weight relationships (LWRs) were estimated for 19 fish species sampled from two artificial reservoirs (Manantali and Selingue) in Mali: Brycinus leuciscus, B. macrolepidotus, B. nurse, Chrysichthys auratus, C. nigrodigitatus, Coptodon zillii, Distichodus brevipinnis, D. rostratus, Hemichromis fasciatus, Hydrocynus forskahlii, Labeo coubie, L. senegalensis, Lates niloticus, Mormyrus rume, Sarotherodon galilaeus, Schilbe intermedius, S. mystus, Synodontis schall, S. sorex. The fish were collected between June 2002 and October 2003 during three experimental fishing campaigns using gillnets deployed overnight. All fish were measured (total length) to the nearest mm and weighed to the nearest g (total weight). Coefficients of determination of the LWRs (r²) were mostly high (> 0.9). The values of the allometry coefficient b ranged from 2.651 (Chrysichthys auratus) to 3.270 (Brycinus leuciscus). This study provides new information about LWRs of two fish species, which have been published but are not yet available in Fishbase (Distichodus brevipinnis and Mormyrus rume)

DNA Barcoding Silver Butter Catfish (Schilbe intermedius) Reveals Patterns of Mitochondrial Genetic Diversity Across African River Systems

The silver butter catfish (Schilbe intermedius) is widely distributed across African river systems. To date, information on its mitochondrial genetic diversity, population structure, and historical demography are not well-established. Herein, we combined newly generated mitochondrial cytochrome c oxidase (COI) subunit I gene sequences with previously published COI sequences in the global databases to reconstruct its phylogeography, population genetic structure, and historical demography. Results from the mtDNA phylogeography and species delimitation tests (Cluster algorithm – Species Identifier, Automatic Barcode Gap Discovery and Poison Tree Process model) revealed that S. intermedius comprises at least seven geographically defined matrilines. Although the overall haplotype diversity of S. intermedius was high (h = 0.90), results showed that East (Kenya) and West (Nigeria) African populations had low levels of haplotype diversity (h = ~0.40). In addition, population genetic polymorphism and historical demographics showed that S. intermedius populations in both East and West Africa underwent severe contractions as a result of biogeographic influences. The patterns of genetic diversity and population structure were consistent with adaptive responses to historical biogeographic factors and contemporary environmental variations across African river systems. This is suggestive of the influence of historical biogeographic factors and climatic conditions on population divergence of S. intermedius across African river systems. Given our discovery of previously underappreciated diversity within S. intermedius, we recommend that this species be considered for increased conservation and management.

Biological aspects of Schilbe intermedius (Ruppell, 1832) in the Nyanza Gulf of Lake Victoria, Kenya

AbstractSilver butter catfish (Schilbe intermedius) is an indigenous fish species in Lake Victoria. It has a good economic value because of the quality and freshness of its flesh, increasing its demand for consumption. It is potamodromous, with its stock in the lake declining because of overexploitation by the use of illegal fishing gears at the river mouths on their way to spawning areas. Fish samples (321) were obtained from commercial gill net (1.5–3 in.) fishers within Nyanza gulf. The fish samples were weighed (g) and measured (cm), dissected and sex determined by visual inspection of the gonads. Ovaries for mature female fish specimens were preserved for analysis of fecundity. Fecundity was determined by the gravimetric technique. The mean (±SE) length and weight for all fish were 18.2 ± 0.2 cm TL and 51.9 ± 1.9 g, respectively. The female fish (20.0 ± 0.2 cm) were significantly (F = 199.80, p < .05) larger than the males (15.9 ± 0.1 cm). Similarly, the females (68.8 ± 2.6 g) were significantly (F = 152.61, p < .05) heavier than the males (30.93 ± 1.02 g). The overall sex ratio was 1.23:1.0 (female:male). The length frequency exhibited a unimodal distribution, with the modal class between 16 and 18 cm for either sex. The regression slope (b) of the length–weight relationship was 3.2, 3.1 and 3.0 for all fish, females and males. The absolute fecundity ranged from 6,510 to 59,818 eggs, with a mean of 34,473 eggs. The length at 50% maturity was estimated to be 16.0 cm (female) and 18.0 cm (male) fish. The mean length and size at maturity of S. intermedius have declined, likely attributable to fishing effects, changes in food resources, competition and predation. Thus, the present study provided relevant biological data of S. intermedius, which is currently limited for this region.

A new species of Clinostomum Leidy, 1856 based on molecular and morphological analysis of metacercariae from African siluriform fishes

In the Afrotropic region, the genus Clinostomum is represented by four accepted and four unnamed species distinguished using molecular data. Here, we describe one of the four unnamed species as Clinostomum ukolii n. sp. based on metacercariae from siluriform fishes (Synodontis batensoda, Schilbe intermedius) collected in Nigeria and South Africa. The new species is distinguished by molecular data (39 new sequences of partial cytochrome c oxidase I≥ 6.7% divergent from those of other species) and morphological differences from named and unnamed species in the same region. Metacercariae of C. ukolii n. sp. can be distinguished based on size, tegumental spines, and various aspects of the genital complex, including its position, lobation of the anterior testis, and the disposition and shape of the cirrus pouch. Although descriptions of new species of digeneans are typically based on the morphology of adults, we argue that in cases where data are available from metacercariae from regionally known species, new species can be described based on metacercariae, particularly when supported by molecular data, as here. Moreover, sub-adult reproductive structures can be clearly visualized in metacercaria of Clinostomum. Considering metacercariae as potential types for new species could advance clinostome systematics more rapidly, because metacercariae are encountered much more often than adults in avian definitive hosts.

Effect of Dietary Protein on Growth

The captive breeding of the Silver catfish Schilbe intermedius was envisaged to promote the aquaculture and to reduce the overfishing of this endangered species. S. intermedius fingerlings were fed various dietary protein levels to investigate their growth performance, feed utilization and carcass proximate composition. Fish meal and casein were the sources of protein used in the study. Six isocaloric experimental diets containing 25%~60% crud protein (CP) diet have been  fed to three-replicate six groups of forty (40) fishes (mean weight: 1.640 ± 0.015 g) for 8 weeks. Both percent weight gain and feed efficiency ratio significantly increased with increasing dietary protein levels up to 45%, while there were no significant differences for protein levels from 45 to 60%. Growth performances and nutrient utilization parameters of fingerlings fed different diets varied significantly (P < 0.05) and the highest growth performance and nutrient utilization were obtained with fish fed on a 45% CP diet. The second order polynomial regression between dietary protein and specific growth rate (SGR) indicated that protein requirements of S. intermedius fingerlings ranged from 42.5 to 53% of diet. The highest protein content of the fish carcasses was found in fish fed 45% dietary protein and there was not significantly different (P > 0.05) with that of fish fed 60% dietary protein. Lipid content increased with increasing dietary protein levels. The dry matter and protein content of the initial sample were significantly higher (P > 0.05) than the values after feeding the fish with experimental diets.

Update of Ichthyofauna and its Conservation Status in the Aghien Lagoon, Côte d’Ivoire

Abstract This study focused on the diversity of fish fauna, its conservation status and its vulnerability in the Aghien freshwater lagoon (southeast of Côte d'Ivoire). For the fish data collection, two sampling approaches were used: experimental fishing and artisanal fishing. As a result, 80 species observed in this lagoon are distributed into 55 genera, 27 families and 10 orders. The best represented orders are the Perciformes, Siluriformes, Osteoglossiformes, Characiformes, Cyprinodontiformes and Pleuronectiformes. The Cichlidae, Mormyridae and Clupeidae represented the best diversified family. With an occurrence of 100%, the most frequent species are: Brycinus longipinnis, Chrysichthys nigrodigitatus, Pellonula leonensis, Schilbe intermedius and S. mandibularis. In the whole fish population, according to IUCN red list, four species where described as Near Threatened (Coptodon walteri, Marcusenius furcidens, Galeoides decadactylus and Cynoglossus senegalensis), four as Vulnerable (B. brevis, Rhexipanchax nimbaensis, Enteromius raimbaulti and Tilapia busumana) and one as Endangered species (Pseudotolithus senegalensis). These categories of species that have a conservation interest according to the IUCN Red List represent respectively 10.26% of the whole population. Fish population of the Aghien Lagoon are divided into seven classes ranging from “low” to “very high” vulnerability, regarding the vulnerability to stress due to fishing pressure.

DNA barcoding of economically important freshwater fish species from north-central Nigeria uncovers cryptic diversity.

This study examines the utility of morphology and DNA barcoding in species identification of freshwater fishes from north‐central Nigeria. We compared molecular data (mitochondrial cytochrome c oxidase subunit I (COI) sequences) of 136 de novo samples from 53 morphologically identified species alongside others in GenBank and BOLD databases. Using DNA sequence similarity‐based (≥97% cutoff) identification technique, 50 (94.30%) and 24 (45.30%) species were identified to species level using GenBank and BOLD databases, respectively. Furthermore, we identified cases of taxonomic problems in 26 (49.00%) morphologically identified species. There were also four (7.10%) cases of mismatch in DNA barcoding in which our query sequence in GenBank and BOLD showed a sequence match with different species names. Using DNA barcode reference data, we also identified four unknown fish samples collected from fishermen to species level. Our Neighbor‐joining (NJ) tree analysis recovers several intraspecific species clusters with strong bootstrap support (≥95%). Analysis uncovers two well‐supported lineages within Schilbe intermedius. The Bayesian phylogenetic analyses of Nigerian S. intermedius with others from GenBank recover four lineages. Evidence of genetic structuring is consistent with geographic regions of sub‐Saharan Africa. Thus, cryptic lineage diversity may illustrate species’ adaptive responses to local environmental conditions. Finally, our study underscores the importance of incorporating morphology and DNA barcoding in species identification. Although developing a complete DNA barcode reference library for Nigerian ichthyofauna will facilitate species identification and diversity studies, taxonomic revisions of DNA sequences submitted in databases alongside voucher specimens are necessary for a reliable taxonomic and diversity inventory.

English

In Cote d’Ivoire, the Aghien Lagoon is under heavy fishing pressure. Mortality, recruitment pattern and exploitation rate of Schilbe mandibularis and Schilbe intermedius were investigated in this lagoon. Fish samples of both sexes (N = 575) were collected monthly between June 2014 and May 2015 from artisanal and experimental captures. Natural mortality was higher in S. intermedius (M = 0.89 years-1) than in S. mandibularis (M = 0.58 years-1). The population of S. intermedius was more vulnerable to fishing (F = 2.90 years-1) than S. mandibularis (F = 0.51 years-1). The Z/K ratio (Z/K = 2.65 for S. mandibularis; Z/K = 4.85 for S. intermedius) indicated that mortality was predominant over growth for the two species. The recruitment pattern showed one Gauss curve translates was continuous for each species. For S. mandibularis, the exploitation rate (E = 0.47) was close to E 0.1 (E 0.1 = 0.46), indicating that S. mandibularis’s stock was in an optimum state of exploitation. However, for S. intermedius, Emax was lower (Emax = 0.57) than the exploitation rate (E = 0.77). This result reflected overexploitation of this species. Key words: Schilbe mandibularis, Schilbe intermedius, mortality, recruitment, exploitation, Aghien Lagoon.

Gill net catch composition and catch per unit effort in Flag Boshielo Dam, Limpopo Province, South Africa

Gill net surveys were conducted in 2013 to determine species composition and fisheries potential of Flag Boshielo Dam. Species contributing the most towards total biomass were Labeo rosae (40%), Oreochromis mossambicus (15%), Schilbe intermedius (10%) and Labeobarbus marequensis (9.8%). Catch per unit effort for gill nets set at night (4.4 ± 0.6 kg·100 m-net −1 ·hr −1 ) was significantly higher ( P < 0.05) than for those set during the day (0.9 ± 0.1 kg·100 m-net −1 ·hr −1 ). Total fish biomass captured in 30, 50, 70, 90 and 110 mm mesh sized nets was 3.1, 31.5, 43.5, 23.5 and 16.1 kg, respectively. Catch in gillnets with mesh sizes ≥ 70 mm was dominated by L. rosae comprising 60% of the catch in the 70 mm mesh; L. rosae (40%) and O. mossambicus (36%) in the 90 mm mesh; and O. mossambicus (40%) and Clarias gariepinus (40%) in the 110 mm mesh. If a small-scale fishery were to be initiated, it is recommended that mesh sizes should exceed 70 mm and that further research on the biology and ecology of the main target species and of the current utilisation of the fishery be conducted to guide sustainable utilisation. Keywords: Arabie Dam, CPUE, fish composition, net selectivity, inland fisheries

Fish community dynamics in an inland floodplain system of the Okavango Delta, Botswana

Tropical floodplain fish populations fluctuate at temporal scales and understanding the variability in these systems will contribute to comprehensive management of these resources. Therefore, the aim of this study was to assess the dynamics of a floodplain fish assemblage. Data were collected using standard methods between 1999 and 2009 from the delta's panhandle. Various analytical tools (e.g. CCA, SIMPER, ANOVA, etc.) were used to assess fish assemblage dynamics at seasonal and annual scales. ANOVA and cluster analyses showed that the fish assemblage underwent significant changes along the seasonal hydrograph, while index of relative aboundance (%IRI) revealed that the fish assemblage was dominated by Clarias gariepinus, Schilbe intermedius and Hydrocynus vittatus respectively. These species, including Clarias ngamensis and Marcusenius altisambesi, contributed more than 50% to variations in fish assemblage structure along the seasonal hydrograph (based on SIMPER analysis). Furthermore, canonical correspondence analysis (CCA) revealed a significant (p=0.004) association between environmental factors and fish assemblage structure. CCA analysis also showed that spawning for different species is associated with various environmental factors. Annually, results showed that C. gariepinus dominated the fish assemblage during low flood years, while S. intermedius dominated during high flood years. Detrended correspondence analysis (DCA) showed that the hydrological gradient had a significant effect on fish assemblage structure at an annual scale, while SIMPER analysis established significant variations in fish assemblage structure among years characterized by different hydrological features. One major conclusion we made was that fish assemblages are stochastically different at an annual scale. This study contributes knowledge to floodplain fish ecology and thus enhances fisheries management.

Pesticide residues in water, sediment and fish from Tono Reservoir and their health risk implications.

Levels of organochlorine (OC) and organophosphorus (OP) pesticide residues in fish, sediments and water and their health risk associated with the consumption of the fish from the Tono Reservoir, Ghana were evaluated. The analytical methods included solvent extraction of the pesticide residues using ultrasound sonication and soxhlet extraction and their subsequent quantification using GC equipped with electron capture detector and pulse flame photometric detector after clean-up on activated silica gel/anhydrous sodium sulphate. A total of 29 pesticides comprising 16 OCs and 13 OPs were analyzed, out of which aldrin, p,p′-DDE and p,p′-DDD were detected in fish and sediment samples. The results showed that all the residues in water had their concentrations below the detection limit. Mean concentrations of organochlorine pesticide (OCP) residues in fish ranged from 0.017 to 0.17, 0.043 to 0.30, 0.027 to 0.243 and 0.097 to 0.263 µg/g in Sarotherodon galilaeus, Clarias anguillaris, Schilbe intermedius and Marcusenius senegalensis respectively. Mean concentrations of organophosphates pesticides ranged from 0.080 to 0.090, 0.080 to 0.087 and 0.050 to 0.063 µg/g in C. anguillaris, S. intermedius and M. senegalensis respectively. The level of chlorpyrifos in S. galilaeus was 0.160 µg/g. Mean concentrations of OCP residue in sediments ranged from 0.047 to 0.090 µg/g. Aldrin recorded the highest level while p,p′-DDD recorded the lowest level. The mean concentrations for all the detected residues were below the WHO/FAO maximum residue limits. Health risk estimation revealed that aldrin in M. senegalensis had great potential for systemic toxicity to consumers.

Validation of the periodicity of growth zone formation in the otoliths of four fish species from the Upper Zambezi ecoregion, southern Africa

In the Upper Zambezi and Okavango ecoregions, Brycinus lateralis, Hepsetus cuvieri, Schilbe intermedius and Serranochromis macrocephalus are important in subsistence fisheries, while S. intermedius and S. macrocephalus are often caught in commercial catches. Despite their importance, there is little information on their age and growth and age validation. Growth zone deposition rate in otoliths of B. lateralis, H. cuvieri, S. intermedius and S. macrocephalus was validated as annual using edge analysis in this study. Annual deposition of growth zones was corroborated by a fluorochrome marking experiment. Both methods demonstrated that one growth zone was deposited annually. Edge analysis demonstrated that the highest proportion of opaque zones was detected between August and December, most likely as a result of slow growth during lower temperature water during the preceding winter. With growth zone deposition validated as annual, future research should focus on determining the growth, maturity and mortality rates of these species, parameters which are important for their management.

Ecology, fish and fishery of Lake Liambezi, a recently refilled floodplain lake in the Zambezi Region, Namibia

Lake Liambezi (300 km2) refilled in 2009 after a prolonged 22-year dry period. Its aquatic macrophyte populations, fish fauna and fishery shortly after refilling are described. The emergent aquatic macrophyte Phragmites australis formed dense stands covering large parts of the lake, while extensive beds of submerged Lagarosiphon ilicifolius and Najas horrida occurred in shallower areas. Twenty-nine fish species were recorded in experimental gillnets. Catches were dominated by Brycinus lateralis and Schilbe intermedius, contributing 39.5% and 38.5% by weight, respectively. Large-meshed (3–4.5 inch) monofilament and multifilament gillnets emulating those used in the commercial fishery caught mostly Oreochromis andersonii (42.7% by weight) and Serranochromis macrocephalus (28.3% by weight), respectively. Commercial gillnet catch per unit effort (CPUE) averaged 7.0 kg 100-m net−1 night−1, and the annual yield for 2011/2012 was estimated at 2 700 tonnes. Aquatic macrophytes and fishes quickly recolonised the lake and, just two years after refilling, the lake supported a thriving fishery that yielded 4.5 times more than the 600 tonnes recorded in 1974.

English

Developing countries remain overwhelmed by nutritional problems caused mainly by poverty, natural disasters and political instabilities. The aim of this study was to determine essential mineral content of some common fish species in the Okavango Delta, Botswana and assess their potential in enhancing mineral intake. Atomic Absorption Spectrometry was used for determination of Ca, Mg, Fe, Zn, Cu, Mn; flame photometry for Na and K; UV-VIS Spectrometry for P. Marcusenius altisambesi, Schilbe intermedius, Brycinus lateralis, Oreochromis andersonii, Barbus poechii. Only edible flesh was analysed for large fish (&gt;130mm) while small fish (&lt;130mm) were analysed whole. Single factor ANOVA analyses show that all minerals analysed except copper varied significantly between species, (p&le;0.05) and the small species, Barbus poechii has the highest mineral content. The concentration ranges of minerals were within FAO mean concentration ranges for fish and comparable to values obtained from other previous studies. The results show that fishes of Chanoga have a good supply of minerals and can be used for enhancing mineral intake and protecting the community from mineral deficiency diseases.&nbsp; &nbsp; Key words: Fish species, macro-nutrients, micro-nutrients, mineral content, Okavango Delta. &nbsp

Studies on ascaridid, oxyurid and enoplid nematodes (Nematoda) from fishes of the Okavango River, Botswana.

Based on light and scanning electron microscopical studies, eight species (five adult and three larval) of nematodes belonging to the Ascaridida, Oxyurida and Enoplida were collected from fishes of the Okavango River, Botswana, namely Falcaustra similis Moravec et Van As, 2004, Atractidae gen. sp. (only female) (both Cosmocercoidea), Cucullanus sp. (only female) (Seuratoidea), Cithariniella longicaudata sp. n., Synodontisia annulata sp. n. (both Oxyuroidea), Contracaecum sp. third-stage larvae, third-stage larvae of Galeiceps sp. (both Ascaridoidea) and Eustrongylides sp. fourth-stage larvae (Dioctophymatoidea). The new species Citharinella longicaudata (type host Schilbe intermedius Rüppel) is mainly characterised by the shape and size of cephalic papillae and the spicule 108 µm long, and Synodontisia annulata (type host S. intermedius) by the shape of cephalic papillae, body length of gravid females (4.88-5.33 mm) and a short spicule (66 µm long). The female specimen of Cucullanus sp. from Tilapia sparmanni Smith markedly differs from congeners parasitising inland fishes in Africa by the elongate pseudobuccal capsule and by the excretory pore far posterior to the oesophago-intestinal junction; apparently, it belongs to an undescribed species. Galeiceps larvae parasitising fishes are described for the first time. Cithariniella gonzalezi Van Waerebeke, Chabaud, Bain et Georges, 1988 is considered a junior synonym of C. khalili Petter, Vassiliadès et Troncy, 1972, and the previous records of Cithariniella citharini Khalil, 1964 from Synodontis spp. in Egypt concern, in fact, Cithariniella khalili Petter, Vassiliadès et Troncy, 1972. The specimens of Cithariniella reported by Koubková et al. (2010) from Paradistichodus dimidiatus (Pellegrin) in Senegal and misidentified as C. gonzalesi Van Waerebeke, Chabaud, Bain et Georges, 1988 are considered to represent a new species, C. koubkovae sp. n.; this is established by reference to the description and drawings provided by Koubková et al. (2010).

Distribution of Contracaecum (Nematoda: Anisakidae) larvae in freshwater fish from the northern regions of South Africa

A total of 1 847 fishes (16 species) from 14 reservoirs in northern and north-eastern regions of South Africa were collected and examined for larval Contracaecum spp. between 2005 and 2013. This study, the first to examine several potential second intermediate hosts, found Clarias gariepinus, Coptodon rendalli, Cyprinus carpio, Hydrocynus vittatus, Labeobarbus marequensis, Marcusenius macrolepidotus, Micropterus salmoides, Oreochromis mossambicus and Schilbe intermedius infected with the third-stage larvae. Coptodon rendalli, Marcusenius macrolepidotus and Micropterus salmoides are new host records for South Africa. A generalised linear model identified locality as the main factor affecting parasite burden.

Procamallanus (Procamallanus) spp. (Nematoda: Camallanidae) in fishes of the Okavango River, Botswana, including the description of P. (P.) pseudolaeviconchus n. sp. parasitic in Clarias spp. (Clariidae) from Botswana and Egypt.

Parasitological dissections of fishes from the Okavango River, Botswana, revealed the presence of nematodes of the subgenus Procamallanus (Procamallanus) Baylis, 1923 in five fish species belonging to three different families. Based on light and scanning electron microscopical examinations, they proved to represent one previously known and one new species, i.e. P. (P.) laeviconchus (Wedl, 1861) from Synodontis nigromaculatus Boulenger, S. thamalakanensis Fowler (new host) (both Mochokidae) and Schilbe intermedius Rüppel (new host) (Schilbeidae), and P. (P.) pseudolaeviconchus n. sp. from Clarias stappersi Boulenger and C. theodorae Weber (both Clariidae). Specimens of the new species previously collected from Clarias gariepinus (Burchell) (type-host) in Egypt were also examined. Both of these nematode species are very similar, differing from each other mainly in the shape of the circumoral flange, which is conspicuously lobed in P. laeviconchus and unlobed in P. pseudolaeviconchus. Previously, these two species have been confused in the literature under the name P. laeviconchus. A key to Procamallanus (Procamallanus) spp. parasitising freshwater fishes in Africa, including Madagascar, is provided.