FIRST RECORD OF THE SNAKE CATFISH CLARIAS THEODORAE (WEBER, 1897) (CLARIIDAE: PISCES) FROM THE TRANSVAAL,SOUTH AFRICA

SUMMARY

Two new distributional records of the snake catfish Clarias theodorae (Clariidae: Pisces) from Transvaal tributaries of the Limpopo River are documented. This is also the first record of the snake catfish from the Transvaal. The habitat preference of this species is briefly discussed and brief comment is made on probable migration routes.     

THE SPECIFIC NAME OF THE SNAKE CATFISH,CLAXIAS THEOWRAE WEBER 1897

SUMMARY

Workers revising Southern African freshwater fishes have endeavoured to provide brief information on those persons who have had fish named after them. The provenance of all such patronyms in currently valid species has been established with one exception: Clarias theodorae M. Weber 1897. This was named after a niece of Professor Weber's wife, who accompanied him on his South African visit.     

First record of Chonopeltis inermis Thiele, 1900 (Crustacea: Branchiura) in the Limpopo River System with notes on its morphology

Specimens of Chonopeltis collected from the gill chambers of the snake catfish Clarias theodorae in the Luphephe River, a tributary of the Limpopo in northern Transvaal, showed close resemblance to C. inermis Thiele, 1900 previously only recorded from Lake Malawi. Comparative scanning electron microscopical studies on this material and specimens of C. inermis on loan from The Natural History Museum, London showed beyond doubt that C. inermis also occurs in the Limpopo System. This implies that it dispersed across a watershed and successfully established in a different water system.     

ASPECTS OF THE ECOLOGY OF KNERIA AURICULATA (PELLEGRIN, 1905) (PISCES: KNERIIDAE) FROM THE EASTERN TRANSVAAL SOUTH AFRICA

SUMMARY

Seven natural populations of Kneria auriculata occur in tributaries of the Crocodile River (Incomati System) on the eastern Transvaal escarpment. The routes it probably used to colonize these streams are discussed and used to explain its current restricted distribution with reference to its ecological requirements. Fish up to a fork length of 2,0 cm feed on invertebrates while larger fish utilize ‘Aufwuchs’, especially diatoms. This dietary difference results in an increase in the food spectrum and possibly also serves to limit competition between smaller and larger lengths groups. Relative gut lengths increase with an increase in fork length and this is correlated with a change in diet from invertebrates to diatoms. Observations on captive fishes indicated that adult fish are able to survive on a diet of Daphnia spp. The habitat of K. auriculata is considered to be unstable due to the occurrence of unpredictable summer floods in escarpment streams. As a result the species has a prolonged breeding season (October to April) while the presence of two size classes of ova indicate that it is a multiple spawner. This breeding strategy minimizes mortality in escarpment streams. The colonization by this fish of previously unsuitable and unavailable habitat indicates that it is a generalist. Its feeding habits and reproductive strategy indicate, however, that it has developed a certain degree of specialization in order to survive in a relatively unpredictable habitat. The conservation prospects of the seven natural and one translocated population varies from uncertain to good. Medium and long term conservation measures are needed to ensure the survival of this fish in the Transvaal.     

THE BARRED MINNOWS (TELEOSTEI: CYPRINIDAE) OF ZIMBABWE: IS THERE CAUSE FOR CONCERN?

Summary

Two species of barred minnow, Opsaridium zambezense and O. peringueyi, occur in Zimbabwe. The former is widely distributed in the Zambezi basin and some other rivers but is now absent from Lake Kariba and possibly some of its tributaries. The latter, which was only recently recognised as a distinct species and admitted to the Zimbabwean list, is much scarcer. It occurs in the Save and Limpopo catchments and there are only four specimens in the Natural History Museum of Zimbabwe collection. These specimens are all more than 40 years old and the lack of more recent ones suggest that O. peringueyi may be extinct, or close to extinction, in Zimbabwe. This situation may have come about through habitat alteration and drought, and emphasises the need for further monitoring of the current occurrence/distribution of fish species in the country.     

Evidence for lacustrine breeding by sanjika Opsaridium microcephalum (Teleostei: Cyprinidae) in Lake Malawi

Three species of Opsaridium occur in the Lake Malawi catchment. The kabyabya Opsaridium tweddleorum is a small species restricted to inflowing rivers and streams, the mpasa Opsaridium microlepis is a large lake-dwelling species that ascends the lower reaches of inflowing rivers during the rains to spawn, and the sanjika Opsaridium microcephalum has riverine, potamodromous and lake spawning populations. Evidence for sanjika spawning in the lake itself, rather than just in rivers, is presented here in the form of observations of courting behaviour by fully mature males and females on exposed rocky shores, together with the presence of pin-head fry in areas remote from any inflowing streams during the dry season.     

GOBIID FISHES OF THE GENUS GLOSSOGOBIUS IN THE LIMPOPO SYSTEM: A FIRST RECORD AND A RANGE EXTENSION OF G. CALLIDUS (SMITH, 1937)

Summary

Recently, a specimen of Glossogobius callidus was collected in the Marico Oog, a major source of the Limpopo River in the western Transvaal. This locality is some 1500 km from the river mouth. Earlier taxonomic confusion of Glossogobius giuris and G. callidus has resulted in the omission of G. callidus from identification keys published before 1979. As a result, that species has not been recorded from the Limpopo system. A previously published record of G. giuris from that system, at a locality about 950 km from the sea, is now shown to be based on a misidentification of G. callidus specimens.     

FIRST RECORD OF OREOCHROMIS MACROCHIR (BOULENGER, 1912) (PISCES:CICHLIDAE) FROM THE LIMPOPO RIVER IN SOUTHERN AFRICA.

Summary

During 1973/74, Barbus poechii, Oreochromis macrochir, O. andersonii, Serranochromis angusticeps, S. codringtonii, S. robustus and S. thumbergi from the Okavango System were introduced into the Shashe Dam (Limpopo System, Botswana). These species are alien to the Limpopo System. A fish survey during September 1991 disclosed the presence of two specimens of the greenhead tilapia O. macrochir in a large natural pool in the Limpopo River 7 tan downstream from the Shashe/Limpopo confluence. In August 1992 another specimen was caught in this pool. It is surmised that the likely origin of these specimens is the Shashe Dam. There is a possibility that the greenhead tilapia may interbreed with the indigenous Mocambique tilapia O. mossambicus. Consequently the genetic integrity of O. mossambicus in the Limpopo River may become suspect. If the other alien species introduced into the Shashe Dam reach the Limpopo River, O. andersonii may also interbreed with O. mossambicus while the Serranochromis spp. could be detrimental for feeding relationships in the Limpopo River and its tributaries. The impact that B. poechii could have is uncertain but it does not appear to co-exist with the closely related B. trimaculatus of the Limpopo System. Eradication of O. macrochir in the Limpopo River is not practical. Further stocking of the Shashe Dam as well as other impoundments in the Limpopo System with alien fish species should be discouraged.     

Ecological evaluation of local extinction: the case of two genera of endemic Mexican fish, Zoogoneticus and Skiffia

The Goodeidae is a family of endemic fish from central Mexico. Populations of several species are declining in the wild and two have been reported extinct; Skiffia francesae and Zoogoneticus tequila. Both species were native to just one locality in the Ameca basin. It is difficult to infer the causes of extinction, since limnological data from Teuchitlán prior to the extinction events are not available, and there are no replicate populations. As an alternative approach, we explored the potential links between key environmental variables and events of local extinction of any species in the two genera (four Skiffia spp. and two Zoogoneticus spp.). In 14 localities known to harbour populations of fish of at least one of the six focal species, we conducted limnological surveys in the rainy and in the dry season, and quantified population densities of endemic and introduced fish. In addition, we quantified the concentration of agricultural pollutants in water and mud samples taken from every locality in the dry season. We found that all the focal species face some conservation threat, but we also discovered an extremely small population of the reputedly extinct Zoogoneticus tequila; in contrast, Skiffia francesae was not found. Eutrophication and habitat fragmentation appear to be the main threats to the focal species, with habitat fragmentation exponentially reducing population size and driving populations into refuges where they face stochastic extinction.     

Migratory behaviour shapes spatial genetic structure of cyprinid fishes within the Lake Malawi catchment

• Genetic differences among freshwater fish populations are dependent on life‐history characteristics of the species, including the range of adult dispersal and the extent of homing to natal breeding grounds. However, the effects of variation in such characteristics on population genetic connectivity are rarely studied comparatively among closely related species.
• We studied population genetic structure within three congeneric cyprinid species from the Lake Malawi catchment that differ substantially in life‐history traits and conservation status, using a combination of microsatellite and mitochondrial DNA markers. Mpasa (Opsaridium microlepis) is a large (70 cm total length) migratory species that spawns in rivers, but as an adult is exclusively known from the main lake body. Sanjika (Opsaridium microcephalum), is a medium size (30 cm total length) species that exists in lake breeding, river‐lake migratory and apparently landlocked populations. Dwarf sanjika (Opsaridium tweddleorum) is a small non‐migratory species (15 cm total length) that persists in small tributaries surrounding the main lake and adjoining rivers.
• The results revealed striking differences among the three species in spatial genetic structuring. The river‐lake migratory mpasa showed only weak yet significant population genetic structure within the main Lake Malawi catchment, suggesting that there is no strong natal homing. The habitat‐generalist sanjika showed only weak spatial genetic differentiation at microsatellite loci within the Lake Malawi catchment, but moderate structure in mitochondrial DNA, potentially reflecting male‐biased dispersal. The river‐restricted dwarf sanjika showed strong genetic structure in both microsatellite and mitochondrial DNA, suggesting strictly limited dispersal at both adult and juvenile stages.
• We conclude that contrasting migration life histories have resulted in dramatically different patterns of population genetic structure among these congeneric species. The observed patterns demonstrate how divergent life‐history evolution may strongly influence broader patterns of population genetic connectivity in freshwater fish, with consequences for management and conservation. Specifically the results suggesting gene flow among Lake Malawi populations of mpasa, an IUCN red‐listed ‘Endangered’ species endemic to the lake catchment, imply that conservation initiatives operating at both local and catchment scales are needed to reverse local population decline.

     

Impact of Climate Change on the Relict Tropical Fish Fauna of Central Sahara: Threat for the Survival of Adrar Mountains Fishes,Mauritania

Background

Four central Sahara mountainous massifs provide habitats for relict populations of fish. In the Adrar of Mauritania all available data on the presence and distribution of fish come from pre-1960 surveys where five fish species were reported: Barbus pobeguini, Barbus macrops, Barbus mirei, Sarotherodon galilaeus, and Clarias anguillaris. Since 1970, drought has had a severe impact in the Adrar where rainfall decreased by 35%. To investigate whether the relict populations of fish have survived the continuing drought, a study was carried out from 2004 to 2008.

Methodology/Principal Findings

An inventory of perennial bodies of water was drawn up using a literature review and analysis of topographical and hydrological maps. Field surveys were carried out in order to locate the bodies of water described in the literature, identify the presence of fish, determine which species were present and estimate their abundance. The thirteen sites where the presence of fish was observed in the 1950s -Ksar Torchane, Ilij, Molomhar, Agueni, Tachot, Hamdoun, Terjit, Toungad, El Berbera, Timagazine, Dâyet el Mbârek, Dâyet et-Tefla, Nkedeï- were located and surveyed. The Ksar Torchane spring -type locality and the only known locality of B. mirei- has dried up at the height of the drought in 1984, and any fish populations have since become extinct there. The Timagazine, Dâyet el Mbârek and Dâyet et-Tefla pools have become ephemeral. The Hamdoun guelta appears to be highly endangered. The fish populations at the other sites remain unchanged. Four perennial pools which are home to populations of B. pobeguini are newly recorded.

Conclusion/Significance

The tropical relict fish populations of the Adrar mountains of Mauritania appear to be highly endangered. Of thirteen previously recorded populations, four have become extinct since the beginning of the drought period. New fish population extinctions may occur should low levels of annual rainfall be repeated.     

Genetic relationships between Marico barb (Barbus motebensis, Steindacher 1894), Redtail barb (B. gurneyi, Günther 1868) and Amatola barb (B. amatolicus, Skelton 1990)

Starch gel-electrophoresis was used to assess genetic differences between two populations of Barbus motebensis and two other taxonomic related and morphologically similar barb species. Ten of the 29 protein coding loci studied were polymorphic. In spite of the small bio-metric and meristic differences between the species studied, the extent of genetic differences suggests four distinct species. The evidence in support of a new barb species in the Ohrigstad River further adds to the current conservation importance of the rivers of the eastern Transvaal escarpment as a ‘hotspot’ for endemic fish species.     

FRESHWATER FISH OF THE ADDO ELEPHANT NATIONAL PARK

Summary

This study aimed to determine the distribution and relative abundance of freshwater fish in the Addo Elephant National Park. A total of 1578 fish specimens of 12 species were collected during surveys carried out in the Sundays River and four tributaries during 1996 and 1997. The redfin minnow Pseudobarbus afer comprised 81.6% of the total catch. Length frequency analysis of P. afer populations indicated recent successful recruitment in several rivers. Differences between rivers in the concentrations of dissolved and suspended solids and pH are possible reasons for different species complements. These surveys show the distribution of P. afer and Barbus aeneus in the Eastern Cape Province to be wider than previously reported. Management action is required to minimise opportunities for further establishment and spread of alien and translocated fish species and to conserve indigenous fish assemblages within the Park.     

Interactions between citrus psylla,Trioza erytreae (Hem. Triozidae), and spiders in an unsprayed citrus orchard in the transvaal lowveld

During a two year survey, a total of 3,054 spiders represented by 21 families were sampled in an unsprayed citrus orchard in the Transvaal Lowveld. Numerically the Salticidae was the dominant family (34.4%) followed by the Theridiidae (21.9%), Thomisidae (11.9%), Araneidae (7.9%), Clubionidae (7.0%) and the Tetragnathidae (3.7%). Eighteen species of spiders were observed to prey on citrus psylla,Trioza erytreae (Del Guercio) (Hemiptera: Triozidae), while six species trap nymphs and adults under their retreats and webs. There were significant positive correlations between the weekly psylla populations and the weekly populations of web-building spiders and wandering spiders present one to four weeks later but no significant correlation between the weekly spider populations and the weekly psylla populations present one to five weeks later. This seems to indicate that while spiders are unable to keep citrus psylla populations at acceptable low levels, they may contribute in reducing their numbers.      

Pfiesteria piscicida and Pfiesteria shumwayae in coastal waters of Long Island, New York, USA

Water and sediment samples were collected during summer and early fall 1999–2004 from coastal waters of New York State, USA, to test for the presence of Pfiesteria piscicida and Pfiesteria shumwayae. Physical and chemical conditions were characterized, and real-time polymerase chain reaction assays were conducted. Both species were relatively common and found at most sites at least once, and the frequency of positive assays was higher in sediments than in the water column. In a subset of the data from Suffolk County, Long Island, the presence of Pfiesteria was related to high chlorophyll a and relatively high nutrient concentrations. Partial SSU rDNA sequences of four PCR amplicons generated using P. shumwayae primers indicated two sequences: three were identical to GenBank P. shumwayae entries, but one showed enough sequence difference (15 positions in a 454 bp amplicon) to suggest a possible new species. Three isolates were tested for toxicity, and one was found to kill fish in bioassays. Despite the widespread presence of both Pfiesteria species and demonstration of potential to harm fish, no blooms of these dinoflagellates have been observed, nor has there been evidence of Pfiesteria-related fish or human health problems in these waters, likely related to colder temperatures than optimal for Pfiesteria species.     

Crustacean parasites of fishes in Lake Kariba,Zimbabwe, preliminary results

During a survey of fish ectoparasites in Lake Kariba (Zimbabwe), two crustaceans were often encountered. Dolops ranarum (Branchiura), parasite of the body, mouth and gill chamber, infected mostly cichlids, the catfish Clarias gariepinus, Synodontis zambezensis and two Mormyrids. Among cichlids clear host preferences were shown. No seasonal variations could be detected in the infections. D. ranarum parasitized predominantly fish above 15 cm in standard length. Lamproglena monodi (Copepoda) parasitized only the gills of cichlids with a preference for Serranochromis codringtonii, S. macrocephalus and Tilapia rendalli. Small fish were seldom infected. Seasonal variations of the prevalence occurred, the hot season being the less favourable. Few other crustaceans were found during the survey: a single specimen of Lamproglena hemprichii on the gills of the tigerfish, Hydrocynus vittatus; three specimens of Afrolernaea longicollis, one found on the gills of Hippopotamyrus discorhynchus and two on the gills of Mormyrops deliciosus; a hundred of Ergasilus mirabilis in a specimen of H. discorhynchus.     

BEHAVIOUR OF A RADIO-TAGGED TILAPIA RENDALLI BOULENGER IN LAKE NGEZI,ZIMBABWE

SUMMARY

The behaviour of a single specimen of Tilapia rendalli Boulenger was observed June through October 1986 in Lake Ngezi, Zimbabwe, by the use of a surgically-implanted radiotransmitter. The individual displayed a distinct homing response on two occasions, returning to the cove of capture (1) 1.5 km away within 48 hours of release (95Z of the distance was covered in 24 hours), and (2) after a lengthy migration some 6.0 km up the lake with other tilapia. During the only observed migration in late June, the fish travelled a conservative distance of 6.7 km over a 5-day period, sometimes at rates > 150 m/hr. The fish was also characterized by strong territoriality (i.e., preference to the cove of capture) and avoidance to the approach of the researcher by boat.     

Ichthyofaunal survey of rivers within Ewekoro cement manufacturing operational areas

A total of 298 fish specimens belonging to seven families were caught during ichthyoplanktonic survey of three rivers within the Ewekoro cement facility catchment area located in southwestern Nigeria. The highest numbers of specimens were caught from Alaguntan (37.0%) and Elebute (36.6%) rivers while 28.9% of the fish samples were collected from Itori River. The fish population and species diversity recorded in the catchment rivers were significantly lower (p < 0.05) than comparative catches from Ewekoro River located about 30 km downstream of the factory operational area. The food items ingested by the specimens across the seasons in the catchment rivers revealed obvious differences in diet with some degree of overlap in the fish trophic preferences. However, the omnivorous species dominated the catches in each of the rivers, irrespective of season. Categorization of the fish specimens based on habitat-related adaptive physiology showed that a significant number of the fish from Alaguntan and Itori Rivers have accessory respiratory organs. The four species with accessory respiratory organs were Polypterus senegalus Curv., Clarias gariepinus C. & V., Ctenopoma kingslayae Gun. and Channa obscura Smith. Of the 12 fish species recorded in the Ewekoro cement facility catchment rivers, only P. senegalus, C. gariepinus, C. obscura and Oreochromis niloticus (Trew.) are valuable food fishes in southwestern Nigeria.     

CLEANING BEHAVIOUR BETWEEN THE CICHLID FISH TILAPIA RENDALLI FENDALLI BOULENGER 1896 AND THE CYPRINID,LABEO CYLINDRICUS PETERS, 1852

SUMMARY

A case of interspecific cleaning behaviour is described between a cichlid host Tilapia rendalli rendalli and a Juvenile cyprinid Labeo cylindricus, in captivity. The host fish initiated the cleaning behaviour with a ‘head down’ display.     

Novelties in Adenia (Passifloraceae): Four new species, a new combination, a vegetative key, and diagnostic characters for known Madagascan species

Four new species and one new combination ofAdenia are presented, along with a vegetative key and diagnostic characters of the Madagascan species. Additional notes are provided about unusual specimens and field observations.Adenia kigogoensis from Tanzania is shown to be distinct fromA. stenodactyla (its putative closest relative) andA. digitata based on anther connation and other floral traits. The remaining new taxa are from Madagascar.Adenia litoralis has been observed from one coastal locality in northern Madagascar. It is distinctive in fruit size and leaf form.Adenia metamorpha is the only Madagascan taxon with a narrow cylindrical trunk and large napiform tuber; it is also known from only one locality in Madagascar in the Ankarana Reserve.Adenia mcdadiana is a robust liana with highly reduced glands and leaves that appear to be neotenic compared to its closest putative relative,A. sphaerocarpa. Finally, the position ofA. stylosa has been clarified. This species was once treated asA. firingalavensis var.stylosa, and prior to that asA. epigea var.stylosa, but molecular and morphological data suggest it is separate from these species.