M.Sc. (Zoology) / Please refer to full text to view abstract

Agricultural practices and increasing levels of pollution, water abstraction and numbers of predatory exotic fishes gave rise to mounting concern for the survival of the already endangered Twee River redfin, Barbus erubescens. Numbers were believed to be dwindling and an urgent re-assessment of the species' conservation status and major threats was called for. Distribution and estimated numbers of B. erubescens were detennined from a census conducted in the Twee River catclunent, and baseline knowledge of age and growth, reproduction, diet and habitat preferences was gained from biological work on collected specimens. Such understanding was necessary to formullate management ideas. Although an estimated 40% reduction in area of occupancy has occurred in the middle reaches of the Twee River system, the known distribution of B. erubescens was extended into the upper Suurvlei River. Despite fragmentation, surviving redfin populations remained healthy and total population size was estimated at 8400 individuals, 4100 of which were considered mature. Adults preferred pools with water exceeding 1 m in depth and tended to be associated with sandy or boulder substrates. Due to low numbers no such study was conducted on juveniles, although observations indicated a preference for the upper 50 cm of the water column, in or around marginal vegetation. Barbus erubescens spawn in summer and follow an asynchronous, iteroparous pattern. Males and females reach a maximum age of six years, maturing after two years at calculated SL of 45 mm in males and 42 mm in females. The diet was dominated by simulid and ephemeropteran larvae. Although the combined pressures of pesticide and fertiliser use, predation and competition from exotic species have undoubtedly had a negative impact on B. erubescens, the species has maintained viable populations. With continued expansion of these threats the focus of conservation attention may change but, at present, it is most likely agricultural water use, amounting to 7.43 x 10⁶ m³y⁻¹, 15% of the entire catchment production, which poses the greatest immediate threat to the survival of the species. Based on a deteriorating habitat and restricted area of occupancy, B. erubescens was rated Critically Endangered, and it is recommended that a conservation management plan be implemented in the Twee River catchment. The focus of such action should be on genetic preservation, with immediate projects including gamete cryopreservation and captive breeding and rearing programmes. Catchment management, including education and rehabilitation programmes, must be the long-term aim of conservation, to ensure the survival of B. erubescens.

Resumé: This study deals with the systematics and biogeography of a group of minnowlike Barbus species which, as adults, are characterized by bright red fins. The species are found in the coastal rivers of the fold belt region of the southern and south-western Cape Province. A closely related species, Oreodaimon quathlambae, inhabits certain high altitude streams of the Drakensberg mountains. Traditional methods were employed to revise the taxonomy of the species. Characters studied included morphometric and meristic measurements, and several qualitative anatomical features, several of which were studied in these species for the first time. A new species, Barbus erubescens Skelton, was described during the course of the study (Appendix 3). The taxonomic status of other species are endorsed or revised (B.afer and B.asper). Each species is redescribed and figured. The complete osteology of one redfin species, B.burchelli, is described and illustrated. Comparisons are made with all other redfin species and various osteological characters of systematic value are discussed. The phylogeny of the redfins is studied using Hennigian methods. Comparative data from other southern African Barbus species and pertinent literature were used to determine and evaluate synapomorphic characters and character sequences. The redfins sensu lato are shown to be diphyletic. Barbus calidus Barnard and B.erubescens were found to be sister species not closely related to the other redfin species. Oreodaimon quathlambae (Barnard) is shown to be monophyletic with the second redfin lineage. Barbus burgi Boulenger is placed as the plesiomorph sister species in this lineage and consecutive dichotomies derive Barbus burchelli (Smith); Barbus afer Peters, and Barbus asper Boulenger; Barbus phlegethon Barnard; Barbus tenuis Barnard and Oreodaimon quathlambae. The classification of the redfins is reviewed in the light of their phylogeny and recommendations for an infonnal hierarchy are made. The generic status of each lineage is considered and a new genus, Pseudobarbus, erected for all the redfin species except B.calidus and B.erubescens, but including O. quathlambae. The distributions of redfin species are recorded. A hypothesis is given to explain this distribution, based on a comparison of distribution patterns of a number of plant and animal species and a consideration of the geological and geographical history of southern Africa. Vicariance is suggested to be the major factor which influenced redfin distribution. A theory of dispersal explains the distribution of P.tenuis. The biogeography suggests the redfins are relatively ancient (possibly Miocene?) southern African fishes. Suggestions are made on future studies on the redfins. Attention is drawn to possible implications of the redfin study on systematic study of southern African freshwater fishes.

M.Sc. (Zoology) / Please refer to full text to view abstract

Ph.D. / A genetic study of seven fish species within the chubby and goldie barb groups of minnows was done by means of starch-gel electrophoresis. These two groups of minnows are widely distributed within the temperate rivers of southern Africa. Because of little morphological differentiation between the species within these two groups of barbs, their taxonomy has not yet been settled. Subsequently, species within these two groups of minnows could not always be identified with certainty and caused some problems for conservation bodies concerning the distribution and status of the different species. To make a contribution towards the taxonomy and conservation of these fish species, 330 specimens of goldie and chubbyhead barbs were analysed to determine the genetic variation within and between 17 populations comprising seven species. The heterozygosity values obtained in the present study within populations is similar to the values obtained for fish in other studies (Nevo et al., 1984; Alves and Coelho, 1994). The highest heterozygosity values were observed in fish populations collected from the eastern Cape, which could possibly be an indication of a relationship between this specific habitat and genetic diversity. In contrast, relatively low heterozygosity values were observed in some populations, for example Barbus brevipinnis (Marite River) and B. gurney! (Mgeni River), which could possibly be attributed to a degraded habitat. This assumption is supported by the fact that these populations were infested with parasites, which is often an indication of stress.

M.Sc. (Zoology) / Milt and blood samples of Aarbus aeneus were collected during November in order to perform chemical analyses of the blood and seminal plasma. Physical analyses were also carried out on milt. Throughout the year testes were collected in order to determine the stages of testicular development. This was done by means of histological analyses. The sperm counts averaged 8,41 x 10-3 cells rom while the spermatocrit value varied between 44% and 82% (average of 61,9%). All the milt samples collected were white in colour showing a high viscosity. Sperm motility gradually declined after activation and stopped after 82,5 seconds. Chemical values of the components tested in the blood plasma were statistically compared to those in the seminal plasma and no statistically significant differences were recorded between sodium, potassium, chloride, calcium, magnesium, glucose, total lipid, total proteien concentrations, osmolality and pH. The only component where a difference in concentration occured was fructose (30% probability). Sodium, calcium, magnesium, glucose, fructose, total lipid and total proteien concentrations in the blood plasma were significantly lower than the corresponding concentrations in the seminal plasma. In contrast the potassium concentration were higher in the seminal plasma. The pH of the seminal plasma (8,63) was alkaline while a pH of 7,5 was recorded for blood plasma. In the two lobe testis of Barbus aeneus semen is collected with seminiferous ducts into the vas deferens which together with the blood vessels are housed within a hilus. The testis is surrounded by a tunica albugenea and the seminiferous lobules are filled with cysts. The testis of the smallmouth yellowfish appears to be lobular and sperm are deposited into lumens which exist between the cysts. During the resting phase the interstitial tissue is very difficult to distinguish and is seen as a thin layer of cells between the lobules seperating them from one another...

The smallscale yellowfish (Labeobarbus polylepis, Cyprinidae), is a large yellowfish species restricted to the southern tributaries of the Limpopo, Incomati and Pongola river systems. This temperate species does not occur below altitudes of 600m and is restricted to perennial rivers with riffles/runs and deep pools. As with most yellowfish species in southern Africa this species is rapidly declining from its known localities. Because of the numerous dams and weirs in rivers, their breeding migrations are often restricted, and the associated flow regimes probably impact on the environmental cues that are a pre-requisite for successful reproduction. Little or no information is available on the breeding ecology of this species. There was thus the need to quantify reproduction requirements of Labeobarbus polylepis assisting aquatic scientists in ensuring flow requirements, conserving spawning habitats and preventing anthropogenic impacts that influence reproduction behaviour and environmental cues. During this study an in-depth investigation was done on the reproductive strategy of Labeobarbus polylepis. This included the habitat requirements, environmental cues associated with spawning, spawning behaviour and the artificial propagation of this species, as well as describing the early life history stages. From results obtained it is evident that this species spread its reproductive effort over a short period in the early summer season (October). A definite spawning behaviour pattern was observed during this study, which only occurred when environmental cues (daylight length, water temperature and constant low flow) coincides with optimal habitat requirements for spawning. Three definite stages were identified namely pre-spawning behaviour, spawning behaviour and post-spawning behaviour, that is described accordingly. From the observations made during natural spawning, as well as induced spawning, it appears that this previously thought multiple/ serial spawner is in fact a single event spawner. Also, the observed similarity between stream velocity, depth, substrate composition and layout of spawning beds suggest that this species is highly selective in terms of its habitat requirements for breeding. In the developing embryo, the relatively large periviteline space confirm that the eggs are also adapted to fast flowing waters in order to prevent the harmful effects of flow turbulence. Results of this study conclude that Labeobarbus polylepis is a highly specialised breeder that is sensitive to river regulation. / Prof. G.J. Steyn Prof. F.H. van der Bank

M.Sc. / The practice of catch-and-release (C&R) fishing has been widely promoted as a conservation strategy and fisheries management tool and is currently considered an ecologically sustainable practice. Factors negatively affecting fish as well as mortality have, however been shown to occur. The overall aims of this study were to determine the effect of C&R angling on tigerfish Hydrocynus vittatus and Vaal-Orange smallmouth yellowfish Labeobarbus aeneus by studying the physiological stress response as well as age, growth and reproductive characteristics. To determine the physiological response of tigerfish (n=63) and smallmouth yellowfish (n=96) data were collected during August/September 2008 (Okavango Delta) and from June 2008 through to December 2008 (Vaal River) for the respective species. Fish were collected using standard angling and fly-fishing techniques, anaesthetised in clove oil and blood drawn from the caudal veins; thereafter fish were weighed and measured, revived and released. To serve as controls, randomly selected fish (from each species) were kept for 72 h in pools filled with river water. Blood plasma was analysed for concentrations of glucose, cortisol and lactate to determine the effects of angling duration, fish size, and water temperature. In both species larger fish were shown to be angled for a longer duration compared to smaller fish. Levels of glucose, at times, were affected by water temperature (influenced by time of year). Plasma glucose concentrations in H. vittatus showed a slight increase whereas levels in L. aeneus decreased with greater angling durations. Few individuals from each species, (n=13 for H. vittatus and n=12 L. aeneus) showed significantly increased plasma cortisol concentrations. Lactate concentrations were found to increase significantly above control values in H. vittatus angled for < 1 min and L. aeneus angled for > 1 min. Increased handling durations of captured H. vittatus that had been angled for < 1 min showed a significant increase in plasma lactate concentrations. Results from the control fish indicated that baseline levels of lactate in H. vittatus and cortisol and lactate in L. aeneus were restored within 72 h of capture. The relative age of the selected species were determined with the aid of scales, lapillus otoliths (H. vittatus) and asteriscus otoliths (L. aeneus) The most appropriate methods found for ageing the two species were sectioned lapillus otoliths for H vittatus and whole asteriscus otoliths for L. aeneus. Males and females from both species were found throughout the age classes. Male and female H. vittatus had a longevity of 20 years and 16 years respectively, similarly, male and female L. aeneus had longevities of 19 years and 15 years respectively (relative age for both species). Summary 11 Hydrocynus vittatus males matured at a total length (TL) of 451mm and females matured at 522mm TL, corresponding to an approximate relative age of 4 years for both sexes. Labeobarbus aeneus males matured at a fork length (FL) of 289mm and females matured at 367mm FL, corresponding to relative ages of 4 and 6 years respectively. This is the first study of its type reporting on the physiological response of African freshwater game fish species as well as the first report of age determination of H vittatus in the Okavango Delta and the first for this species using otoliths. While the age of various L. aeneus populations have been studied this is the first time that otoliths are used in the Vaal River population. This study confirms that the physiological response, and potential negative effects of C&R are species specific, and that studies should be done on all targeted freshwater game fish species to ascertain the physiological stress imposed by C&R angling.

The biology of three large cyprinid fishes, Barbus holubi, B. kimberleyensis and Labeo capensis, was studied in a large turbid man-made lake on the Orange River, South Africa. The influence of environmental fluctuations on population dynamics was examined in relation to biological adaptations. On this basis inferences were made about the effect exploitation would have on the populations, and management alternatives were considered. Lake Ie Roux is situated in a semi- arid area, downstream from another large reservoir, Lake Verwoerd. In the pristine river, flooding is seasonal, and floodwaters carry a heavy silt load. Lake Verwoerd acts as a silt-trap and changes in turbidity in Lake Ie Roux (Secchi disc readings range from 15 to 160 cm) are influenced by hydrological management and are not necessarily seasonal. Water temperatures in the regulated river connecting the two lakes depend on the pattern of water release, and fluctuations in Iake levels depend on management practices. Reproduction was studied by examination of gonads and from the distribution of newly hatched juveniles. Age and growth was interpreted from the reading of scales and otoliths. Relative year class strength, dispersal and mortality were monitored using catch data from a regular, standardized gillnetting survey. The Barbus species spawn in the regulated river in spring or summer. Spawning is coordinated for a large part of the population and B. holubi spawn four to six weeks earlier than B. kimberleyensis. The juveniles are 'initially found along the shoreline, but later move into the pelagic zone and disperse throughout the lake. Year class strength is dependent on time of spawning and a late spawning results in a poor year class. For this reason, year class strength of B. kimberleyensis is generally poor, but there is a greater variation in year class strength of B. holubi, which is the dominant large Barbus. The two Barbus species exploit the pelagic zone, visually predating on zooplankton. When turbidity increases large scale mortalities occur, especially in B. holubi. Mortalities more than compensate for the reduction in carrying capacity, and the size of the reduced population may be inversely related to initial abundance. Growth rate is similarly affected by turbidity and density, and size at sexual maturity in B. holubi is reduced when growing conditions deteriorate. Labeo capensis do not form a homogenous population in Lake le Roux. Spawning occurs throughout the lake, but is erratic, probably depending on local rainfall. At each locality, more than one spawning may occur during spring and summer because of temporal variation in gonadal development. Juvenile survival appears to be mainly dependent on water level fluctuations, and strong year classes were formed when the lake was filling during the first two years. Subsequent year classes were weak. Subadult and adult B. capensis are herbivorous and depend on autochthonous production for food. They are relatively sedentary, but when turbidity increases fish smaller than 200 mm disperse, probably in response to food shortages. Mortality rates may be accelerated but mortalities are not as high as in B. holubi. The growth rate of B. capensis is variable and depends on turbidity and population density. Size at sexual maturity remained relatively constant during the study period. B. holubi has a relatively fixed reproduction cycle in Lake le Roux and exploitation is likely to dampen fluctuations in population density. Population growth and stability could be further promoted through hydrological management. B. kimberleyensis does not represent an exploitable population in Lake le Roux, although the large size obtained by this species (>3 kg) may be an attraction to anglers. B. capensis does not appear to have the potential to withstand sustained exploitation because of its erratic and generally poor reproductive success. However, the species is long-lived and can sustain relatively high densities under harsh conditions because of its relatively low mortality rates. It was concluded that harvesting of B. holubi must be flexible to promote maximum benefits to commercial and recreational fisheries, but B. capensis which is not an angling species, should chiefly be exploited when catches of B. holubi are poor, but left to recover in between. An alternative management strategy would be to commercially exploit the fish populations of several reservoirs. A monitoring programme could be established to decide when each reservoir is to be exploited to see to the interests of commercial and recreational fishing alike.

The southern African yellowfish (Barbus aeneus, B. capensls, B. kimberleyensis, B. natalensis and B. polylepis) are very similar, which limits the utility of traditional taxonomic methods. For this reason yellowfish similarities were explored using multivariate analysis and karyology. Meristic, morphometric and Truss (body shape) data were examined using multiple discriminant, principal component and cluster analyses. The morphological study disclosed that although the species were very similar two distinct groups occurred; B. aeneus-B. kimberleyensis and B. capensis-B. polylepis-B. natalensis. Karyology showed that the yellowfish were hexaploid, B. aeneus and B. kimberleyensis having 148 chromosomes while the other three species had 150 chromosomes. Because the karyotypes of the species were variable the fundamental number for each species was taken as the median value for ten spreads. Median fundamental numbers were B. aeneus = 196, B. natalensis = 200, B. kimberleyensis = 204, B. polylepis = 206 and B. capensis = 208. The lower chromosome number and higher fundamental number was considered the more apomorphic state for these species. Silver-staining of nucleoli showed that the yellowfish are probably undergoing the process of diploidization. Southern African Barbus and closely related species used for outgroup comparisons showed three levels of ploidy. The diploid species karyotyped were B.anoplus (2N=48), B. argenteus (2N=52), B. trimaculatus (2N=42-48), Labeo capensis (2N=48) and L. umbratus (2N=48); the tetraploid species were B. serra (2N=102), B. trevelyani (2N=±96), Pseudobarbus afer (2N=96) and P. burgi (2N=96); and the hexaploid species were B. marequensis (2N=130-150) and Varicorhinus nelspruitensis (2N=130-148). The taxonomic implications of polyploidy for the African cyprinids were considered, and its effect on species was discussed.