M.Sc. / Two yellowfish species, namely Labeobarbus aeneus and Labeobarbus kimberlyensis were collected in the Vaal Dam and Vaal River Barrage over two years. The macroscopic characteristics, such as dimension and weight were recorded prior to dissecting out the gills. The gills were examined using a stereomicroscope for Paradiplozoon sp., the number of parasites was recorded and they were flat-fixed and stored in 10% Neutral Buffered Formalin. Statistical analysis of host yellowfish dimension and weight, and Paradiplozoon sp. occurrence was performed using Statistical Processing Software Suite v.15.00. The seasonal variation in size and shape of adult life-stage Paradiplozoon sp. attachment clamp sclerites was investigated using the geometric morphometric software Morphologika2 v. 2.5. Water quality variables at the Vaal Dam and Vaal River Barrage were analyzed using RAU Water v.2 software to produce a final Aquatic Toxicity Index Solway aggregate score. Diporpa, juvenile and adult stages of Paradiplozoon sp. were collected from yellowfish in the Vaal Dam, and oncomiracidia were allowed to hatch from eggs that were maintained in vitro. Details of life-stages were examined and measured using light microscopy, epi-fluorescence microscopy, confocal laser scanning microscopy, and scanning electron microscopy. The Solway aggregate score indicated that the water quality score in the Vaal Dam was better than the Vaal River Barrage. The water quality score was the poorest at both sites in the summer and best during the winter. Turbidity was identified to be the poorest water quality variable. No Paradiplozoon specimens were recovered from the gills of fish from 2005 to 2007 in the Vaal River Barrage. The numbers of Paradiplozoon sp. on yellowfish in the Vaal Dam were the greatest in winter at 67% prevalence, when the water quality score was the best during the study. In contrast to the elevated diplozoid numbers in rivers of poorer water quality in Europe, a low number of Paradiplozoon sp. were collected in spring when the water quality was poorer. This may be attributed to the difference in the type of aquatic pollutant in the Vaal River and European rivers. Yellowfish were longest and heaviest during spring, followed by autumn, summer and winter. It was not possible to statistically prove whether the presence of Paradiplozoon sp. negatively influences the size and weight of yellowfish. The increase in weight is suggested to be as a result of increased fat reserves, prior to spawning in spring.

Fishes are widely used by biologist as ecological indicators that measure key elements of complex systems, without having to capture the full complexity of a specific system. The Vaal River in South Africa is classified as Africa’s hardest working river and is home to, two yellowfish species that are socially and economically important. Both these yellowfish species are considered to be sensitive to changes in water quantity and quality, habitat destruction and utilisation pressure and are often used as ecological indicators to manage aquatic ecosystems. Very little however, is known about their movement, response to changing environmental variables and interspecies habitat preferences. This study therefore aims to use radio telemetry as a method to characterise and evaluate how yellowfish behaviour is influenced by changing environmental variables. To characterise the behavioural ecology of the Vaal-Orange River yellowfish species in lentic and lotic ecosystems, Labeobarbus aeneus (n=18) and L. kimberleyensis (n=3) were fitted with externally attached radio transmitters in Boskop Dam (L. aeneus, n=4) and the Vaal River (L. aeneus, n=14) (L. kimberleyensis, n=3). Various methods were used to collect yellowfish species including: gill nets, to target mobile individuals, in deep habitats, electro-fishing (electro-narcosis) to collect yellowfish in shallow habitats and angling techniques in a wide variety of habitats. Thereafter yellowfish species were sedated and tagged with externally attached radio transmitters, before being released back into the system. Yellowfish were monitored for eleven months using a remote monitoring system together with manual monitoring surveys. Analyses of data collected showed that L. aeneus follows distinct behavioural patterns, with some individual variations in behaviour. Labeobarbus aeneus exhibited higher movement that are associated with deeper water during daylight hours (04:00-16:00). During nocturnal periods (20:00-04:00) L. aeneus showed a decrease in movement activity and preferred shallower water compared to daytime. However, L. aeneus in the Vaal River seems to be less influenced by bright daylight and this might be due to the turbidity of the river water. Labeobarbus aeneus in Boskop Dam showed higher movement counts during full moon phases whereas L. aeneus in the Vaal River showed higher movement counts during new moon phases. All tagged fishes in Boskop Dam and in the Vaal River preferred deeper water during full moon phases than during new moon phases. Movement were significantly higher (P<0.05) with increased temperatures and shallower water in summer whereas movement significantly decreased (P<0.05) with a decrease in temperature and increased depth in autumn and winter. Seasonal movement data were, however, limited. This study confirms that radio telemetry methods can be used to characterise the behavioural ecology of yellowfish species. In addition, the study has improved the knowledge of how environmental variables may affect the behaviour of yellowfish species. However, due to limited data and our understanding of these species, it is still uncertain how behaviour of yellowfish species can be applied as an ecological indicator of aquatic ecosystems. / Thesis (MSc (Zoology))--North-West University, Potchefstroom Campus, 2013

Fishes are widely used by biologist as ecological indicators that measure key elements of complex systems, without having to capture the full complexity of a specific system. The Vaal River in South Africa is classified as Africa’s hardest working river and is home to, two yellowfish species that are socially and economically important. Both these yellowfish species are considered to be sensitive to changes in water quantity and quality, habitat destruction and utilisation pressure and are often used as ecological indicators to manage aquatic ecosystems. Very little however, is known about their movement, response to changing environmental variables and interspecies habitat preferences. This study therefore aims to use radio telemetry as a method to characterise and evaluate how yellowfish behaviour is influenced by changing environmental variables. To characterise the behavioural ecology of the Vaal-Orange River yellowfish species in lentic and lotic ecosystems, Labeobarbus aeneus (n=18) and L. kimberleyensis (n=3) were fitted with externally attached radio transmitters in Boskop Dam (L. aeneus, n=4) and the Vaal River (L. aeneus, n=14) (L. kimberleyensis, n=3). Various methods were used to collect yellowfish species including: gill nets, to target mobile individuals, in deep habitats, electro-fishing (electro-narcosis) to collect yellowfish in shallow habitats and angling techniques in a wide variety of habitats. Thereafter yellowfish species were sedated and tagged with externally attached radio transmitters, before being released back into the system. Yellowfish were monitored for eleven months using a remote monitoring system together with manual monitoring surveys. Analyses of data collected showed that L. aeneus follows distinct behavioural patterns, with some individual variations in behaviour. Labeobarbus aeneus exhibited higher movement that are associated with deeper water during daylight hours (04:00-16:00). During nocturnal periods (20:00-04:00) L. aeneus showed a decrease in movement activity and preferred shallower water compared to daytime. However, L. aeneus in the Vaal River seems to be less influenced by bright daylight and this might be due to the turbidity of the river water. Labeobarbus aeneus in Boskop Dam showed higher movement counts during full moon phases whereas L. aeneus in the Vaal River showed higher movement counts during new moon phases. All tagged fishes in Boskop Dam and in the Vaal River preferred deeper water during full moon phases than during new moon phases. Movement were significantly higher (P<0.05) with increased temperatures and shallower water in summer whereas movement significantly decreased (P<0.05) with a decrease in temperature and increased depth in autumn and winter. Seasonal movement data were, however, limited. This study confirms that radio telemetry methods can be used to characterise the behavioural ecology of yellowfish species. In addition, the study has improved the knowledge of how environmental variables may affect the behaviour of yellowfish species. However, due to limited data and our understanding of these species, it is still uncertain how behaviour of yellowfish species can be applied as an ecological indicator of aquatic ecosystems. / Thesis (MSc (Zoology))--North-West University, Potchefstroom Campus, 2013

A large sportfishery that targets both smallmouth (Labeobarbus aeneus) and largemouth (Labeobarbus kimberleyensis) yellowfish exists in South Africa. Both species have high conservation priority, and no assessments documenting the effect of angling on L. aeneus and L. kimberleyensis have been undertaken. The overall aim of this study was to provide an assessment of the impact of angling on L. aeneus and L. kimberleyensis. The specific objectives of this study were to characterise the sectors utilising Lake Gariep, document catch, effort and total catch for the fishery as well as the locality specific biology of L. aeneus and L. kimberleyensis. The study was undertaken on Lake Gariep, South Africa's largest impoundment, situated on the Orange River system in central South Africa. Subsistence fishers were the dominant user group, constituting 60 % of the fishery, the remainder constituted recreational anglers. Angler catches were dominated by carp (Cyprinus carpio; 74 %), followed by mudfish (Labeo capensis; 13 %) and smallmouth yellowfish (8 %). Catches of largemouth yellowfish contributed < 0.5 % to the total catch. The relative abundance of species by weight differed by area (χ² test of independence: χ² = 182, df = 4, p ≤ 0.05). On any sampling day time fished was the best predictor for differences in probability of capture (PC) (Wald X²(1) = 7.169, p = 0.007). The probability of capturing L. aeneus differed significantly between month (Wald X²(5) = 20.690, p = 0.000) and region (Wald X²(3) = 46.755, p = 0.000). The single best predictor of differences in log abundance and non-zero CPUE was region (Factorial ANOVA p ≤ 0.05). Mean CPUE ranged from 0.21 ± 0.06 kg. man⁻¹.hr⁻¹ to 0.82 ± 0.11 kg. man⁻¹.hr⁻¹ in the OV region and 0.42 ± 0.10 kg. man⁻¹.hr⁻¹ to 1.17 ± 0.24 kg. man⁻¹.hr⁻¹ in the GD region. Angler effort was higher in OV than in GD and ranged from 17 ± 3 anglers/day to 45 ± 9 anglers/day and 6 ± 1 anglers/day to 41 ± 8 anglers/day, respectively. Total catch was higher in the GD 46.0 [95 % CI = 15:102.6] t. period⁻¹ than the OV region 40.0 [95 % CI = 13.9:89.6] t. period⁻¹. The total catch from the Lake Gariep fishery between March and December 2007 was estimated to be 86.0 [95 % CI = 40.4:154.8] t. period⁻¹. Age and growth was determined using whole otoliths. The growth of L. aeneus was best described by the von Bertalanffy growth model as Lt = 481.80 (1- e⁻°·²²⁽t⁺°·⁶¹⁾). Gonadal development for L. aeneus was seasonal, with the gonadosomatic index peaking in January, revealing a distinct spawning season. The length at 50 % maturity for female L. aeneus was attained at a fork length of 354.7 mm. Natural mortality (M) was estimated at 0.55 year⁻¹. The growth of L. kimberleyensis was described by the von Bertalanffy growth model as Lt = 763.22 (1- e⁻°·¹¹⁽t⁺°·⁶³⁾). Only 6 mature female and 15 mature male L. kimberleyensis were recorded during the study period. The smallest mature female was a 390 mm FL stage four female and the earliest recorded mature male was a 337 mm FL, ripe running male. Natural mortality (M) was estimated at 0.08 year⁻¹ for L. kimberleyensis. Per recruit analysis indicated that current fishing mortality reduces the L. aeneus spawner biomass by 7 %, which is considered negligible. Labeobarbus kimberleyensis forms an insignificant proportion of anglers catches and stock status is currently considered pristine.

M.Sc. (Aquatic Health) / Yellowfish and specifically Labeobarbus marequensis are a charismatic species targeted by anglers throughout South Africa. Their population are limited to the north-western parts of the country including the lower reaches of the Crocodile River that flows through the Kruger National Park (KNP). Despite conservation efforts the Crocodile River in the KNP is still highly impacted. The effect of these impacts on the ecosystem is largely unknown. The main aim of the study was to determine the influence of changing water quantity and quality in the Crocodile River on adult L. marequensis. This was achieved by evaluating altered flows (discharge) on the behaviour of adult L. marequensis in the Crocodile River using biotelemetry over a two year period. The influence of altered water quality was assessed using metal bioaccumulation as an indicator of metal exposure in L. marequensis, Clarias gariepinus and Hydrocynus vittatus in the Crocodile and Sabie Rivers during a high and low flow season. Biotelemetry was used on 16 L. marequensis and 12 H. vittatus to determine the habitat use and movement responses of the species. Fish were tagged with Advanced Telemetry Systems (ATS) and Wireless Wildlife (WW) tags and tracked remotely and manually. Home ranges were determined using Arc GIS ®, Habitat uses were analyzed using Windows Excel (© 2011, Microsoft inc.). Environment variables recorded were scored as primary and secondary and then combined with a weighting variable 2:1 ratio (primary variable: secondary variable). A mixed-model analysis of variance (ANOVA) approach with a random co-efficients model and Akaike’s information criteria (AIC) were used to test for significance. Analyses were conducted using SAS version 9 (SAS institute, Cary, NC)...