M.Sc. (Zoology) / This study was undertaken to determine the osmotic regulation of Labeo capensis and to investigate the effectiveness of the addition of salt to water in which the fish are transported. The blood of L. capensis in tap water has a lower pH value than that of the same species acclimatized to salt water. It seems that the pH of fish transported in salt water is not altered immediately as in the case of fish transported in fresh water. In both groups the lowest pH values were reached two days after the fish had been transported ...

M.Sc. (Zoology) / Temperature plays a very important role in the metabolic environment of coldblooded animals such as fish. The primary objective of this study was to evaluate the quality of digestive processes and the importance of temperature in the digestive system of Labeo capensis. An important consideration in the choice of the experimental animal was the economic potential and widespread occurrence of Labeo capensis in the riversystems of the Transvaal. The experimental animals were kept at three different acclimation temperatures ( 14, 19 and 25 + 1°C) for a period of six weeks. An assessment of the influence of acclimation temperature on enzyme activity vas made using test kits supplied by BOERINGER-MANNHEIM. No information exists on the morphohistology of Labeo capensis and therefore investigation on the anatomy of the digestive system was carried out in this survey. The ventro-anterior mouth is ideally situated for bottom-feeding. Pharyngeal teeth and a pharyngeal pad (or palatal organ) is situated dorsally at the entrance to the oesophagus. A short oesophagus, which possesses both a supra- and infraoesophageal valve, exists. No stomach is present and the intestinal bulge affixes the intestine to the oesophagus. The exceptionally Iona intestinum proper lies coiled in the abdominal cavity. No rectum can be identified. The micro-anatomy of the intestinal proper and bulge differs minimally. The intestinal bulge possesses longer, slimmer villi in comparrison of the flat thickened villi of the intestine proper. The bulge lacks a longitudinal muscle layer. L. capensis cellulase and dicarrboxylase activty may be contributed to the intestinal microflora and/or foodstuffs present in the digestive system. Amylase possesses the highest and the proteases (trypsin and chymotrypsin) the lowest activity. The effect of acclimation temperature is most evident on amylase, and to a lesser extent on the phosphatases. Trypsin and chymotrypsin activity is less affected by acclimation temperature, although a distinctive loss of activity is recorded for both these enzymes. The loss of acid phosphatase activity is partially contributed to the rise in intestinal pH. The effect of reaction temperature was measured and recorded as AT-values.

M.Sc. / Please refer to full text to view abstract

M.Sc. (Zoology) / The Vaal River system is constantly subjected to pollution from various industrial, mining and agricultural activities. Consequently, pressure is continually exerted on the health of its fish communities and it was suspected that this may be a contributing factor to the repeated fish kills that have occurred in various sections of the river over the past few years. The aim of this study was to assess the health status of three fish species that were affected by the most recent mass fish mortality in the Vaal River. This was done using a combination of techniques including a histology-based health assessment (HHA) that involved a standard fish necropsy, the evaluation of blood parameters as well as a microscopic assessment of the liver, kidney, gills, and gonads. The histological results were semi-quantitatively assessed. Selected chemical substances were also tested for in water, sediment and the skeletal muscle tissue of the fish. Clarias gariepinus, Labeo capensis and Labeo umbratus specimens were collected from the Vaal River, approximately 2480m below the Vaal Dam (Latitude 26°51'17.47"S; Longitude 28° 7'16.58"E) following the latest occurrence of a fish kill in November 2011. Fish were collected using gill nets. Water was sampled in triplicate at three locations, and in situ measurements were done for selected physico-chemical parameters. Sediment samples were also collected and subjected to a sequential extraction technique and quantification of the heavy metals was done using Inductively Coupled Plasma-Mass Spectroscopy (ICP-MS). Metals in skeletal muscle tissue and water were quantified using the same technique. An analysis of variance (ANOVA), followed by the appropriate post-hoc test was performed to determine differences between means of variables i.e. morphometric, histological, substance concentration and blood parameters...