A pre-requisite for the formulation of a responsible fisheries management programme for an aquatic ecosystem is a comprehensive fish ecological study, which focuses on the various ecological and biological aspects of the fish population and related fisheries data. The fish ecological and fisheries data must be considered during the decision making process of management. The freshwater fish of the Eastern Caprivi, Namibia, has enormous value in terms of the local subsistence fishery. Fish is an affordable protein source in this region, and is of socioeconomic importance, as it generates income for up to 82% of the local households. Unfortunately commercialisation of the resource is becoming more and more prevalent in this region, as local commercial fishermen take advantage of the readily available fish resource, by the callous use of non-selective fishing gears such as drag nets. Unregulated fishing methods, such as the use of drag nets, is detrimental to the fish population and ecology of an aquatic ecosystem. The Ministry of Fisheries and Marine Resources (MFMR), Namibia, recognised the need for a fisheries management programme in the Eastern Caprivi region. Proper fisheries legislation, in terms of the recommended fishing gears which may be used by local fishermen, is however needed to achieve the goals set by such a management programme. The MFMR realised the need for a comprehensive fish ecological study in the Eastern Caprivi, which would thus aid in the formulation of legislation measures. Five, flood related, fish ecological surveys were consequently conducted in the Eastern Caprivi, between 1997 to 1999. The relevant ecological, biological, and fisheries data was gathered. This data will lay the basis for future studies in this region, and will aid management in their decision making process. Results derived from the experimental gill net data is of the most importance in the formulation of fisheries legislation. The data collected in the Eastern Caprivi was processed and the results presented and discussed in this study. Conclusions are made concerning the biological and ecological aspects of the fish species and the fish population. Recommendations, concerning the fisheries data, are made to the management of the Ministry of Fisheries and Marine Resources in aid of their legislation process. The Eastern Caprivi is a productive and intricate wetland system, consisting of rivers, floodplains, canals, lakes, swamps and marshlands. Three perennial rivers, the Zambezi, Chobe, and Kwando Rivers with their associated floodplains were studied. A total of 82 fish species occur in the Eastern Caprivi, of which 69 were recorded during this study / Prof. G.J. Steyn

D.Phil. / The results of this investigation suggested that fish hatcheries may cause a deterioration in water quality of thereceiving stream. With regards trout hatcheries, two sources of pollution were distinguished. These were tenned normal or continuous hatchery effluent and secondly dam cleaning effluent. The former effluent was of little pollution consequence. The bacterial analyses indicated that faecal bacterial concentrations were largely determined by the concentration of these bacteria already present in the influent water. However, hatcheries can result in an increase in faecal bacterial concentrations downstream. Biological growth potential investigations suggested that both normal effluents and dam cleaning effluents were only slightly enriched in comparison with the influent conditions. Metabolizable nutrient addition to the effluent water was considered to be of little importance. Although the hatchery effluent from trout hatcheries may result in marked disturbances in the aquatic macro-invertebrate fauna, the organism community structures indicated that severe organic pollution was not occurring. The communities of the macro-invertebrates had become almost normalized within 300 m of the hatchery outfalls'. The water chemistry analyses confirmed the biological findings. The suspended material from both trout and carp hatcheries was the most important contributor to pollution. Recommendations included the use of the existing chemical and physical standards of the Water Act of 1956, however that these should be supplement~d by other biological parameters. A distance of 1 km should exist between a trout hatchery and a farm boundary unless effluent treatment is undertaken. Carp dam effluent may have to be treated depending on the water quality of the receiving stream.

M.Sc. (Zoology) / The Limpopo Province covers an area of 12.46 million hectares and these accounts for 10.2 per cent of the total land area of the Republic of South Africa. The province is endowed with abundant agricultural resources and it is one of the country’s prime agricultural regions noted for the production of fruits and vegetables, cereals, tea, and sugar. A key feature of the agricultural industry of Limpopo Province is its dualism. There are two distinct types of agricultural production systems. The large scale commercial farming system occupies approximately 70% of the total land area. The smallholder farms are located mostly in the former homeland areas and they cover approximately 30% of the provincial land surface area. The town of Thohoyandou, with its surrounding villages, is the area of greatest human concentration in the Luvuvhu Catchment and subsistence farming is about a third of the total agricultural component. It is important to study the effects of agricultural inputs (e.g. fertilizers and sediment loads) on aquatic ecosystems in order to fully understand the processes involved of these stresses on aquatic ecosystems. Knowledge of these impacts toward the environment and human health is often limited due to lack of capacity building, especially among small scale farmers. Ten bio-monitoring sites were studied on five systems in the Vhembe district. The sites were sampled during the low flow period of November 2011 and the high flow period of April 2012. Sampling sites were selected to present conditions in the Mutale, Mutshindudi and Tshinane Rivers upstream and downstream of the potential influence of small scale agricultural activities...

Surface transient storage (STS) in stream ecosystems serve an important function in retaining nutrients and refugia for aquatic communities. Unfortunately, they can retain contaminants as well. Therefore, it is of importance to determine the residence time distribution (RTD). A RTD of a particular STS zone encompasses the time it takes for the first pulse of water to leave the STS zone, and for the mean residence time of water in that zone, among other things. The RTD of STS is also useful to subtract from the RTD of the total transient storage in streams in order to determine the hyporheic transient storage (HTS) of streams, which is difficult to measure. Currently, there is no definitive method of determining the RTD of STS. They have been determined with tracer injection alone, though this is time consuming and subject to interference from HTS. A relationship between STS physical characteristics and a RTD would be desirable, as this would characterize the time of entrainment of STS based upon a few easily measured physical parameters. This exists for groyne fields and flumes, which both have artificial STS. However, direct application of these equations to natural STS leads to errors due to simplistic geometries. The focus of this study determines RTDs in lateral STS, which is adjacent to the main channel of a stream and a significant proportion of STS, and its relationship to physically measurable parameters of lateral STS. Twenty sites throughout Oregon were each injected with NaCl to determine four residence timescales: Langmuir time (��[subscript L]), negative inverse slope of the normalized concentration curve of the primary gyre (��[subscript 1]), negative inverse slope of the normalized concentration curve of the entire STS zone (��[subscript 2]), and the mean residence time (��[subscript STS]). The RTDs of these sites were then compared to the length, width, and depth of each lateral STS zone, as well as the velocity of the adjacent main channel. This data also was used to calculate dimensionless parameters submergence, a measure of bed roughness, and k, a measure of exchange that relates ��STS to lateral STS and associated parameters. ��[subscript 1] was found to be identical to ��[subscript STS], and ��[subscript 2] could not be defined. ��[subscript STS] was found to be approximately 1.35 times ��[subscript L], the ratio of which (��[subscript L]/��[subscript STS]) is positively correlated with lateral STS submergence. ��[subscript L] and ��[subscript STS] are positively correlated with lateral STS parameters, and inversely correlated with main channel velocity. The value of k from this study was comparable to the value of k from other studies in flumes, and so there is a relationship between RTDs and lateral STS parameters. / Graduation date: 2013

Powdered laundry detergents are consumed in high volumes worldwide. Post use, they are directed toward water resources via wastewater treatment works or, as is the situation in many rural areas of South Africa, they enter the environment directly as a result of laundry washing activity undertaken alongside surface waters. Within wastewater treatment works, the main ingredient in powdered laundry detergents, the narcotic toxin linear alkylbenzene sulfonate (LAS), is mostly removed, rendering the waste stream a negligible risk to the aquatic biota of receiving waters. In contrast, the biological and ecological impacts of direct LAS input to the aquatic environment, as a consequence of near-stream laundry washing, are yet to be fully realised. Consequently, this thesis posed two research questions: 1) 'What are the LAS concentrations in a small rural South African river'? and 2) 'Is the in-stream biological community negatively affected at these concentrations?' The chosen study area, the community of Balfour in the Eastern Cape Province, is like many rural areas of South Africa where inadequate provision of piped water to homesteads necessitates laundry washing alongside the nearby Balfour River. The first research question was addressed in two ways: by predicting LAS concentrations in Balfour River water by assessing detergent consumption and laundry washing behaviour of residents living alongside the river; and measuring actual in- stream LAS concentrations on different days of the week and during different seasons. Results indicated that LAS concentrations were highly variable temporally and spatially. High peak concentrations of LAS occurred infrequently and were limited to the immediate vicinity of near-stream laundry washing activity with the highest measured concentration being 342 μg.L ⁻¹ and the average 21 μg.L ⁻¹ over the sampling period. The second research question was addressed by integrating the chemical evidence, determined from the first research question, with the biological evidence of stress responses measured in macroinvertebrates collected downstream of near-stream laundry washing activity on the Balfour River. Predicted and measured LAS exposure concentrations from the Balfour River were compared to a water quality guideline for LAS (304 μg.L ⁻¹), specifically derived in this thesis. Biological stress responses were measured at different levels of organisation: two sub-cellular responses (lipid peroxidation and cholinesterase activity); three measures of macroinvertebrate tolerance to water quality impairment; five measures of community composition; three measures of community richness; and a surrogate measure of ecosystem function (functional feeding groups). Weight-of-evidence methodology was utilised to assess, integrate and interpret the chemical and biological evidence, and at its conclusion, determined no effect on the in-stream biological community of the Balfour River downstream of laundry washing activity.