Bycatch refers to the portion of the catch that is captured incidentally to the target species and is one of many growing problems facing the world's marine fisheries in recent years. Prawn trawling is one of the world's most lucrative marine fisheries, contributing about 3% to the total annual production of the world's marine fisheries. It is also one the most wasteful because it is associated with large quantities of bycatch. This is because of the high diversity and abundance of other organisms in areas where prawn trawling occurs, and the non-selective nature of the otter trawl used to land prawns. The South African shallow water prawn trawl fishery is typical of penaeid fisheries, and operates on the Tugela Bank off northern KwaZulu-Natal. The bycatch of penaeid prawn trawlers operating on the Tugela Bank was analysed between March 2003-July 2004 as a follow up to an initial study between May 1989-June 1992. The aim of this study was to determine if there has been any change in bycatch species composition over the 13-years and to determine the impacts of trawling on the environment. Catch composition data were recorded from 168 trawls processed onboard trawlers and on-shore. A total of 122 species was identified with teleosts contributing more than 60% to relative abundance by number. Comparison between the 1989-1992 and 2003-2004 data sets showed that although the species compositions were similar, there was an increase in the relative abundance of pelagic species. It is not clear if the change is due to trawling impacts or due to fluctuations in recruitment of these taxa. The annual discarded bycatch was estimated at 88 tonnes in 2003 and the prawn catch was estimated at 1 1 tonnes, both substantially lower than in 1 989-1992. There was no difference in discard rate between trawls from shallow and medium depths. However, there were significant differences in discard rates between large and medium gears, and warm (December-April) and cool (May- November) seasons. Kolmogorov-Smirnov tests revealed that there were significant differences between the 1990s and 2000s length frequency distributions of three sciaenid species (Otolithes ruber, Johnius dorsalis and J. fuscolineatus), which all showed an increase in fish size for the 2003- 2004 data. This assessment, however, is confounded by a gear effect as mesh size differs between the two sample periods. Based on the results of the study, management recommendations were made to improve the management of the Tugela Bank prawn trawl fishery by reducing bycatch. It was recommended that the observer programme continue for further investigation into the changes in species dynamics. Further research on BRDs (Bycatch Reducing Devices) and gear types that reduce bycatch is also recommended. / Thesis (M.A.)-University of KwaZulu-Natal, Durban, 2006

Coastal zone definitions are typically guided by the presence of absolute demarcations. As a result, the coastal zone becomes confined to, and identified as, an absolute space. This research challenges the ‘fixed’ nature of the coastal zone and suggests that there are a wide range of relational spaces that overlap and engage with each other to form the coastal space. These spaces and their sphere of influence extend beyond the ‘boundaries’ of what is legally defined as the coastal zone. Multiple coastal spaces have been identified based upon coastal stakeholder perceptions of what is relevant to the management of the coastal zone. Although there is a place for the absolute manner in which coastal zones are defined, definitions founded on absolute parameters tend not only to create a fixed abstract space, but they also naturalize a geographical construct to an unhelpful scale in terms of the functioning of coastal socio-economic and environmental systems. The absolute manner in which the coastal zone is defined and the reduced scale at which such a definition and the associated legislation is directed, severs and discounts, both temporarily and spatially, the influences of relational spaces that function at broader scales. The complication arises when the influences of such spaces are enmeshed within and beyond that legally defined coastal space. The legal definition and the associated legislation, in essence, attempts to address and solve issues occurring within the legal space, but disregards causative mechanisms that may lie outside of that legal space. This study suggests that a broader scaled and more holistic approach to defining the coastal zone, namely a system characterized by flows of interrelated spaces, will enable higher levels of sustainability to be achieved. / Thesis (M.Sc.)-University of KwaZulu-Natal, 2009.

Corals are able to source autotrophically-produced carbon since they have symbiotic unicellular dinoflagellates embedded in their tissue. However, they are also known to be heterotrophic feeders and able to ingest a variety of food sources, such as bacteria, particulate organic matter and zooplankton. Recent research has shown that heterotrophic feeding has a marked effect on both maintenance and growth in corals by providing mainly a nutritional source of nitrogen and phosphorus. Nevertheless, no study has yet been undertaken on the interactions between feeding and sexual reproduction in corals. This study examines the effects of heterotrophic feeding on the sexual reproduction of Pocillopora verrucosa in aquaria. Rotifers were used as live food source at two concentrations (LFC = low feed colonies) = 5×102 organisms/L; (HFC = high feed colonies) = 15×102 organisms /L) and an unfed control (UC = unfed colonies) was added for comparison. Three replicates of five colonies were used for each food concentration and control. Rotifers were distributed among the nine aquaria four times per week for three hours. Histological sections of coral polyps were prepared to monitor the development of gametogenic stages and the fecundity of the colonies. The number and size of oocyte, and spermary stages were determined in each polyp. Both fed and starved colonies proved to be simultaneous hermaphrodites and broadcast spawners. The gametogenesis period was short and occurred from October to December 2007. No spawning event was observed in the aquaria. However, the disappearance of mature oocytes in samples collected in January 2008 suggested that spawning took place between December 2007 and January 2008. Heterotrophic feeding had a strong effect on reproduction in P.verrucosa. The results showed that both the proportion of polyps with gametes and the reproductive effort were lower in the fed than in starved colonies. It is likely that an energetic trade-off occurred between reproduction and other metabolic functions. However, oocytes were bigger in fed corals compared with the unfed controls. Several hypotheses are proposed to explain these metabolic/energy distribution patterns. / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2009.

This dissertation focuses on both a hydrodynamic and geomorphological study of the Mgeni Estuary. Within the hydrodynamic study, the channel discharge, suspended sediment fluxes and estuary bed sediment characteristics and dynamics were established. Within the geomorphological study, cross-shore topographical surveying of the lower estuary region, measurement of slope angles and surface sediment characteristics were established. The results of this study illustrate strong seasonal variability. Maximum channel discharges, suspended sediment concentrations and fluxes occur during the summer months, as a result of large amounts of rainfall. Furthermore, maximum suspended sediment concentrations and fluxes occur during spring tides, as a result of a greater tidal range, which enhances bed sediment re-suspension via concomitant increased turbulence. Generally, maximum fluxes occur along the flood tide and ebb tide, during spring tides and neap tides, respectively, which suggest that the estuary is a sink for marine sediment during spring tides and an exporter of sediment during neap tides. The estuary bed sediments are very well sorted and predominantly classified as near-symmetrical, as a result of strong tidal currents that constantly transport and re-work the sediments. On average, the bed sediments are medium sand and in all probability are largely derived from the marine environment. Estuary bed sediments contain negligible mud and organic contents, which as research suggests, is common in such highenergy estuary mouths. Apart from the seasonal variability, the survey profiles and surface sediments illustrate alongshore and cross-shore variations. The profiles become flatter and finer from the Beachwood Mangroves section of the barrier towards the estuary mouth in the south, as a result of sheltering due to the engineered groyne, conforming to Bascom (1959) and Komar’s (1998) sheltered and exposed coasts concept. The survey profiles conform to the summer and winter profiles put forward by Dardis and Grindley (1988). The winter profiles consist of higher, distinct berms and berm crests, as well as vertical erosional faces, whilst the summer profiles are lower, flatter, and consist of unclear berms and berm crests. Sediments are coarsest along the lagoonward slope and finest within the estuary. A strong, positive correlation was generated between slope angle and mean grain size. Despite the low organic contents, the estuary sediments consist of the highest values of organic matter, with the beach and barrier sediments displaying negligible amounts. Thus, the Mgeni can be classified as a very dynamic and active zone. / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2009.

The aim of this review is to gave a detailed overview of the status of aquaculture in the Western Indian Ocean Region. Emphasis is based on the legislation, cultured species and candidate species for aquaculture. The review also describes the most recommended species for aquaculture in the region in terms of biology, environmental constraints and factors that inhibit a successful growth. This review covers the Western Indian Ocean (WIO) countries: South Africa, Mozambique, Tanzania, Kenya. Madagascar, Mauritius and Seychelles. Different sources of information are used such as annual reports of each country from Food and Agriculture Organisation (FAO). governmental reports, counties profiles available m the internet. Extensive and semi-intensive aquaculture systems are the most practiced in the WIO countries. Little information is available regarding the environmental impacts associated with aquaculture. The region presents a good potential for developing mariculture. although manculture activities are not yet developed and cannot satisfy the local and international demand for aquatic products. South Africa presents a noticeable development in rearing abalone Haliori: midae while Madagascar and Mozambique the marine shnmp Penaeus monodon. P monodon is the main species reared in the WIO region. Marine species are the most recommended for the region, as opposed to freshwater species, due to the vast coastline. Generally, improvements in the current legislation relating to aquaculture are needed in most of the WIO countries. Mozambique and Madagascar present significant progress in the development of legal framework relating to aquaculture; however, similar efforts have been seen in all countries evaluated. The results of the SWOT (Strengths, Weakness. Opportunities, and Threats) analyses show that the major strength presented by the region is the availability of suitable areas for the aquaculture development. The main strengths regarding aquaculture are the availability of good water quality and Government commitment in developing the sector. The WIO region presents good opportunity to improve the coordination between institutions, avoiding duplications m the process of application for permits. The weaknesses are related mostly to the lack of aquaculture development plans and. although many countries have come as far as drafting such plans, the implementation thereof is still low. The review provides an overview of the current status of aquaculture in the WIO region as well as provides re commendations for best aquaculture pracnces and species that are economically and ecologically suitable. Recommendations are made based on the SWOT analyses for the individual WTO countries from well established aquaculture practicing countries. / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2011.

The study area, the KwaZulu-Natal Bight, is an oceanographically important area, which, regardless of having two of the most important fisheries off the east coast of South Africa, has received little research attention regarding its biological functioning. Until now chiefly oceanographic processes have been considered the drivers of this generally oligotrophic system. This study seeks to understand which of three important processes, a topographically induced oceanic upwelling cell near Richards Bay, a cyclonic eddy near Durban, or fluvial fluxes centred around the Thukela River, forces ecological functioning through their nutrient or organic matter input. The overall aim of the thesis is to understand the pelagic and benthic ecosystems of the Bight in terms of these drivers through the use of stable isotope (δ¹³C and δ¹⁵N) analyses of a range of biotic and abiotic samples. These were collected on board of a number of research cruises – forming predominantly part of the larger African Coelacanth Ecosystem Programme suite of studies – in the wet and dry seasons of 2010. Isotopic analyses found distinctions between fluvial and oceanic particulate organic matter and indicate that upwelling was not occurring in either sampling season. Organic matter originating from the Thukela River did not play a significant role in the wet season, although it dominated the planktonic pelagic food web in the dry season. The organic matter of the most productive region in the Bight, the Middle Shelf, was of riverine origin in the dry season, but of indeterminate origin in the wet season when it may have been an artefact of an old upwelling event which had previously occurred to the north of the Bight. There is, however, some evidence suggesting that this organic matter may rather have been of riverine origin, with its δ¹³C signals subsequently having been modified by the diatom bloom occurring there. In the demersal ecosystem, sediment isotopic data show organic matter to be well-mixed throughout the Bight in both seasons, with riverine organic matter dominating most of the Bight except its northern and southern edges, where oceanic organic matter increases in importance. Sediment organic matter (most likely via the macrobenthic biota) was deemed an important food source for demersal animals and omnivory an important feeding strategy. Seasonal studies from 2008 to 2010 in the Thukela Bank area indicate that the demersal animals' stable isotope signatures responded to the seasonal isotopic changes in riverine organic matter, indicating the cross-seasonal importance of this food source to the demersal ecosystem. Parallel methodological studies examined how routine isotopic sample handling procedures could have affected the results of the ecological studies. These studies suggest that i) effects of preservation/fixation methods and the use of dyes are species-dependant; ii) acidification has no effect on zooplankton isotopic signatures, and that iii) drying methods alone and interactively with multiple thawing and refreezing of samples affect the stable isotope values offish muscle tissues. Recommendations are made for further improvements in methodology and considerations to be taken when processing samples. Overall, it is concluded that riverine input to the Bight has a more important biological role than previously thought, and that organic matter from this source is an important driver of ecosystems within the Bight throughout the year for the demersal and pelagic ecosystems. / Thesis (Ph.D.)-University of KwaZulu-Natal, Westville, 2012.

The Port of Durban, with its close proximity to industrial, urban and agricultural activities, receives a number of chemical pollutants that settle out and accumulate in sediments. Chemical analysis of these sediments has indicated elevated levels of chemicals that, according to sediment quality guidelines, might cause adverse biological effects. However, elevated concentrations alone do not necessarily imply that chemicals are present in bioavailable concentrations high enough to be harmful to organisms that come into contact with them. Thus, chemical tests alone cannot provide an accurate indication of the potential adverse biological effects of these chemicals. In this regard, toxicity tests of sediment porewaters have been developed using sea urchin gametes to assist in determining the bioavailability of chemicals present in porewaters. Further, procedures such as Toxicity Identification and Evaluation (TIE), which involves the manipulation and/or treatment of toxic porewater, have also been developed to assist in the isolation and identification of chemicals causing porewater toxicity. In this research, on a number of sampling occasions between July 2007 and July 2009, three replicate sediment samples were extracted from a site in the Port of Durban known to contain sediment with potentially toxic porewater. Results of initial toxicity tests, using the sea urchin fertilisation test indicated the presence of toxic porewater although, in some instances, porewater toxicity was highly variable between replicate samples. However, results from TIE procedures performed to reduce potentially toxic concentrations of metals, ammonia and organic compounds did not resolve the primary cause of porewater toxicity. Further research indicated that chemicals including hydrogen sulphide, which can occur naturally in organically enriched sediments, may have been confounding factors that masked the potential toxicity of other chemicals present in the sediment samples. Consequently, a sampling strategy and modified TIE procedure have been recommended. The sampling strategy has been designed to assist with detecting and understanding any sample variability that may occur. The modified TIE procedure, which suggests initial procedures to determine and reduce/remove the possible confounding effects of potential naturally occurring compounds such as hydrogen sulphide from the porewater, could be used in future to understand and evaluate the quality of contaminated sediments from similar environments. / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2011.

A high proportion of South Africa’s temporarily open/closed estuaries (TOCEs) occur along the coast of KwaZulu-Natal. Mouth breaching events have major impacts on the biological processes of an estuary, resulting in depletion of zooplankton via flushing and sediment scouring. Mouth closure, usually within weeks of a breaching event, initiates a new phase of stable physical conditions, leading to biological recovery. Therefore, the aim of this investigation was: (1) to monitor the recovery of zooplankton abundance and biomass following a breaching event in the Mdloti Estuary; (2) to compare the spatial and temporal patterns in zooplankton distribution in the lower (mouth), middle and upper reaches (head) of the Mdloti Estuary in terms of abundance and biomass just before, during and after a mouth breaching event; and (3) to determine the key environmental variables influencing zooplankton abundance and biomass during such a breaching event. The zooplankton community of the Mdloti Estuary was studied over a 3-month period (27 January to 26 April 2004). The estuary was artificially breached on 12 February 2004, due to a fish kill, and closed again naturally on 18 March 2004. Samples were collected twice a week in the lower, middle and upper reaches using a WP-2 net and an epibenthic sled. Upon breaching, 98% of zooplankton biomass was lost through sediment scouring and flushing. During the open phase, zooplankton biomass showed a temporary recovery, but due to continual sediment scouring and flushing, this was not sustained. One-way ANOVA revealed a significant difference in total zooplankton abundance and biomass between phases (d.f.2, 59 = 55.0; p < 0.001; d.f.2, 59 = 15.51; p < 0.001). ANCOVA revealed significant differences between zooplankton abundance and biomass (d.f.0.05;2,56=2.97, p = 0.05) at the different estuarine reaches (d.f.0.05;2,56=5.51, p < 0.01) . In both cases, the lower reaches recovered quicker than the middle and upper reaches. Thirty-five taxa were identified during the study, with only 10 contributing more than 1% of the total abundance or biomass. For the overall study, P. hessei was the dominant species, accounting for 42% of the total abundance and 58% of the total biomass. Keratella sp. 1 accounted for 17% and 11% of the total abundance and total biomass, respectively, while harpacticoid copepodites and Acartia natalensis contributed 11% and 10% to the total zooplankton abundance and 3% and 7% to the total zooplankton biomass, respectively. Pre-breaching levels of zooplankton were reached only 9 days after the closure of the mouth, during the recovery phase (mean 1.1 x 105 ± 6.5 x 104 SD ind.m3 and 2.4 x 102 ± 1.6 x 102 SD mg.m3). Zooplankton abundance and biomass reached a peak in the lower reaches after 19 days, in the upper reaches after 28 days and in the middle reaches after 35 days. The zooplankton biomass decreased slightly, but stabilised for the duration of the study. During the study the state of the mouth was primarily responsible for regulating the zooplankton abundance and biomass. However, the zooplankton in the different reaches did not recover in synchrony after mouth re-closure because abiotic factors and food availability were different in the three estuarine reaches. / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2010.

Estuaries are complex ecosystems, typified by remarkable fluctuations in environmental conditions. In addition to this natural variability, stochastic events and anthropogenic influences effect change at different spatial and temporal scales. Macrozoobenthic invertebrates are preferable biological indicators because of their sensitivity to variations in habitat quality. This thesis describes inherent changes in the macrozoobenthos of temporarily open/closed estuaries (TOCEs) in KwaZulu-Natal, ‘change’ as measured in spatial and temporal community differences using various community metrics, namely species composition, abundance and diversity. Standard and widely published quantitative sampling techniques were employed, with simultaneous measurements of ambient physico-chemical conditions, including sediment characteristics. The thesis is in three parts. Regional distributions and long-term decadal-type changes in macrozoobenthic community structure were determined for 31 TOCEs using historical data (1998/9) compared with more recently collected data (2009/10). Results showed that, although of the same estuary type, the macrozoobenthic communities of these estuaries differed significantly. Furthermore, community composition did not reflect a north to south progression of predominantly tropical species to predominantly warm-temperate species. In the last decade, the macrozoobenthos of these systems had indeed changed (in composition, abundance and/or diversity), the scale of change within each estuary being estuary-dependent. The recolonisation of two urban and non-urban estuaries by macrozoobenthos following a stochastic flood disturbance was investigated, describing the short-term community changes during the recovery process. Differential recolonisation patterns were attributed to inherent differences in community composition and not to the influence of urbanisation. Recolonisation was marked by distinct changes in community structure, with the recovery trajectory being interrupted by localised disturbances (e.g. change of mouth state). Species indicative of the observed spatial and temporal community changes were examined for similarities in habitat association and trophic characteristics. The species that were representative of these KwaZulu-Natal TOCEs were identified and included common and highly abundant generalists of varying trophic groups. In conclusion, the present findings illustrated the effectiveness of using macrozoobenthic communities to depict ‘change’ over multiple temporal and spatial scales. This also supports their usefulness as a study group in environmental monitoring and detecting the loss of ecological functioning and biodiversity in estuaries in the long- and short-term. / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2011.

Estuaries, the interface of interaction of fluvial discharge and marine action serve as temporary repositories of materials (solid and dissolved) before finally exporting them to sea. This interchange of material is dependent on a range of factors such as tidal range, prism, and symmetry; fluvial flows and estuarine morphodynamics. The efficacy of transfer of materials to the marine environment is important for estuarine health particularly in estuaries located in highly developed areas such as the major coastal metropolitan areas of many countries. This study assesses the efficacy of the export of nitrates from three estuaries of the eThekwini Municipality of the city of Durban, South Africa which maintain an open mouth status, ensuring tidal exchange throughout the year. The focus of this study was to determine and analyze the net flux of nitrates between the Isipingo, Mgeni, and Tongati estuaries of the eThekwini Municipality, and their adjacent nearshore environments. It questioned whether the Isipingo, Mgeni, and Tongati estuaries were efficient at exporting nitrates to their adjacent marine environments. The abovementioned estuaries are classified as temporarily open/closed estuaries, and were chosen for this study, as they maintain an open mouth status for most of the year. An open mouth condition was critical in order to conduct this study, as tidal exchange, and the resulting nitrate fluxes, could occur. The net flux of nitrates was measured for these estuaries on a seasonal basis for both spring and neap tides. Measurements were taken over the tidal cycle, ensuring that the peak high and low tides were sampled. To determine the values of net flux, the cross-sectional area of the estuary mouths were measured; average flow velocities of water were measured; and average concentrations of nitrates were obtained. Results indicate that although there is a net export of nitrates to the nearshore environment, there were instances, particularly on the spring tide, when a net import of nitrates into the estuary occurred. The origin of the latter is likely derived from nearshore upwelling; unusually high biotic decomposition at sea and/or the longshore drift transport of decomposing sewage outfall. This creates an added dimension for consideration in estuarine management plans. Taking all three estuaries studied into consideration, a net export of nitrates for all seasons for the eThekwini Municipality was measured with a clear seasonal influence detected where high rainfall seasons led to greater export as a consequence of greater fluvial flows, erosion and leaching of agricultural lands and longer ebb duration. / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2011.