Includes bibliographical references (leaves 69-72). / Characteristics of extreme wave events along the coast of South Africa were researched through a dataset obtained by CSIR wave recording network at four locations. The locations from west to east are Slangkop, FA-Platform (Agulhas bank), East London and Richards Bay. The longest dataset available was the 25-year dataset at Slangkop measured by accelerometer wave buoys. In the subsequent years the wave recording network along the South African coast was expanded to six locations at present.

Variations in the global climate over time have long been associated with changes in the meridional overturning circulation of the oceans. It is now commonly believed that, during the Last Glacial Maximum (LGM), the transport of North Atlantic Deep Water (NADW) to the southeast Atlantic Ocean was reduced. A popular method to trace these ambient changes is the stable isotope systematics of neodymium (given as εNd). In this study εNd data were measured on mixed planktic and bulk foraminifera from two gravity cores, GeoB8336-6 and GeoB8342-6, retrieved from the Cape Basin at water depths of 3524 and 3521 meters from the western continental slope of South Africa. The samples were prepared following the protocol presented by the Cambridge group (Tachikawa, Piotrowski, & Bayon, 2014). Planktic and bulk foraminifera samples taken from the same core depth interval had the same εNd ratios within error, which suggests that bulk foraminifera may provide a quick way to reconstruct ambient bottom water values. However, more research is needed to further support these findings. While the Holocene samples' εNd ratios (εNd(N36/6a) -10.7±0.3 and εNd(N42/6a mean) -10.2±0.4) lie within the range of modern Eastern NADW (εNd(modern ENADW) -10.9±1.2), glacial samples yield significantly more radiogenic εNd ratios (εNd(N42/6b) -7.7/ εNd(N36/6b) -8.1). This indicates the greater influence of southern-sourced water masses and thus provides further evidence for a reduction of NADW during the last glacial. MIS3 samples show ratios that lie in between those observed in the LGM and Holocene, and it is hypothesized that ocean circulation during MIS3 was comparable to that during the transition from the LGM to the Holocene (Termination I).

Includes bibliographical references. / Coral δ¹⁸O and Sr/Ca records from massive corals in the western Indian Ocean (WIO) are used to establish the heterogeneous distribution of warming rates across the tropical and subtropical regions and to investigate if it corresponds with that from instrumental sea surface temperatures (SSTs). The coral records correlate with instrumental data better on monthly time scales compared to annual time scales. Coral thermal stress was assessed by the Degree Heating Months (DHM) technique and even though the coral DHM aligns quite well with instrumental DHM, the values from coral data are generally 2-3 times greater in magnitude than the DHM values from instrumental data. It was found that the accumulated thermal stress, calculated from coral and instrumental data, for the majority of the tropical and subtropical WIO sites has been increasing since the 1970’s. From 1870 to 1995, both the tropics and the subtropics have been warming in general, although with different and varying rates as recorded by the coral and the instrumental SSTs. It was further revealed that both the tropical and the subtropical WIO warmed during the summer and winter periods during 1870-1995. On longer time scales, the relationship between the coral records in the WIO and climate indices showed a significant interannual variability approximately centered at periods 3-6 years, indicating a probable link with ENSO and IOD. The extent to which coral reefs from different sites in the WIO are prepared to survive climate change based on historical SST variability and intensity of warming rates are described. It could therefore be suggested that some corals may be more favoured to survive warming climate compared to others because corals in the WIO are located in different oceanographic conditions and experience different climatic variations.

Recent research has shown that higher cognitive functions and learning occur in teleosts and elasmobranchs. Very little is known about the cognitive abilities of benthic sharks and no research has been published on the learning ability of the endemic Leopard catshark (Poroderma pantherinum) species of South Africa. This species is listed as data deficient on the IUCN red list and known threats due to anthropogenic impacts include fatalities because of bycatch and depredation in the small-scale commercial fishing industry. It has been suggested that sharks can be attracted to fishing boats through the sound of outboard motors and an association can be formed between the sound and easy prey on the hooks of fisherman. This pilot study examined the learning capacity of Leopard catsharks in Hermanus, South Africa, by using a series of food-reward tests based on instrumental conditioning. A target with black and white stripes was used as the discriminative stimulus, while an auditory cue acted as a bridging stimulus for the food-reward task. Sharks were collected by hand whilst diving and shore-angling in Hermanus from August 2015 to November 2015 and acclimatised before the onset of experiments. Four juvenile sharks were trained through operant conditioning using visual and auditory stimuli for ten days each, consisting of six trials per day. A fifth juvenile shark, acting as the control, was trained through the same method without the auditory stimulus to test the influence thereof on the learning rates of Leopard catsharks. This study showed that Leopard catsharks have the ability to associate a visual stimulus with a food reward through the aid of an auditory cue. The auditory cue was also shown to increase learning rates significantly as an association was formed between the presence of food in front of the target and the auditory signal. The individual sharks in this study displayed differing levels of stress and learning rates. It is suggested that even though Leopard catsharks show high diversity in learning rates and adaptation to stress, they possess the ability to learn and adapt rapidly to changing environments. The results possibly have important implications for the understanding of learning and conditioning in Leopard catsharks and the likely anthropogenic threats caused through learned behaviour in benthic sharks.

Temporal variability in infection of South African male sardines (Sardinops sagax) by a testicular coccidian parasite Eimeria sardinae was examined between putative western and southern stocks of this fish species. Samples were collected by commercial vessels from five localities; Gansbaai, St Helena Bay, Mosselbay, Port Alfred and Port Elizabeth (west and south coast) between 2012 and 2013. A total of 461 sardines were examined for the presence of Eimeria sardinae, including 185 males and 41 females from west coast and 180 males and 55 females from the south coast. Sardine females did not show any infection by the parasite. For males, prevalence of infection was 74.9% for the western stock and 76.5% for the southern stock. Mean infection intensity and standard error of the western stock was 6.7±0.7 and for the southern stock was 8.3±1.0. Parasite abundance and standard error of the western stock was 5.3±0.2 and 6.1±0.3 for the southern stock. A significant difference was observed within testes position (anterior, middle and posterior), with anterior being highly infected followed by middle and posterior (KW chi-square = 86.029, df = 2, p<0.05). Infection from the left and right testes did not show a significant difference (W= 623, p = 0.13). There was no significant difference in prevalence of infection, infection intensity index and abundance index per region across seasons. Seasonal pattern was the same in both stocks. There was a significant difference in monthly average GSI data of male sardines from west and south coast between 1996-2014 (KW = 5416.9, df = 11, p < 0.01). There was no significant difference between seasonal GSI and seasonal infection intensity index.

Bibliography: leaves 24-25. / The aims of this study are to analyse the extent and distribution of boat and shore based fishing along the Cape Peninsula for the purpose of designing a comprehensive fisheries monitoring program. The focus of this study is the non-quota regulated fisheries, which have thus far eluded monitoring attempts. A fishery monitoring program should be able to detect biologically significant shifts in resource abundance in the Marine Protected Areas and to provide data that are relevant to stock assessment models. Personnel and cost implications of the monitoring program will be estimated.

Includes abstract. / Includes bibliographical references (leaves 151-155). / The development and underlying physical connections of relationships between SWC rainfall and the Southern Annular Mode (SAM), South Atlantic sea surface temperature (SST), Antarctic sea ice concentration (SIC), and the EI Nino-Southern Oscillation (ENSO) were explored using spatial and temporal correlations. Insight gained from the correlation analysis was used to develop statistical forecast models for SWC seasonal rainfall, which served as an initial assessment of the potential for statistical seasonal forecasting of SWC rainfall.

Includes bibliographical references. / This study estimates rates of shark depredation in the charter boat fishery on Protea Banks, KwaZulu-Natal. Previous estimates based on fisher surveys suggested that shark depredation is a concern locally and may distort fishing mortality estimates. Methods involved quantitative data collection by an onboard observer from November 2013 to January 2014. Catch composition data were collected to enable comparisons with the commercial and recreational catch returns used in monitoring and assessment. Results revealed an average depredation rate of 8.4% that varied depending on the species fishers targeted. Depredation was highest when catching pelagic species (18.6%) and lowest when catching reef species (1.9%). Depredation rates were highest in November (19.6%) and lowest in January (5.3%). Observed rates were highest on the Banks itself and immediately offshore (9.9%), but no depredation was observed inshore of the Banks. The most commonly identified sharks involved in depredation incidents were the dusky shark (Carcharhinus obscurus) and the blacktip shark (Carcharhinus limbatus). Multi-dimensional scaling showed commercial catch composition to be significantly different from recreational and charter catch composition, mainly due to abundance of tuna in the recreational and charter sectors. No significant relationship was found between catch composition and shark depredation. Depredation is estimated to cost charter fishing operators 8% of their revenue. Depredation rates are at a level that could impact effective stock assessment and should be considered when making management decisions.

Numerous Argo floats (approximately 3800 floats) have been deployed in the world's oceans to gather hydrographic and biogeochemical data from the upper 2000 m. However, limited research has been done on the spatial and temporal distribution and potential sampling bias of Argo profiling floats brought on by the effects of bathymetric steering of currents, as well as oceanic features, such as meanders and eddies, that affect their distribution over the global ocean. This study investigates the sampling distribution of profiling floats and assesses the mechanisms that impact their trajectories and distribution in the Atlantic sector of the Southern Ocean. The study reveals that Argo floats are influenced and steered towards frontal jets, which in turn are steered by the underlying bathymetry. Argo floats have a 30 % higher probability of sampling regions where depths range from 4000 - 5000 m, rather than shallow regions of the oceans. Using bootstrapping, this result was shown to be statistically significant at the 95 % confidence interval. The sampling bias is associated with floats becoming entrained into deep reaching frontal jets that occur in the Southern Ocean and dominate the deeper waters. This is shown by analyzing the Argo float positions in relation to mean geostrophic currents which shows that there is a 40 % higher probability (statistically significant at the 95 % confidence level) of finding Argo floats in regions where geostrophic currents range from 0.1 - 0.22 m.s-1 even though the majority of surface currents in the Southern Ocean are found below 0.05 m.s-1. This indicates a non-uniform distribution of Argo floats in the Southern Ocean, which leads to a spatial sampling bias in the float data. This has implications for how we characterize the oceanography or understand the distribution and variability of oceanographic processes and its relation to climate.

ABSTRACT Spawning times and spawning intensity during the life cycles of some fish species found off South Africa and Norway were synthesized using data collected from the literature. The comparison of temporal patterns in spawning of South African fish species showed variable spawning times and intensity depending on the environmental conditions within that spawning habitat. Their spawning migration durations were suggested to be short since they inhabit a dynamic coastal upwelling ecosystem with intra-seasonal differences caused by changes in upwelling strength enhanced by south-easterly winds, nutrient-limited waters on the spawning grounds and stable thermal conditions. This contrasts with Norwegian fish species, which showed patterns of spawning times and durations that are restricted and confined to spring (February – May), probably due to strong, consistent seasonality, depending on primary production. This explains the inter-annual differences observed in their spawning periods, where strong south-westerly winds (downwelling), light intensity and salinity stratification could influence long spawning migrations. For Cape hakes, environmental variability influencing recruitment was further investigated on the west coast nursery grounds of the southern Benguela, particularly for deep-water Cape hake (Merluccius paradoxus). Biophysical characteristics of the west coast nursery grounds were assessed in relation to distribution of deep-water Cape hake juveniles (< 15 cm) using physical data (CTD, alongshore wind speed anomalies) and biological data (abundance/density of hake juveniles, recruitment estimates). Distinct spatial patterns of hake distribution were evident in relation to near-bottom environmental factors (temperature, salinity and oxygen). Nansen surveys conducted from 2003 – 2013 during summer (January – February) showed greater abundance of hake juveniles over the Orange Banks than in other nursery areas. The hake juveniles occurred in mid-shelf waters with oxygen depletion (2 – 3 mL O₂.L⁻¹) and hypoxic conditions (< 2 mL O₂.L⁻¹) and temperature ranges of 7 – 11 ⁰C. Salinity appeared to have less influence on hake juveniles' distribution. During spring surveys, hake catches were reduced on all nursery grounds except near Cape Columbine. There was a strong positive correlation between deep-water Cape hake recruitment indices and summer wind speed anomalies for the same year (Lag = 0 year) and with autumn wind speed anomalies of the previous year (Lag = 1 year). The relationship between winds and near-bottom oxygen concentrations on the Orange Banks is unclear and needs to be investigated.