This study focuses on several aspects of the life history of R. globiceps, and includes a study of juvenile habitat, a hatch date analysis, methods to increase precision of age estimates obtained from reading otoliths and a per-recruit assessment.

Includes bibliographical references. / Habitat fragmentation is recognized as a primary cause of biodiversity loss. To maximize biodiversity maintenance, researchers in the field of conservation biology often investigate population demography and genetic variability for species inhabiting fragmented landscapes. Findings from such work enable effective conservation management, maximizing viability for potentially imperiled populations. Previous research has relied predominately on spatial analysis when investigating population demography and genetic variability; however, temporal analysis is also important to species conservation. As of 2006, reptiles and amphibians had the highest threat status among small, terrestrial vertebrates, warranting continual investigation of herpetofaunal species inhabiting fragmented landscapes. Of the two, reptiles are the more poorly studied, though are suggested to be equally or more threatened than amphibians. The Cape Dwarf Chameleon, Bradypodion pumilum, exemplifies one potentially threatened reptile species which has suffered habitat loss, due to urbanization, inducing fragmentation and transformation among much of its habitat. As a result, many B. pumilum populations currently exist as a collection of isolated groups inhabiting critically endangered ecosystems.

Includes abstract. / Includes bibliographical references. / The study site for this thesis is Sodwana Bay, focus of the African Coelacanth Ecosystem Programme, a multidisciplinary project centered on understanding the Coelacanth habitat of Sodwana Bay at an ecosystem level. Globally and locally, the biodiversity of small species is under-studied. While historically, research in Sodwana Bay has focused on larger, more conspicuous species, this study records for the first time macroinvertebrate communities in Sodwana Bay. Macroalgal biotopes were selected to focus sampling. Macroinvertebrates, macrophytes and sediment were collected from forty-five 25 x 25 cm quadrats.

Includes bibliographical references. / The brooding behaviour and brooded young are described for Ophioderma wahlbergii Müller & Troschel 1842, a large, common brittle star from the coastal waters of South Africa. Twenty specimens were collected each month from June 2013 – May 2014 (n = 240). The species was found to be gonochoric.

Bibliography: pages 75-84. / Isotope assessments of foodweb relationships amongst pelagic organisms may be influenced by their lipid content, since lipids are more depleted in ¹³C than other biochemical compounds. This is particularly important for plankton which show a greater decrease in δ¹³C caused by the failure to remove lipids during sample preparation, than the muscle tissue of pelagic fish species. Lipid removal is important for those fish species whose lipid content and magnitude of diet-consumer fractionation are simultaneously related to their size. The period required for pelagic fish to isotopically reflect a new diet is slow, of the order of months and years, and may depend on the diet and the magnitude of isotopic change displayed. It is likely that this rate decreases as the fish approach isotopic equilibrium with the new food source.

Bibliography: pages 106-117. / The construction of a nuclear power station on the west coast of South Africa will result in a large volume of heated effluent being discharged into the ocean, thus raising the temperature of the surrounding sea by a few degrees. The physiological effect that this hot water will have on three species of crab common along the west coast, is presented in this paper. Parameters of the energy equation C = Pg + R + Uₑₓ + F + Uₑ have been measured for adult Plagusia chabrus, Hymenosoma orbiculare and Cyclograpsus punctatus. It appears that rate-temperature responses increase with increase in temperature for all three species. Favourable water temperatures were found to be between 16°C and 21°C for the three species, with temperatures of 26°C being detrimental, especially during moulting in P. chabrus and H. orbiculare. The energy budget and energetic efficiencies are calculated for all the species and it appears that the increased temperatures around Koeberg Power Station will be beneficial to the adult crab species.

Bibliography: leaves 95-104. / Beetles pollinate over 80% of all flowering plants and feed on the two most common floral rewards, nectar and pollen. Pollen is nutritionally very valuable, being a rich protein and carbohydrate source. However, the hard and highly resistant outer wall (exine) of the grain is an obstacle that pollen-feeders must overcome in order to benefit from the pollen's nutritious protoplasm. There are a variety of mechanisms that pollen-feeders may use to deal with the exine. Collembolans secrete exinase that breaks down the wall, but other pollen-feeders do not produce this enzyme. Pollen-feeders that are unable to ingest grains may either pierce the grain and suck out the contents (thrips and biting-flies) or cause the grain contents to leach out an imbibe the leachate (butterflies and the eucalupt nectar fly). Pollen-feeders that can ingest the grains (bees, syrphid flies, rodents, marsupials, bats and birds) may use osmotic shock, pseudo-germination, exudation, microbial digestion or enzyme penetration to gain access to the protoplasmic contents. Further study is needed to define the details of these methods and whether they are all in use.

Includes bibliographical references (leaves 45-56). / Unimodal patterns of diversity along gradients of both disturbance and productivity rank amongst the most celebrated generalizations in ecology, known as the Intermediate Disturbance Hypothesis (IOH) and Productivity Diversity Hypothesis. However, doubt about their generality has arisen from studies that have failed to confirm the predicted patterns. Models suggest the interactive effects of disturbance and productivity on diversity to be responsible for the variability of diversity patterns.

Includes bibliographical references. / The bank cormorant Phalacrocorax neglectus is a seabird endemic to the south-western coast of southern Africa and the Benguela Upwelling System and has suffered a decline of more than 50% over three generations. Main threats include displacement by Cape fur seals Arctocephalus pusillus, direct human disturbance, pollution, climate change and food shortage. This thesis focuses on the bank cormorant’s response to food shortage, both directly and indirectly. Four colonies (Jutten Island, Dassen Island, Robben Island and Stony Point) were studied in terms of responses on population level in relation to the spatial distribution of prey surrounding the various colonies, foraging behaviour and breeding success. First, I tested the response of the bank cormorant ’ s population dynamics in relation to the availability of West Coast rock lobster Jasus lalandii in different spatial scales around three colonies (Jutten Island, Dassen Island and Stony Point) over a subset of years. I found that birds at Dassen Island showed the strongest response to the availability of rock lobster. Birds also showed strongest response to the availability of rock lobster in an accumulative distance around colonies, and their largest response was to rock lobster within 30 km distance from the colony. Various aspects including the life - history traits and moulting stages of this particular rock lobster species may be the reason to this response. Second, I present foraging effort data of bank cormorants in localities known to be situated in areas with different prey availability. I found that at Jutten Island, situated in an area where West Coast rock lobster have dramatically decreased, bank cormorants spent significantly longer time at sea than at Robben Island and Stony Point, which were situated in areas where rock lobster were known to be abundant at the time of the study. Third, I tested the effect of food availability on the breeding success of bank cormorants at Jutten Island, Robben Island and Stony Point. There was no significant relationship between food availability and the survival probability of the birds. The number of chicks fledged per successful nest, however was significantly related to the availability of rock lobster during the relevant breeding season, as well as during the relevant month of hatching.

Includes bibliographical references (leaves 63-68). / Catch and effort statistics for the Cape hakes (Merluccius capensis and M. paradoxus) have indicated a substantial decrease in the stock size over the period 1955-74; consequently, a catch projection model was designed to investigate the hake population. Where appropriate, available data have been included in the model; however, some further research was required: 1. The monthly pattern of availability for 1974-76 was examined using South African data; it was found to be similar to that reported for earlier years, and the later figures were used. 2. Assuming that selection curves for different mesh sizes are identical except for their position on the X-axis, a method to calculate selection values for combinations of mesh size and fish length has been outlined, and used with data presented by Bohl et al. (1971). 3. An investigation was made of two methods of estimating natural mortality (M), utilizing the results of Virtual Population Analysis (V.P.A.). In both cases the criteria used to judge M were found to be insensitive, and therefore neither can be used. 4. The stock estimates obtained using V.P.A. were applied to two stock/recruit curves. The goodness of fit in both cases was poor, and nearly identical.