Many coastal fish exhibit age-specific differential distribution and shallow inshore regiong provide nursery habitats for juveniles of some species. In this study the occurrence of juvenile fish along the Eastern Cape coast was examined with the objective of assessing the importance of coastal habitats as nursery areas for the common coastal teleosts. The thesis comprises ten separate research papers and an overview of coastal zone utilization by juvenile teleosts in the Eastern Cape. Research was concentrated in Algoa Bay and covered the nearshore ichthyo-plankton, tidal exchange of fish eggs, larvae and juveniles across the mouth of the Swartkops estuary, the ichthyofauna of the Swartkops and Sundays estuaries, the juvenile fish associated with subtidal soft substrata and rocky reefs and the ichthyofauna, occurring in tidal pools on rocky shores.

Bibliography: pages 320-327. / A 120 station grid was surveyed at monthly intervals in the southern Benguela. Current system between August 1977 and August 1978. Plankton was collected at each station by means of a double oblique tow behind the ship at 2 knots down to 100m or 5m off the bottom. Plankton displaced volume was determined and all fish eggs and larvae were removed and identified to the lowest possible taxon. Water samples were collected at each·station by means of 5 litre bottles from 5 depths down to a maximum depth of 75m. Microplankton (37-100 μm fraction) particle concentration, chlorophyll concentration and salinity were determined from the samples. A vertical temperature profile was obtained at each station using a bathythermograph. Twenty plastic drift cards were released at each station and recoveries plotted. Wind measurements were made on board the ship and also obtained after the cruise from land sites at Cape Point and Cape Columbine. After August 1978, the CELP grid was resurveyed in November 1978, November 1981 and November 1982. In November 1979 and November 1980 a number of stations were sampled in the vicinity of the Cape Peninsula. to determine the vertical abundance pattern of anchovy eggs. In November 1983, 1984 and 1985 a much larger portion of the southern Benguela Current system was surveyed to determine the spawner biomass of anchovy using the egg production and acoustic methods. In these surveys anchovy eggs were sampled by means of a vertical tow with a CalVET net and at some stations on the Agulhas Bank the vertical abundance of anchovy eggs was sampled using a multiple opening and closing RMT sampler. The ichthyoplankton and environmental data were interpreted to reveal any similarity in pattern. Anchovy, hake and laternfish were selected for special attention because of their different spawning strategies, and were shown to have seasonal and spatial patterns of egg and larval abundance which could be related to the environment. The major environmental process influencing ichthyoplankton abundance patterns appeared to be the seasonal advection of warm western boundary current water into the system from late spring to early autumn, causing the development of a temperature front along the west coast and a thermocline over the Agulhas Bank. Plankton standing stocks were elevated between the front and the coast and in the thermocline. In order to place their spawning strategies into perspective, a simulation model was used to explore the performance of anchovy, hake and lanternfish life history strategies in filtering out environmental variability. Results suggested that anchovy and hake are adapted to cope with variability whereas lanternfish are less well adpated, and therefore spawn in winter when the system is most homogeneous. Conclusions are drawn as to the kinds of environmental anomalies likely to cause poor year class strength in the three species.

No description available.

Includes bibliographical references (leaves 184-210). / Horseshoe bats (genus Rhinolophus) belong to the Old World family Rhinolophidae. They are high-duty cycle bats and many species use echolocation calls dominated by high frequencies (above 60 kHz). Much is known about how they use their echolocation calls, but very little is known about why these bats use echolocation calls of such high frequencies, or what has caused the divergence in echolocation call frequency between rhinolophid species. I test five hypotheses that may explain the evolution and divergence of high frequencies in the horseshoe bats: (1) The Allotonic Frequency Hypothesis - echolocation frequencies outside of moth hearing range (allotonic frequencies) have evolved in response to moth hearing; (2) The Allometry Hypothesis - highfrequency echolocation calls are simply a function of body size; (3) The Acoustic Adaptation Hypothesis - selection pressures linked to habitat structure have shaped the evolution of high-frequency echolocation calls; (4) The Foraging Habitat Hypothesis - foraging style and habitat of a bat should correspond to echolocation call frequency and wing design; and (5) The Acoustic Communication Hypothesis - echolocation frequencies evolved under selection pressure which eliminated overlap among sympatric species of rhinolophids, within the context of effective communication.

Intensifying hydrologic alteration and the resultant degradation of river ecosystems worldwide have catalyzed a growing body of ecohydrological research into the relationships between flow regime attributes, physical habitat dynamics and biotic response, particularly for determining environmental flows. While invertebrate response to floods has received most attention, in this thesis the aim was to identify and characterize low flows that constituted various degrees of physical disturbance to benthic macroinvertebrate assemblages of perennial rivers.

Includes abstract. / Includes bibliographical references (p. 113-127). / The study assessed the welfare value of fisheries in reducing income poverty and economic vulnerability in the Kafue and the Lower Shire floodplains under the hypothesis that inland small-scale floodplain fisheries significantly reduce poverty and vulnerability in fishing households. The welfare value was also analysed in the context of management regimes of the two floodplain fisheries. The relationship between inter-annual fish production, agricultural production and local rainfall was also evaluated.

Bibliography: leaves 342-359. / How and why did limblessness evolve in certain skinks? These questions are explored in certain species of the Scincidae (from southern Africa) that vary in the degree of limb reduction. This regression series consists of Mabuya capensis (with normal, pentadactyle limbs), Riopa sundevallii (with miniaturized, pentadactyle limbs), three species of the genus Scelotes (bipes, gronovii and brevipes - with vestigial hindlimbs varying in the degree of degeneration) and, finally, Acontias meleagris(without any trace of limbs). The osteology and the myology of the locomotor apparatus are described for all members of this regression series with special reference to the axial system which has in the past received but scant attention compared with the appendicular apparatus. Qualitative and morphometric data are used to construct morphoclines that are correlated with limb reduction. Numerous morphological trends and tendencies support the conclusion that the axial system hypertrophies as the appendages degenerate. The patterns of locomotion are also described for all members of the regression series. Furthermore, an ethocline, that links the limbed and limbless extremes, is postulated. Even in quadrupedal skinks the dominant appendicular system may be assisted by axial flexures that increase stride length. As limbs degenerate, appendicular progression is phased out while axial progression increases in importance.

Includes bibliographical references (leaves 111-148). / In Chapter 1, I characterize geographic patterns in rocky intertidal communities across 6° of latitude along the west coast of South Africa and examine the spatial structure of functional group biomass in relation to wave action and upwelling intensity. Despite between-habitat differences in biomass, most functional groups showed similar regional trends in exposed and sheltered habitats, but weaker non-significant between-habitat associations were observed when considering differences due to site. Divese geographic trends were observed, with only specialized kelp-trapping limpets showing a smoothly decreasing trend with latitide. Abrupt changes in the abundance of several species were observed at about 32° or near 34.5° S. Correlations between functional groups were strongest in the low (exposed) and mid (sheltered) shores, and supported the possibility that species interactions, particularly (1) competitive dominance by filter feeders and gardening limpets and (2) habitat facilitation by filter feeders partially account for local differences in functional-group abundances. Nearshore oceanographic conditions were characterized using satellite-measured sea surface temperature (SST), verification by in situ loggers, and analysis of Offshore Ekman Transport (OET) indices. A clear discontinuity at about 32° S partitioned the coast into a northern region characterized by consistenly strong and spatially homogenous upwelling, and a southern region distinguished by significant mesoscale variation in seasonal upwelling intensity among sites, with clear upwelling centers alternating with "downstream" areas only weakly influenced by upwelling. Functional group relationships with SST differed between north and south regions. Local abundances were generally more variable in the south, where greater biomass of ephemeral and corticated macroalgae, as well specialized gardening and kelp-trapping limpets, were associated with upwelling centers. In contrast, high-shore filter-feeder and predator biomasses were significantly greater at downstream sites. These results suggest that oceanographic discontinuities around 32° S may frame community dynamics and that upwelling intensity influences community structure and generates regular spatial differences in interaction webs along the South West Cape. This study represents the critical first step to identifying spatial scales at which processes regulate communities, and provides a series of testable hypotheses that can be evaluated by experimental comparative approaches.

Includes bibliographical references. / When compared to northern temperate counterparts, birds in the tropics and Southern Hemisphere regions, are characterised by low fecundity, long developmental periods and high Survival. This pattern has been attributed to hypotheses relating to food limitation, nest predation, and reduced seasonality leading to high adult survival. Still, to date few studies have investigated this issue. In particular, detailed studies from southern regions are scarce and as a result our understanding of this question remains weak. Another characteristic of 'southern' birds is a higher frequency of cooperatively-breeding species. It has previously been shown that cooperative breeding is most frequent amongst species with high survival and low fecundity. An explanation for this could be that long occupancy of territories by long-lived breeders leads to reduced opportunities of independent breeding by young birds. However, the biology of some species is such, that they do not experience shortage of breeding territories or other constraints, while still showing delayed dispersal and cooperative breeding. This study investigates what factors drive life-history evolution in a cooperatively breeding southern African passerine, the sociable weaver Philetairus socius. This species departs from the traditional cooperative breeding model in being a non-territorial colonial nester that inhabits an unpredictable semi-arid environment. Sociable weavers face no obvious constraints on independent reproduction, yet cooperative breeding is common. Therefore, I also aimed at determining what factors prompt delayed reproduction in this species, since this life history trait is the first step leading to cooperative breeding.

Bibliography: p. 492-494. / This thesis provides a complete taxonomic review of South African hermatypic Scleractinian reef corals, a description of coral communities on northern Natal coral reefs, experiments isolating the influence of the most important abiotic factors forcing these communities and finally management suggestions for the marine reserves within which these reefs are situated, based on the results of the ecological investigation. The taxonomic part reviews the entire hermatypic scleractinian coral fauna of South Africa and Southern Mozambique, including also material from the Atoll Bassas da India in the Mozambique channel. The study of coral communities on Northern Natal coral reefs revealed major differences in the nature of the reefs and the community structure of the reef corals from typical coral reefs in the Inda-Pacific. The study lead to the assumption that wave-action and sedimentation are the most important abiotic factors influencing these coral communities. These hypotheses were experimentally tested in the field and in the laboratory, using indicator species for specific community types, as identified in the community study. Testing fragment survival of the hard coral Acropora austera confirmed the assumption that wave action is an important factor shaping coral communities by only allowing this species to dominate in depths greater than 18m. Four hard- and five soft coral species were used to quantify the effects of sedimentation on the coral communities. It was demonstrated that long-term sedimentation had greater influence on soft corals than on hard corals, leading to tissue necroses and local bleaching. These experiments confirmed the assumption that sedimentation is a major forcing factor on South African coral communities. The final part of thesis provides management options for the St. Lucia and Maputaland Marine Reserves focussing on conservation of the coral communities. The findings obtained in the ecological investigation allowed to identify which activities in the reserves have to be controlled in order to minimize damage to the coral communities by park visitors.