Bibliography: pages 70-74. / Feeding of the redeye roundherring Etrumeus whiteheadi Wongratana 1983, was investigated off the west and south coasts of the Cape Province of South Africa. Fish from the west coast were collected in April and May 1984, those from the south coast during November 1983 and 1984. Diet was determined from stomach contents. Dry mass and numbers of food items are presented. Copepods were the principal food off the south coast, constituting a mean of 67% (range: 60-75%) by mass of gut contents in juveniles, a mean of 59% (range 44-88%) in the transitional juvenile/adult size class and a mean of 43% (range: 30-73%) by mass in the adults. Adult and larval stages of euphausiids were also an important dietary component of these fish, comprising a mean of 10% (range: 0-18%) by mass in the juveniles, a mean of 14% (range: 7-18%) in the transitional juvenile/adult size class and a mean of 52% (range: 27-63%) by mass in the adults. On the west coast chaetognaths appeared to be the principal food item of the juvenile fish examined, yielding values as high as 99% by mass. Other less important prey in both areas included cladocerans, ostracods, fish eggs, pteropods, bivalve larvae, squid and juvenile fish. Phytoplankton formed a negligible component of the diet. It was present in minute quantities in the west coast fish only. Diurnal feeding patterns were investigated for both areas. Total mass of stomach contents constituted a maximum of 1.2% of total fish mass off the south coast in November 1983, and a maximum of 0.85% in November 1984. Off the west coast, where juveniles only were sampled, the stomach content mass made up to 7% of body mass. Stomachs were fullest in the afternoon and early evening and it is inferred that feeding takes place during daylight hours. Predator-prey size relationships were investigated using two methods. The first method involved testing the correlation between fish mass and prey mass and the second employed Ursin's procedure using predator-prey mass ratios. Predator size was found to have a small effect on diet composition.

Bibliograpy: leaves 87-101. / A Geographic Information System (GIS) is used to elucidiate vertical and horizontal patterns of distribution of Merluccius capensis on the inshore south coast (20°-27°E) of South Africa. Catch data used to compare the size distribution in catches made by commercial trawls and longlines off the South Coast (20°E). Results show that M.capensis size increases with depth and that the distribution of fish < 30 cm is mostly west of 23° E with isolated pockets east of that region. No seasonal differences were found in the distribution of this species. Spatial mapping of survey trawl and longline grounds of the Agulhas bank whereas longlines operate over rocky areas. Size comparisons of the catches of the two fishing methods reveal that longlines catch very few fish that are < 60 cm whereas trawl cataches are dominated by M. capensis of length < 60 cm. Analyses also revealed sex compostion in longline cataches to be different to that of trawls. All these results are discussed in relation to the ecology of M. capensis and the areas where data come from. Using size selectivity properties, the potential impacts of longlining and commercial trawling on the South Coast M. capensis (east of 20° E) are modelled with a yield per recruit and spawner biomass per recruit model. First, the age-specific selectivity vectors of the two fleets are estimated from catch data (length frequencies).

The coast of South Africa is one of the most biologically diverse marine systems in the world but little is known about the parasites occurring in this environment. A survey of the parasites of an intertidal clinid, Muraenoclinus dorsalis Bleeker, 1860, captured from Granger Bay, Kommetjie and Jacobsbaai, South Africa during Summer 2008/2009 and Winter 2009 revealed twenty-three parasitic species. Five myxozoans, all likely new to science, were found to infect M dorsalis. Ceratomyxa sp. and Sphaeromyxa sp. 1 were found in the gall bladder and bile ducts, Kudoa sp. in skeletal muscle, and a Myxobolus sp. on the eyes. Spores of Ortholinea sp. were also detected in gall bladder squashes, but the actual location of infection is unknown. The endoparasite community composition and structure, and their persistence over space and time were also probed. Non-metric multidimensional scaling, cluster analysis and Analysis of Similarity showed that community composition during both summer and winter differed most between Kommetjie and Jacobsbaai, the sites geographically furthest apart. This observation implies a decay in similarity over geographic distance. The endoparasite component communities from Granger Bay showed no significant dissimilarity in composition between summer and winter while the component communities from Kommetjie showed little dissimilarity (Global R: 0.105; p-value = 0.002). These results suggest that season or seasonassociated factors play weak roles at both localities. Contrastingly, the summer and winter component communities from Jacobsbaai showed significant dissimilarity (Global R: 0.201; pvalue = 0.003) because of the higher parasite load in winter. This is attributed to the sheltered nature of Jacobsbaai, where violent winter waves do not disturb the fish but rather push up the tide thereby extending the submergence period of M dorsalis. A longer period of submergence may provide parasites with increased opportunities to infect a host. Nestedness analysesconfirmed a nested subset structure in all component communities, likely a result of differentiated colonization, passive sampling, or a combination of both. This result lends evidence to the theory that parasite community structure is persistent over space and time and that there are laws in parasite ecology.

Bibliography: leaves 137-149. / This thesis presents results of studies conducted on banks of kelp stranded on a sandy beach at Kommetjie on the west coast of the Cape Peninsula. The physical and chemical character of the beach are related to variations in the standing stocks and productivity of macro-, meio-fauna and bacteria as determined from a quantitative survey conducted on a monthly basis throughout 1981. Tracer experiments were carried out to establish the partitioning of dissolved organic matter between the different faunal elements (namely bacteria and meiofaunal present in the sand below decomposing kelp. Finally, a description of the flow of energy through the wrack bed ecosystem is given.

Bibliography: leaves 191-196. / This thesis stemmed initially from the author's desire to investigate the phytoplankton assemblages of the freshwater vleis of the Cape Peninsula. This aspect of the limnology of the Cape Flats vleis has received only scant attention by other researchers (over 40 years ago), and no comprehensive studies of their seasonal phytoplankton periodicities had been attempted. The paucity of information regarding the phytoplankton of the winter-rainfall, Mediterranean-climatic systems of the Cape Peninsula was found to not only be limited to South Africa. The literature survey undertaken for this study (Chapter 1) revealed•a general lack of information for shallow, nutrient-enriched, coastal systems, with virtually no data available for coastal systems in winter-rainfall regions. The thesis includes a description not only of the phytoplankton, but also of the limnology of each vlei as they are currently understood; this information is synthesized in Chapters 2 and 3 and collates all the available information accumulated by the Cape Town City Council (CCC) since it commenced monitoring of both vleis almost a decade ago. These chapters also contain details of the available bibliography for each system and form the first compilation of the available data for these waters. The inclusion of these chapters enabled comparisons to be made between the water chemistry regimes during the current study with those prevailing during earlier years. During the course of the study the author came across other pertinent aspects of each vlei which necessitated sub-investigations. The details of these are also included in the limnological chapters.

Bibliography: leaves 167-206. / This study focused on elucidating the functional significance of some aspects of the behaviour of Koch's barking gecko, Ptenopus kochi, during a field season conducted at the Desert Ecology Research Unit in Namibia for four months in 1995. Ptenopus kochi is a terrestrial species, and males were observed calling from their burrow entrances in the dry Kuiseb river bed during the hot summer months. First, aspects of competition among calling males were investigated. Calling males were seen to be non-randomly distributed relative to one another with evidence for regularity of spacing in dense aggregations. Sound intensity was investigated as the mechanism of spacing, and was mathematically modelled to gauge how the intensities of the calls of nearest-neighbour males overlapped. Results revealed a constancy at which neighbouring call intensities overlap, and playback experiments ratified the presence of a critical intensity threshold in the population, beyond which male tolerance broke down. These results suggested that spacing in P. kochi is vocally-mediated and that sound intensity acts as the proximate cue through which individuals gauge the closeness of neighbouring males. Second, the inter-relationships between call features of P. kochi's vocalisation, and how these features related to both intrinsic (morphological) and extrinsic (ambient) sources of variability were analytically explored. The principles of information theory and individual recognition by voice were used to gauge the variation manifest in the features of P. kochi's call. A novel statistical method for disentangling the influence of incidental sources of variation from 'signal' features in animal voices was developed. Results showed how once the predictable covariance in call structure was removed, the calls of P. kochi males were rendered statistically indistinguishable from one another. Several descriptor measures of P. kochi's vocalisation were seen to be highly dependent on meteorological determinants, as was nightly chorus duration. Lastly, mate-choice in P. kochi was explored using correlational evidence. Results revealed that mating success was closely linked to individual male differences in display effort and chorus site burrow activity, and less to morphological or territorial characteristics. Counter-intuitively, a positive relationship between call rate and chorus site residency was found in males, suggesting a possible role for classical condition-dependence in the evolution of female mate preference. Aspects of mate choice, together with the emergent importance of residency in this study were discussed and some ideas suggested for further research.

According to Brown's hypothesis, generalists have high niche breadth and can tolerate a wide variety of environmental conditions resulting in large geographic range sizes. Conversely, specialists have low niche breadth and small range sizes. I tested this hypothesis using African Horseshoe bats to determine if differences in niche breadth can explain variation in geographic range size.

Includes abstract. / Includes bibliographical references (p. 40-46). / Branchial sieves of southern African sardine (Sardinops sagax ocellatus) were collected from three geographical regions along the southern African coast: Namibia, the south coast and the west coast of South Africa. Sardine from Namibia represented the northern Benguela upwelling ecosystem while sardine from the west and south coasts of South Africa represented the southern Benguela upwelling ecosystem. Morphometric measurements (gill arch length and gill raker spacing) and counts (number of gill rakers) of branchial sieves on the left side of the first gill arch were taken to determine whether the sardine from these regions have different branchial sieve structures.

Members of the AKHIRPCH family of peptides were identified in corpora cardiaca of the dragonfly Anax imperator (Anisoptera: Aeshnidae), Orthetrumjuliajalsum (Anisoptera: Libellulidae) and the damselflies Pseudagrion inconspicuum and Ischnura senegalensis (Zygoptera: Coenagrionidae). After isolation ofthe peptides by reversed phase high performance liquid chromatography, the primary structures were established by Edman sequencing and mass spectrometry (Ani-AKH: pGlu-Val-Asn-Phe-Ser-Pro-Ser-TrpNH 2 ), (Lia-AKH: pGlu-Val-Asn-Phe¬ Thr-Pro-Ser- TrpNH 2 ) and (Psi-AKH: pGlu- Val-Asn-Phe- Thr-Pro-Gly- TrpNH 2 ). One corpus cardiac of A. imperator contains about 40 pmol Ani-AKH, O. julia 19-24 pmol Lia¬ AKH and P. inconspicuum about 2.4 pmol Psi-AKH. Injection of Ani-AKH (3.4 pmol) increased the concentration of haemolymph lipids in A. imperator. Lia-AKH (l pmol) similarly had an adipokinetic effect in 0. julia. Psi-AKH (I pmol) had an adipokinetic effect, as well as a small hyperglycaemic effect in P. inconspicuum. The AKH peptides of other Odonata were investigated. In the suborder Anisoptera, Ani-AKH was identified in representatives of the Aeshnidae, Cordulegasteridae, and possibly the Corduliidae. Lia¬ AKH was identified in representatives of the Libellulidae and Gomphidae. In the suborder Zygoptera, Psi-AKH was identified in representatives of the families Chlorolestidae, Lestidae and Chlorocyphidae, and possibly the Calopterygidae and Protoneuridae. Classification of Odonata according to their flight behaviour as "perchers" or "fliers" is supported by parameters of energy metabolism. Lipid metabolism seems to have a greater importance in fliers than perchers. The lipid concentration in the haemolymph is highest in the flier A. imperator, intermediate in the percher 0. julia and lowest in the percher P. inconspicuum. There are indications that mitochondria isolated from flight muscles of A. imperator may have a higher capacity for lipid oxidation than 0. julia. The contribution of carbohydrates to flight metabolism seems to be more important in perchers than in fliers. The concentration of carbohydrates in the haemolymph is highest in P. inconspicuum, intermediate in O. julia and lowest inA. imperator. The maximal activity of phosphofructokinase (a rate-limiting enzyme of glycolysis) is higher in the percher, O. julia, than in the flier, A. imperator. The lipid concentration in the haemolymph is higher than that of the carbohydrates in O. julia, A. imperator and P. inconspicuum. Palmitoyl-carnitine is oxidised at high rates by isolated mitochondria from flight muscles of O. julia andA. imperator, similar to Locusta migratoria. Lipid is the major fuel utilised during flight in O. julia. Carbohydrates (in the haemolymph) and proline (in the haemolymph and flight muscles) are utilised as minor fuels. It is concluded that the processes of lipid metabolism provide the major source of energy during flight in Odonata. The AKH peptides seem to play a role in regulating lipid mobilisation during flight in Odonata.

Bibliography: pages 41-47 / The surplus production model and ad hoc tuned VPA assessment methods currently used to provide the basis for scientific TAC recommendations for the Cape hake resource off South Africa provide rather different appraisals of the current status and productivity of this resource. The production model approach is based on the Butterworth-Andrew observation error estimator, and takes catch per unit effort (CPUE), as well as biomass survey data into account. The ad hoc tuned VPA is based on the Laurec-Shepherd tuning algorithm and utilizes catch-at-age and effort information. Applications of an age-structured model, which takes both CPUE and catch-at-age data into account, provides similar results to the production model if more weight is given to the CPUE data than the catch-at-age data and similar results to the ad hoc tuned VPA if more weight is given to the catch-at-age data rather than the CPUE data. This led Punt (1993) to conclude that the discrepancies between the various sets of results obtained from surplus production model and ad hoc tuned VPA methods are a consequence of a conflict between the catch-at-age data and the CPUE data and that they are not primarily a result of differences in the two assessment methods. However, the above two approaches are based on certain assumptions regarding recruitment, natural mortality and fishing selectivity. An attempt was made to obtain estimates of fishing selectivity-at-age from an age-structured production model. It is commonly assumed that selectivity-at-age has a slope of zero at older age classes. The estimates obtained all suggest that selectivity-at-age for older age classes (> 2 to 3 years) decreases with age. The results obtained in this study also indicate that the conflict between the observed trends in the catch-at-age data and the CPUE data can be basically resolved by assuming that for older age classes selectivity-at-age decreases.