Includes bibliographical references. / In this study cuticular scale patterns, groove size and hair measurements have been used as definitive criteria in identification of 42 species of the family Muridae. Keys for the use in identification have been made and detailed descriptions of the hairs of each species, together with micrographs of gelatin imprints and scanning electron micrographs are presented. The taxonomic and practical uses of this method are discussed. It has been found that the cuticular scale pattern on hairs of South African Murid species studied shows a remarkable specific constancy.

Bibliography: leaves 72-80. / An investigation was undertaken to determine whether triploidy could be induced and improve the growth rate of the South African abalone, Haliotis midae. From the polar body counts at 17 °C the release times of polar body 1 and 2 were found to be at 12 - 15 min. post insemination (pi.) and 33-36 min. pi. respectively. Cytochalasin B (CB) (0.5mg. 1-¹ seawater) and elevated temperature (30 °C) were used as stresses to induce triploidy. CB induced 48.4% polar body 1 and 70.9 % polar body 2 triploid larvae at 20 hrs pi. At 120 hrs pi. induction rates were 55.5% and 62.4% respectively. Temperature induction was more successful, producing 92.9% polar body 1 and 86.4% polar body 2 triploid larvae at 20 hrs pi. This success was still evident at 120 hrs pi, where 71.1 % polar body 1 and 62.5% polar body 2 triploid larvae were produced. In the CB induction, where polar body 1 was retained, there was a pronounced production of tetraploid larvae (34. 2%). It appeared that CB affected the ova's resistance to polyspermy, which was found to be dependent on both CB concentration and the amount of excess sperm present. At 0.4 mg 1-¹ CB in seawater, 86.5% triploids and 0% tetraploids were produced. However, on the addition of sperm, 25.4% triploids and 69% tetraploids resulted. CB (0.5 mg 1-¹ ) in seawater produced 42.6%> tetraploids which, after the addition of sperm, increased even further to 50. l % pentaploids. Larval survival was found to be low overall with only 17% and 22% of control (diploid) animals surviving the rearing period, in the temperature and CB treatments respectively. The survival rates of the polar body 2 treatment were 11 % and 15% whilst those of the polar body 1 treatment were 7% and 11 %. Although these percentages indicated a difference in survival rates between the CB and temperature inductions, the actual numbers of larvae surviving were the same. The polar body 1 triploid larval survival was significantly less than both control and polar body 2 triploid animals.

Bibliography: pages 139-150. / The South African Scoring System (SASS) is a rapid bioassessment technique based on one component of riverine biotas, the benthic macroinvertebrates. Each taxon is assigned a tolerance/sensitivity score, which are summed to provide a Total Score. The Average Score per Taxon (ASPT) is calculated by dividing this Total Score by the number of taxa. This study was undertaken to evaluate the SASS technique as a tool for the assessment of water quality. Three study-sites, which differed in water quality, in the south-western Cape were selected for a detailed investigation into sample variability and replication of two methods of biological assessment, namely quantitative box-sampling and SASS. The ability of each method to differentiate between these sites was determined. The more general application of SASS in the south-western Cape was examined at forty nine sites and potential problems associated with SASS, namely biotope availability, temporal variability and longitudinal changes were investigated. A minimum of twelve and four quantitative samples is needed to ensure collection of 95% or 75% of benthic macroinvertebrate taxa respectively. Sampling within a single biotope component, such as a "riffle" or "run" would reduce the number of samples needed. A minimum of four and two SASS samples is needed to ensure collection of 95% or 75% of the taxa respectively. This technique is however designed such that only one sample is taken per site. The Total Score that one sample would produce as a percentage of the Total Score from 20 samples, were 28% , 59% and 45% for Sites 1, 2 and 3 respectively. Total Score increases with increasing sampling effort, whilst ASPT is relatively unaffected by sampling effort. ASPT should therefore be used in interpretation of scores. Variability, as determined by both quantitative sampling and rapid bioassessment, was greatest at the least impacted site. Such sites should be more intensively sampled, either by increasing the number of box- samples taken, or by increasing the time period for SASS sampling.

Includes bibliographical references (leaves 36-41). / The future of abalone farming in Soulh Africa may provide benefits by the integration of abalone-seaweed re-circulation systems. This is a new system design of abalone fed on a kelp diet integrating seaweed culture facilitated by a re-circulation system. This kind of culture has the potential to increase abalone growth through increased water temperature, minimizing pumping costs while also incorporating production of on-farm seaweed resources. This has, however, the potential disadvantage to increase the suspended particulale concentration in the tank environment, with subsequent negative effects on abalone health. This study ties in with an existing Swedish-South African joint project. The results of this study will be used as inputs when trying to model a complete commercial recirculated abalone farm. Divided into two experiments this study records suspended particulate matter, particle size range and water nutrient concentrations (phosphate, ammonium and nitrite).

Bibliography: leaves 34-39. / The driving forces behind changes in copepod community structure in the Benguela upwelling region are examined. For this study, monthly changes in copepod size structure and species composition were examined at St Helena Bay in 2000/1 in relation to upwelling, phytoplankton and fish. The copepod assemblage was dominated by large species categories in the early period of recruitment (April) and smaller species categories in the late period of recruitment (August). The reappearance of large species categories and increase in copepod biomass is observed in summer months. This is attributed to both predation and upwelling intensity. Arguments are developed to suggest that the copepod size. structure is consistent with 'wasp-waist' control and 'bottom-up' control was responsible for the copepod increase.

Bibliography : leaves 98-109. / This is the first biological study of four endemic catshark species, Haploblepharus edwardsii, H. pictus, Poroderma africanum and P. pantherinum, from the southwestern Cape. Diets of two hundred and forty-one specimens were examined via stomach contents. Prey were sorted and identified to the lowest possible taxon. An Index of Relative Importance (IRI = %F(%N + % V) was used to determine the importance of prey items in the catsharks' diets.

Includes abstract. / Includes bibliographical references. / Phytoplankton community composition in the Southern Ocean (SO) determines levels of primary production, which support marine ecosystems and export of material to the deep sea. Nanoplankton (cell diameters 2-20 μm) are poorly resolved by traditional microscopy, and it is becoming apparent that unknown diversity and ecosystem functionality may be contained in this size class: for example, small diatoms (< 10 μm) appear widespread in the SO, and may limit our understanding of the response of phytoplankton communities to climate change.

Bibliography: pages 57-66. / The feasibility of obtaining information on the dispersion of seabirds at sea precise enough to reflect changes in their prey was investigated. A standardized technique for counting birds from a moving ship, designed to limit biases due to birds circling, following and/or deviating towards/from the ship, is suggested. An interspecific comparison of 31 seabird species was made to determine which species yielded the most accurate censuses. Although many species are attracted towards the ship, only the Wandering Albatross Diomedea exulans follows for long periods. Counts from a stationary ship are shown to be unsuitable for abundance and biomass estimates, because of the accumulation of birds around the ship. The avifauna at sea is described in terms of species richness, diversity, abundance, biomass and trophic groups of 42 pelagic species (penguins excluded). Birds eating plankton and cephalopods are the most abundant; few birds eat fish. Plankton- and cephalopod-eaters occur most abundantly in the south and north of the study area, respectively. An association between their distribution and the availability of their principal prey is proposed. The effect of five abiotic features on seabird distribution was investigated. Although significant preference for specific ranges of features is demonstrated, linear correlations are weak (maximum correlation coefficient (r = 0.325). Abiotic features associated with the distribution of the Snow Petrel Pagodroma nivea and the Antarctic Petrel Thalassoica antarctica were investigated in greater detail. Statistical relationships between the species' occurrence and measured oceanographic and meteorological features are inconclusive. Associations with prey are discounted, because of the birds' apparently unspecialized diet and opportunistic feeding. The two species occur in or near sea-ice. Their restriction to this area and the concomitant absence of other procellariiform species appears to be consequent on the species' flight characteristics. The merits of using seabirds at sea as biological indicators of prey resources are discussed.

Includes abstract. / Includes bibliographical references (leaves 87-99). / The main objective of this study was to describe the use of intermittently open estuaries (IOEs) along a section of the Eastern Cape coast by waterbirds, and the factors that influence avifaunal community composition in space and time. The study area consisted of four IOEs of varying sizes within a 40 km stretch of coastline in the warm temperate coastal biogeographical region of South Africa.

Includes bibliographical references (leaves 78-94). / Acacia cyclops A. Cunn ex G. Don, or rooikrans (Fabaceae), of Australian origin, is an invasive environmental weed in South Africa where it threatens the unique vegetation of the Cape Floral Kingdom. The invasiveness of the plant in South Africa is, in part, due to its high annual seed-yields, together with the suitable climatic and edaphic factors found here. This study investigated the role of a seed-feeding weevil, Melanterius servulus, which was first introduced into South Africa during 1991, as a biological control agent of A. cyclops seeds, together with the combined effects of indigenous seed-sucking bugs and birds. The weevils utilise filled green pods of A. cyclops for adult feeding, oviposition and larval development and completely destroy seeds during these activities. Examination of the reproductive phenology of A. cyclops showed that seeds are produced annually, during summer and that the presence of filled green pods on the plants coincides with the period of reproductive activity of the weevils. Melanterius servulus populations have established readily at all the original release sites, and within four years of release, damage levels to seeds commonly reached 90%. The weevils have dispersed at an average rate of approximately 2 km per year. Since becoming established in South Africa. the seeds of A. cyclops have been utilised by a variety of generalist vertebrate and invertebrate organisms. Indigenous polyphagous alydid bugs feed on the mature seeds, rendering a portion of the crop inviable when damage levels are high (more than five feeding-punctures per seed). Several bird species are attracted to and feed on the fleshy aril that surrounds theseeds of A. cyclops. Passage of the seeds through the gut of birds enhances germination rates. There is a synergetic relationship between alydids and birds because seeds with low levels of alydid feeding (one to four punctures per seed) germinated more readily after passage through birds than seeds that were not eaten by birds.