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An ecological study of territoriality in four Cichlid species resident on rocky shores near Monkey Bay, Lake Malawi

  • Authors: Sharp, Bradley John
  • Date: 1982
  • Subjects: Cichlids -- Nyasa, Lake , Cichlids -- Behavior
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:5340 , http://hdl.handle.net/10962/d1005927 , Cichlids -- Nyasa, Lake , Cichlids -- Behavior
  • Description: This study centres on a diverse assemblage of epilithic algal grazing fish (17 cichlids and 2 cyprinids) found on the rocky shores near Monkey Bay, Lake Malawi. Diet overlap among these species is large, but competitive exclusion is apparently avoided by the species having different feeding structures, behaviour and distribution on the shore. In many respects the ecology and behaviour of the cichlid fishes inhabiting the rocky zones of Lake Malawi parallel those of coral reef fish. In both communities there are species which are highly territorial, resulting in resource subdivision and, in some cases, the development of algal gardens. As this behaviour has not been previously reported for cichlid species, this thesis describes the territoriality of the rock-dwelling cichlids of Monkey Bay, Lake Malawi, and poses three specific questions: 1. What is the function of territoriality? 2. How do the territorial species subdivide the space resource? 3. What prevents one species taking over all the available space? It is suggested that interspecific territoriality evolved in response to a shortage of food, and, at present, serves principally to defend an algal garden i.e. a food supply of high standing crop. The species studied are extremely site specific. The rocky shore is subdivided among the four species according to the rock configuration, size, algal mat composition and position on the shore, of the available sites. An experimental study of the space utilization of the two common territorial species, referred to as 'Pseudotropheus orange cheek' and 'Pseudotropheus aggressive', showed that suitable territory sites are in short supply and that these species are in competition for some sites. These results do not support those of Fryer (1959) who suggested that a superabundance of food enabled fish to coexist by sharing the same food resource. Indeed it now appears that a shortage of food may have been a major driving force during the recent evolution of the species studied.
  • Full Text:
  • Date Issued: 1982

An ecophysiological study of the effects of changes in salinity and temperature on the distribution of Macrobrachium Petersi (Hilgendorf) in the Keiskamma river and estuary

  • Authors: Read, Graeme Hamilton Leonard
  • Date: 1982
  • Subjects: Macrobrachium -- South Africa
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:5804 , http://hdl.handle.net/10962/d1006304
  • Description: Summary: The distribution of adult, juvenile, post larval and larval Macrobrachium petersi (Hilgendorf) was studied in relation to temperature and salinity in the Keiskamma river and estuary from May 1979 to May 1981. M. petersi is a subtropical species, which confined activity of all stages in the field to the summer months. Variable freshwater discharge and tidal effects determined the salinity and temperature profiles in the middle and upper reaches of the Keiskamma estuary. Thus, a dry 1979/80 summer and a wet 1980/81 summer markedly influenced the abundance and distribution of adult M. petersi in the river and estuary respectively. Adult M. petersi migrate to the estuary under flooding conditions and upstream in response to elevated salinities. Although M. petersi has nine larval stages only a preponderance of stage I were caught in the field. These portray a distinct nocturnal and diurnal distribution pattern which is influenced by salinity, especially under stratified conditions. After flooding the larvae show an affinity for salt front regions and reach these by remaining in the water column on the ebbing tide. A substantial drop in abundance downstream from the salt front suggests that the larvae loose their planktonic phase which is an effective retention mechanism, and confines larval development to the middle and upper reaches of the estuary. Post larvae were caught towards the end of the 1981 breeding season which indicates that complete larval development takes place in the estuary. A post larval migration to freshwater, which reaches a peak in February and March, was monitored. Thus both the freshwater and estuarine environments form an inseparable link in the life cycle of M. petersi. The distribution of stage I larvae in the Keiskamma estuary suggested that salinity played a role in development. The fact that other larval stages were not found emphasised the necessity for a quantitative laboratory investigation to determine the importance of salinity in the developmental history of M. petersi larvae and post larvae. However, the modifying influence of temperature could not be ignored so a multivariable approach was adopted. This, together with a surface response technique, aided the interpretation of the effect of a variety of combinations of salinity and temperature on ecdysis to stage II, larval survival and requirements for metamorphosis to post larvae. It was estimated that the minimum salinity requirement for complete larval development, within a temperature range from 18 to 30⁰C was 8%₀, although ecdysis to stage II and metamorphosis to post larvae could occur in salinities less than this value. Despite the euryhalinity of the larvae, the behaviour of adult M. petersi to an increase in salinity and the affinity of stage I larvae to salt front regions restricted development to the upper reaches of the estuary. This is discussed as an adaptation which not only ensures retention within the estuary but favours recruitment to the adult population in freshwater. The osmoregulatory patterns of larval, post larval, juvenile and adult M. petersi correlated with their distribution. These were approximated by a cubic polynomial which enabled the different patterns to be compared. The larval stages investigated (I, II, V & IX) displayed a remarkable capacity to regulate which was strongest in stage I as these could regulate in both freshwater and 35%₀. The ability to regulate in freshwater was lost hereafter but regained in the post larvae, which also regulated in 35%₀. Juveniles (caught at the ebb and flow) displayed a similar regulatory pattern to the adults and "hyposmoconformed" in salinities beyond the isosmotic point as the need to regulate in 35%₀ was no longer necessary. The osmoregulatory capacity of M. petersi larvae in relation to other decapod larvae is discussed. Marine transport of the euryhaline larval and post larval stages accounts for the distribution of M. petersi along the South African coastline. However, south of 31°S latitude the sea-surface temperature decreases abruptly. This region coincides with the southern limit of the distribution of M. petersi. Although larval M. petersi can tolerate high salinity (35%₀) in combination with low temperature, the post larvae cannot, which is likely to account for their restricted southern distribution. The genus Macrobrachium are in the process of invading freshwater. The possible course that this might have taken has been discussed in the light of available evidence as well as the findings of this study.
  • Full Text:
  • Date Issued: 1982

An evaluation of the effects of imported insects on the weed Lantana camara L. in South Africa

  • Authors: Cilliers, Catharina Johanna
  • Date: 1982
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:5808 , http://hdl.handle.net/10962/d1006853
  • Description: The plant, Lantana camara L. (V erbenaceae), is a weed in tropical and subtropical areas around the world. In many countries, including South Africa, biological control of this weed has been attempted. Although 12 insect species have been imported into South Africa, only four species established and these are dealt with in this study. Ophiomyia lantanae Diptera: Agromyzidae, a seed fly, is briefly dealt with; the main emphasis is on the leaf damaging species Teleonemia scrupulosa Stål (Hemiptera: Tingidae) and two leaf mining beetles, Octotoma scabripennis Guerin and Uroplata girardi Pic . (Hispidae: Coleoptera). In evaluating the insect damage to lantana leaves, monthly samples of branches were taken over three seasons from 1977- 80. This destructive sampling allowed the study of population build-up of the insects. In addition, counts were made of the numbers of damaged and healthy leaves, flowers and seeds and the damage related to the activities of the different stages of the hispids and the tingid. Insect exclusion experiments were also used to determine the effect of the insects on the growth of L. camara. The results reported in this thesis clearly indicate that the imported natural enemies retard L. camara growth and vigour and the effects are manifested in a marked reduction in stem diameter, internodal length, leaf size, leaf lifespan and in flower and seed set.
  • Full Text:
  • Date Issued: 1982

An examination of the finances of the Cape Midlands Administration Board, 1973-79

  • Authors: Humphries, Richard G
  • Date: 1982
  • Subjects: Cape Midlands Administration Board Cities and towns -- South Africa Local government -- South Africa -- Eastern Cape Finance, Public -- South Africa -- Eastern Cape
  • Language: English
  • Type: Book , Text
  • Identifier: http://hdl.handle.net/10962/2161 , vital:20261 , ISBN 0868100935
  • Description: While the Bantu Affairs Administration Board Act was passed by Parliament in 1971, it was not until July 1973 that responsibility for the execution of state policy towards blacks resident in urban areas was removed from the Eastern Cape municipalities and vested in the newly created Cape Midlands Administration Board. The Board's boundaries were announced in December 1972 after the recommendations of the Bantu Affairs Administration Boards Implementation Advisory Committee and were to consist of the magisterial districts of Port Elizabeth, Uitenhage, Kirkwood, Somerset East, Cradock, Bedford, Adelaide, Fort Beaufort, Stockenstrom, Victoria East, Albany, Bathurst, and Alexandria. The head office was based in Port Elizabeth. These boundaries remained unaltered until the amalgamation of the three administration boards in the greater Eastern Cape, Border and Karoo areas in 1979. Although the administration boards were to be primarily concerned with the administration of urban areas, they were also given responsibility for the administration of other aspects of policy towards blacks living in rural areas. Thus the Cape Midlands Administration Board estimated in 1973 that 327 601 persons were resident in the 20 urban areas within its jurisdiction while 163 312 blacks lived in the rural non-prescribed areas. This was a total of 490 913 persons. , Digitised by Rhodes University Library on behalf of the Institute of Social and Economic Research (ISER)
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  • Date Issued: 1982

An investigation into the taxonomy of the diatoms (Bacillariophyta) of the Sundays and Great Fish Rivers, with ecological observations on the Sundays River

  • Authors: Archibald, Robert Eldred Mostert
  • Date: 1982
  • Subjects: Diatoms -- South Africa -- Eastern Cape Diatoms -- Classification Aquatic ecology -- South Africa -- Eastern Cape -- Sundays River
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:4180 , http://hdl.handle.net/10962/d1003728
  • Description: This report on the diatoms (Bacillariophyta) of the Sundays and Great Fish rivers is divided into two sections. In Volume 1 the taxonomy of the diatoms from these two river systems is examined. A total of 331 taxa were studied, of which 5 are described as new species. Two taxa are given new names, since they were previously known under later homonyms. Twenty seven taxa were recorded for the first time from South Africa, while a number of species are given amended descriptions in the light of fresh information obtained concerning them. A few taxa (chiefly South African forms) have been united with previously described taxa. For the remainder of the taxa mentioned in the text, comments are passed with regard to their taxonomy and dimensions, based on facts gained through literature surveys and personal observations of the relevant taxa. As far as possible all taxa examined in Volume 1 are illustrated, and these illustrations are presented in Volume 3 of this study. Volume 2 deals with the ecology of the diatoms in the Sundays River. Special emphasis is laid on relating the composition of the diatom associations at the selected stations to the ambient salinity and ionic composition of the water. A new index, the Salinity Tolerance Index (STI), is proposed to summarize by means of a numerical value the information obtained from the analysis of a diatom association with respect to the character of the component taxa, and to indicate whether the association is derived from a freshwater, brackish water or marine source. The efficacy of the STI is evaluated in the text. The effect of the geological formations of the Sundays River valley and the underground waters emanating from them is discussed in the text. The consequences of a severe drought in the lower Sundays River, including hypersaline water in the upper estuary, on the diatom flora are also investigated.
  • Full Text:
  • Date Issued: 1982

Aye Maria = Aye Maria

Banele Song

Catholic mass hymn

Catholic mass hymn

Catholic mass hymn

Catholic mass hymn

Catholic mass hymn

Catholic mass hymn

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