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
- 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
The life history of a minnow, Barbus Anoplus, in a man-made lake in South Africa
- Authors: Cambray, James Alfred
- Date: 1982
- Subjects: Minnows -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5346 , http://hdl.handle.net/10962/d1006861
- Description: Aspects of the life history strategy of Barbus anoplus Weber were studied in a turbid man-made lake (P.K. Ie Roux impoundment, Orange River system, South Africa). The minnow has successfully colonized the shoreline of the P.K. Ie Roux impoundment, where the preferred habitats of the chubbyhead barb are flooded stream beds, erosion gullies and flooded ruderal communities. B. anoplus reaches sexual maturity in one year, at a length of about 40mm FL. They have a multiple spawning habit, with the first spawn in November or December and the second spawn in February or March. A part of the adult population undertakes a spawning migration up inflowing tributaries, while the other part breeds along the shoreline. The eggs and young develop rapidly and a proportion of the protolarvae float near the water surface, where they are probably dispersed by water currents. Most of the males die off after their second summer, whereas many females live into a third summer. Females also attain a larger maximum size (73mm FL) than males (60mm FL). The importance of increasing the reproductive potential of B. anoplus by multiple spawning is discussed. Feeding studies indicate that B. anoplus are opportunistic predators on invertebrates. The feeding habits of minnows collected from four different habitats varied. Minnows collected in the open water fed mainly on zooplankton, while shoreline populations fed on chironomid larvae and zooplankton. The most varied diet was found in fish living in a well-vegetated tributary of the impoundment which was not subject to inundation. B. anoplus is basically an r-strategist (i.e. it is small in size, shortlived, males have bright colouration, high seasonal reproductive potential). These characteristics enable the species to colonize and successfully inhabit unstable environments and probably accounts for the fact that it is the most widespread species south of the Limpopo River system. It is recommended that B. anoplus be considered as a candidate in southern Africa for further studies on life history strategies.
- Full Text:
- Date Issued: 1982
- Authors: Cambray, James Alfred
- Date: 1982
- Subjects: Minnows -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5346 , http://hdl.handle.net/10962/d1006861
- Description: Aspects of the life history strategy of Barbus anoplus Weber were studied in a turbid man-made lake (P.K. Ie Roux impoundment, Orange River system, South Africa). The minnow has successfully colonized the shoreline of the P.K. Ie Roux impoundment, where the preferred habitats of the chubbyhead barb are flooded stream beds, erosion gullies and flooded ruderal communities. B. anoplus reaches sexual maturity in one year, at a length of about 40mm FL. They have a multiple spawning habit, with the first spawn in November or December and the second spawn in February or March. A part of the adult population undertakes a spawning migration up inflowing tributaries, while the other part breeds along the shoreline. The eggs and young develop rapidly and a proportion of the protolarvae float near the water surface, where they are probably dispersed by water currents. Most of the males die off after their second summer, whereas many females live into a third summer. Females also attain a larger maximum size (73mm FL) than males (60mm FL). The importance of increasing the reproductive potential of B. anoplus by multiple spawning is discussed. Feeding studies indicate that B. anoplus are opportunistic predators on invertebrates. The feeding habits of minnows collected from four different habitats varied. Minnows collected in the open water fed mainly on zooplankton, while shoreline populations fed on chironomid larvae and zooplankton. The most varied diet was found in fish living in a well-vegetated tributary of the impoundment which was not subject to inundation. B. anoplus is basically an r-strategist (i.e. it is small in size, shortlived, males have bright colouration, high seasonal reproductive potential). These characteristics enable the species to colonize and successfully inhabit unstable environments and probably accounts for the fact that it is the most widespread species south of the Limpopo River system. It is recommended that B. anoplus be considered as a candidate in southern Africa for further studies on life history strategies.
- Full Text:
- Date Issued: 1982
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