A life-history approach to the early ontogeny of the Mozambique tilapia Oreochromis mossambicus (Pisces, Cichlidae)
- Authors: Holden, Kathleen K , Bruton, Michael N
- Date: 1992
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447116 , vital:74585 , https://www.ajol.info/index.php/az/article/view/154193
- Description: The early ontogeny of Oreochromis mossambicus (Peters) was followed from the time of egg activation until the juvenile period. Development is direct and consists of an embryonic period of approximately 15 days. The embryonic period can be divided into a cleavage, an embryonic and a free-embryonic phase. A detailed developmental description is given and the relationship between the early ontogeny and the early life-history pattern is examined. The terminology used for the last step of the free-embryonic phase and a possible truncated larval period is discussed.
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- Date Issued: 1992
The distribution of the Wattled Starling in southern Africa
- Authors: Craig, Adrian J F K
- Date: 1992
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447896 , vital:74682 , https://doi.org/10.1080/00306525.1992.9634180
- Description: Dated distribution records of the Wattled Starling Creatophora cinerea have been assembled from the literature, museum specimens, atlas records, and other unpublished observations. The bulk of these records are from the period 1980–89. Breeding records are sparse, but breeding appears to be seasonal in the winter rainfall area. In summer rainfall areas nesting occurs from spring through to autumn, dependent on the presence of abundant insects. In most areas winter records (June to August) predominate, but in the eastern lowveld areas of South Africa Wattled Starlings are recorded most often in spring and summer. The species is correctly described as nomadic, and the pattern of occurrence does not suggest regular migration.
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- Date Issued: 1992
Turbidity-induced changes in feeding strategies of fish in estuaries
- Authors: Hecht, Thomas , Van der Lingen, C D
- Date: 1992
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/446960 , vital:74573 , https://hdl.handle.net/10520/AJA00445096_644
- Description: The aim of this study was to determine the effect of turbidity on the feeding strategies of fish in estuaries. Three species representing different feeding guilds were selected for the investigation. These were Elops machnata (representative piscivore), Pomadasys commefsonnii (a macrobenthivore) and Athefina breviceps (a planktivore). The stomach contents of these fish were examined from a clear and a turbid estuary and some experimental work was carried out on A. brevic8ps to test the hypothesis that turbidity affects feeding behaviour. Turbidity was found to have no effect on size selection of prey, but feeding rate, particularly of visual predators, was reduced at higher turbidity levels. This was caused by a decrease in the reactive distance of the fish. It would appear that in order to optimize the aquisition of food under different turbidity conditions fishes have the ability to change their feeding strategies. Visual predators are more affected by turbidity than are macrobenthic feeders.
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- Date Issued: 1992