- Title
- Population structure, production, growth, reproduction and the ecology of Atherina breviceps Valenciennes, 1935 (Pisces : Atherinidae) and Gilchristella aestuaria (Gilchrist, 1914) (Pisces : Clupeidae), from two southern Cape coastal lakes
- Creator
- Ratte, Theodore Wilhlelm
- Subject
- Silversides
- Subject
- Clupeidae -- South Africa -- Cape of Good Hope
- Date Issued
- 1989-01
- Date
- 1989-01
- Type
- Doctoral theses
- Type
- text
- Identifier
- http://hdl.handle.net/10948/50878
- Identifier
- vital:43029
- Description
- Over the period October 1978 to January 1981, a total of 147 853 Atherina breviceps with a total biomass of 55 2B0,7 g and 107 046 Gilchristella aestuaria with a total biomass of 33 708,9 g were collected in the Swartvlei System and 151 531 A. breviceps with a total biomass of 727 795,0 g and 51 258 G. aestuaria with a total biomass of 12 231,5 g were collected in Groenvlei, to determine their population structure, production, growth, reproduction and ecology in both systems. A. breviceps and G. aestuaria were collected from nine and eleven estuaries respectively, including Groenvlei, along the Cape coast to determine the degree of genetic divergence of both these two species in Groenvlei. It was found that the mature 0-year-old A. breviceps and the 2-year-old G. aestuaria dominated the catches in the Swartvlei System, whereas the juvenile 0-year-olds and 1-year-olds of both species respectively, dominated the catches in Groenvlei. The Swartvlei System and Groenvlei produced respectively between 10-12 metric tons of A. breviceps and between 5-3 metric tons of G. aestuaria annually. A. breviceps and G. aestuana in the Swartvlei System and Groenvlei attain observed ages of between 3 years and 7-8 years respectively. The main spawning period for both species is between spring-autumn in Groenvlei and for A. breviceps in the Swartvlei System. G. aestuaria has a continuous winter-summer spawning in the Swartvlei System. A. breviceps and G. aestuaria in Groenvlei have diverged to such an extent from these two species' populations in other systems, that A. breviceps and G. aestuaria in Groenvlei should receive a priority conservation status.
- Description
- Thesis (PhD) -- Faculty of Science, 1989
- Format
- computer
- Format
- online resource
- Format
- Format
- 1 online resource (339 pages)
- Publisher
- University
- Publisher
- Faculty of Science
- Language
- English
- Rights
- Nelson Mandela University
- Rights
- All Rights Reserved
- Rights
- Open Access
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| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | SOURCE1 | Ratte Theodor Wilhelm.pdf | 12 MB | Adobe Acrobat PDF | View Details Download |