High genetic diversity and limited spatial structure in an endangered, endemic South African sparid, the red steenbras Petrus rupestris:
- Authors: Gouws, Gavin , Kerwath, S E , Potts, Warren M , James, Nicola C , Vine, Niall G , Cowley, Paul D
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/160379 , vital:40440 , DOI: 10.2989/1814232X.2020.1788640
- Description: The red steenbras Petrus rupestris is endemic to South Africa, occurring from False Bay in the Western Cape Province to St Lucia in the province of KwaZulu-Natal. This species, the largest member of the family Sparidae, has undergone a substantial stock decline as a result of overfishing and is considered to be collapsed. Various aspects of its life history, including high residency, predictable migrations, late maturity and longevity, have made it vulnerable to overexploitation. This study analysed the diversity and genetic structure of red steenbras across seven sampling regions, using mitochondrial (control region) and nuclear (S7 intron 1) DNA markers.
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- Date Issued: 2020
The effect of different dietary microalgae on the fatty acid profile, fecundity and population development of the calanoid copepod Pseudodiaptomus hessei (Copepoda: Calanoida)
- Authors: Siqwepu, Oyama , Richoux, Nicole B , Vine, Niall G
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/456318 , vital:75502 , xlink:href="https://doi.org/10.1016/j.aquaculture.2016.10.008"
- Description: We studied the effect of dietary microalgae on the fecundity, population development, and fatty acid profile [with focus on the essential fatty acids docosahexaenoic acid (DHA; 22:6ω3) and eicosapentaenoic acid (EPA; 20:5ω3)] of the calanoid copepod Pseudodiaptomus hessei, a potential live food for finfish larvae in aquaculture. Two mono-algal diets, the Tahitian strain of Isochrysis galbana and Rhodomonas salina, and a 50:50 binary diet of the two were fed to copepods. Wild caught copepods were used as a baseline reference point. Copepods fed I. galbana and the 50:50 binary diet had high DHA:EPA ratios and DHA content relative to those fed R. salina. The EPA content of the copepods was similar for all three diets. Copepods fed R. salina had the highest fecundity relative to those fed I. galbana and the 50:50 binary diet. The largest population was obtained when the copepods were fed I. galbana, which differed from those fed R. salina and the 50:50 binary diet. The results of this study showed that the fatty acid composition of P. hessei can be altered by changing its dietary microalgae, and that the copepod can accumulate fatty acids from its diet, especially DHA and EPA. Diet also affected fecundity and population development of P. hessei, so this species represents a potential live food candidate for marine finfish larvae as its nutritional composition and productivity can be manipulated to suit the needs of marine finfish larvae.
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- Date Issued: 2017
Determination of the optimal water temperature for the culture of juvenile dusky kob Argyrosomus japonicus Temminck and Schlegel 1843:
- Authors: Collett, Paul D , Vine, Niall G , Kaiser, Horst , Baxter, Jeremy
- Date: 2008
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/142804 , vital:38118 , DOI: 10.1111/j.1365-2109.2008.01960.x
- Description: The effects of temperature on growth, food conversion ratio (FCR) and feeding intensity of juvenile dusky kob Argyrosomus japonicus (23.7±2.6 g fish−1) were assessed over the temperature range 17.5–28.5°C in a 42 day growth trial. Growth increased with increasing temperature up to an optimum after which it declined. Specific growth rates were 2.05% and 1.2% day−1 for the fastest (25.3 °C) and the slowest (17.5 °C) treatments respectively. Food conversion ratio peaked at a lower temperature than growth. Optimal (0.72 kg kg gain−1) and least efficient (1.40 kg kg gain−1) FCR were found at 21.7 and 17.5°C respectively. Feeding intensity was linearly related to temperature within the range of 17.5–28.5°C. These results corresponded to the thermal preference (25–26.4°C) and natural temperature distribution (12–28°C) of South African dusky kob. Determination of the temperature range that does not limit growth is a prerequisite to assess the relationship between growth and environmental variables such as light intensity, feeding regime and stocking density. Consequently, experiments to determine the effects of these environmental variables on growth and aquaculture potential of dusky kob should be conducted at 24–26°C.
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- Date Issued: 2008
Competition for attachment of aquaculture candidate probiotic and pathogenic bacteria on fish intestinal mucus:
- Authors: Vine, Niall G , Leukes, Winston D , Kaiser, Horst , Daya, Santylal , Baxter, Jeremy , Hecht, Thomas
- Date: 2004
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/142819 , vital:38120 , DOI: 10.1111/j.1365-2761.2004.00542.x
- Description: Probiotics for aquaculture are generally only selected by their ability to produce antimicrobial metabolites; however, attachment to intestinal mucus is important in order to remain within the gut of its host. Five candidate probiotics (AP1–AP5), isolated from the clownfish, Amphiprion percula (Lacepéde), were examined for their ability to attach to fish intestinal mucus and compete with two pathogens, Aeromonas hydrophila and Vibrio alginolyticus. Two different radioactive isotopes were used to quantify competition between pathogens and probionts. Attachment of the pathogens was enhanced by the presence of the candidate probiotics. However, the addition of the candidate probiotics after the pathogens resulted in reduced pathogen attachment.
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- Date Issued: 2004