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, W 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
Metabolic activity throughout early development of dusky kob Argyrosomus japonicus (Sciaenidae)
- Authors: Edworthy, Carla , James, Nicola C , Erasmus, B , Kemp, J O G , Kaiser, Horst , Potts, Warren M
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/125159 , vital:35737 , https://doi.10.2989/1814232x.2018.1441907
- Description: Metabolism quantifies the energy-consuming activities of an organism (Nelson 2016) and is used as an indication of how organisms partition energy resources to activities that allow them to survive, grow and reproduce (Post and Lee 1996). The metabolic profile, which is a composition of the various metabolic rates of an individual, therefore gives an indication of the efficiency of energy transformation and allocation (Fry 1971; Brown et al. 2004). McKenzie et al. (2016) suggested that an organism’s physiology contributes towards its ability to survive under specific environmental conditions. As a result, physiological condition can be a reflection of the performance and fitness of an organism (Pörtner 2010). When combined with information on changing environmental conditions, physiological information can provide insight into species- and community-level responses (Pörtner and Farrell 2008). These kinds of data have served numerous ecological applications, including resource management, conservation (McKenzie et al. 2016) and climate-change assessments (Pörtner and Farrell 2008).
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- Date Issued: 2018
Influence of intra-and interspecific variation in predator–prey body size ratios on trophic interaction strengths:
- Authors: Cuthbert, Ross N , Wasserman, Ryan J , Dalu, Tatenda , Kaiser, Horst , Weyl, Olaf L F , Dick, Jaimie T A , Sentis, Arnaud , McCoy, Michael W , Alexander, Mhairi E
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/149358 , vital:38839 , https://0-doi.org.wam.seals.ac.za/10.1002/ece3.6332
- Description: Predation is a pervasive force that structures food webs and directly influences ecosystem functioning. The relative body sizes of predators and prey may be an important determinant of interaction strengths. However, studies quantifying the combined influence of intra‐ and interspecific variation in predator–prey body size ratios are lacking. We use a comparative functional response approach to examine interaction strengths between three size classes of invasive bluegill and largemouth bass toward three scaled size classes of their tilapia prey. We then quantify the influence of intra‐ and interspecific predator–prey body mass ratios on the scaling of attack rates and handling times.
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- Date Issued: 2020