Browsing by Subject "Aquaculture"

Now showing 1 - 5 of 5
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    Bioenergetics and growth of white steenbras, Lithognathus lithognathus, under culture conditions
    (1991) Harris, Shael Anne; Cook, Peter
    The bioenergetics and growth of white steenbras, Lithognathus lithognathus, under culture conditions were determined to assess its suitability for mariculture. Fish were captured by seine netting, from nearby estuaries and transported to the laboratory where they were successfully kept for the duration of the experimental period. The fish were initially fed on white mussels and then weaned onto a diet of commercial trout pellets. The bioenergetics of L.lithognathus was examined using a large, simple closed system respirometer in which nitrogen excretion and oxygen consumption were measured simultaneously. This system permitted the use of groups of fish for experiment which simulated aquaculture conditions. The effects of fish size, ration size and temperature on faecal and nonfaecal excretion, and on oxygen consumption of L.lithognathus were examined.
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    Can the pathway of abalone aquaculture effluent be traced using carbon and nitrogen stable isotope analysis of kelp Ecklonia maxima and mussels Mytilus galloprovincialis?
    (2007) Thomas, Alicia; Bolton, John J; Anderson, Robert J; February, Edmund C
    Abalone farms are becoming more common along the coast of South Africa. The effects these farms are having on the coastal habitats they occupy are becoming of increasing concern due to the possible negative effects of the effluent discharged from the farm. This study was conducted along the coast of Jacobsbaai (32°58'22.09" Sand 17°53'10.56" E) and Mauritzbaai (32°58'50.75"S and 17°52'59.44"E) near Saldanha on the South African west coast, situated approximately 120 Km from Cape Town. The aim of this study is to determine if the outflow of effluent from the Jacobsbaai Sea Products (pty) Ltd, abalone farm in Jacobsbaai can be traced using stable carbon and nitrogen isotopes. Kelp (Ecklonia maxima) and blue mussels (Mytilus galloprovincialis) along the coast near the farm (in Jacobsbaai) were collected from 8 sites and used as tracers of the farms effluent. A ninth site was sample in another bay (Mauritzbaai) which functioned as our control. We hypothesised that if the kelp and mussels are taking up the nitrogen and carbon from the farm, the amount of nitrogen and carbon taken up would decrease with decreasing distance from the effluent outfall. Using this we could map the geographic distribution of the abalone effluent alone the coast to measure the extent of eutrophication due to abalone effluent. Our results suggest that the effluent from the farm is having a localized effect on both Ecklonia maxima and Mytilus galloprovincialis.
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    Chemosensory properties of different Ulva extracts and their effects on Tripneustes gratilla
    (2014) Du Plessis, Darren Scott; Cyrus, Mark Digby; Bolton, John J; Macey, Brett M
    Identifying the chemical compounds that attract urchins to seaweeds will increase sea urchin aquaculture efficiency as these compounds can be utilized in the production of artificial feeds enhancing their attractiveness and palatability. This study investigated the chemosensory preferences of the tropical sea urchin Tripneustes gratilla for four crude extracts of Ulva as well as Fresh Ulva and an artificial feed. The four crude extracts of Ulva (Methanolic, Ethanolic, Chloroform and Chloroform-Methanol extracts) were tested by pair-wise chemosensory trials in a Y shaped maze. Urchins were significantly deterred by both the Chloroform and Chloroform- Methanol extracts as well as the solvent controls and artificial feed, however T. gratilla was significantly attracted to both the Methanolic and Ethanolic extracts. These two extracts were tested individually against Ulva and the urchins could not distinguish between Ulva and the extracts. When these two extracts were tested against one another it was found that the urchins were significantly attracted to the Methanolic extract. The Methanolic extract was then added to the artificial feed and significantly improved the feeds attractability. This indicates that these extracts, or the compounds which are responsible for this effect, can be incorporated into artificial feeds thereby making them more attractive to the sea urchin. The percentage yield of Ulva that each solvent extracted was different, although only the Ethanolic extract was found to be significantly different from the Chloroform and Chloroform-Methanol extracts. Future studies are needed to examine the chemical composition of these specific chemosensory compounds. By incorporating these attractive extracts into artificial feeds, South Africa can potentially improve the cultivation success of T. gratilla therefore expanding the economy of the local aquaculture industry through the export of this highly valued seafood product.
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    Do we have the vision to integrate our marine aquaculture?
    (2006) Bolton, John J
    The article focuses on the author's views on marine aquaculture in South Africa. He discussed the draft policy for the development of a sustainable aquaculture industry in South Africa released by the Department of Environmental Affairs and Tourism. Statistics on African aquaculture production, geographical spread and species exploitation in acquaculture, and marine aquaculture consumption are provided. The author also gives reasons why aquaculture production is low in the country.
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    The nutritional effects of selected algae, prebiotics and commercial herbal feed additives on the growth rate and health of juvenile spotted grunter, Pomadasys commersonnii (Pisces: Haemulidae)
    (2017) Mbona, Anathi; Marco, Heather G; Fouche, Chris
    In the aquaculture of fish and shrimps, diets generally contain high levels of fish meal. Fish meal is a nutrient rich feed that contains essential amino acids and fatty acids, which are required to maintain optimum growth and health of an animal. It is traditionally used in aquaculture to promote feed efficiency, nutrient uptake and feed intake due to its high palatability and digestibility. Overexploitation of fisheries resources and the high growth rate of aquaculture industry, however, continues to put pressure on the supply of fish meal, thus increasing the demand and price of this sought-after product. The use of alternative ingredients to fish meal, therefore, remains a high priority for aquaculture nutrition. Hence, the aim of this was to investigate the physiological and developmental effects on juvenile spotted grunter, Pomadasys commersonnii, after supplementing fish meal with different feed additives for 12 weeks. One of the additives was then selected for further feeding at graded levels (increasing levels) for 8 weeks to ascertain whether fish meal could be replaced by higher amounts of the feed additive without negative consequences to the cultured spotted grunter.