Browsing by Author "Viljoen, Mauritz Johann"
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- ItemDetermining production characteristics of dusky kob, Argyrosomus japonicus, grown in sea cages under commercial conditions in Richards Bay, South Africa(Stellenbosch : Stellenbosch University, 2019-04) Viljoen, Mauritz Johann; Hoffman, Louwrens C.; Salie, Khalid; Stellenbosch University. Faculty of Agrisciences. Dept. of Animal Sciences.ENGLISH ABSTRACT: With aquaculture in South Africa being in its infancy there are many questions regarding the production characteristics of potential candidate aquaculture species, one such species being the dusky kob (Argyrosomus japonicus). Production results were obtained from the DST SU KZN Aquaculture Development Project that was implemented and managed by Stellenbosch University from 2015 to 2017 in Richards Bay, KwaZulu-Natal. The project assessed the technical, environmental and financial feasibility of farming dusky kob in sea cages. In August 2015, 25000 dusky kob fingerlings of 9 grams each were stocked into the cages. Two size classes emerged in the growth trial; the fish reached average weights of 1580 grams and 1082 grams respectively. Total FCR calculated over the course of the production period (23 months) was 2.25 at an average water temperature of 21°C. Fish size had no effect on fillet yield (%), but had a significant effect on fillet proximate composition. As fish size increased, lipid content increased and moisture content decreased. Initially, protein content increases as fish grew in size, although the rate of increase also declined. Using a copper alloy net cage to farm marine fish in an attempt to reduce or eliminate biofouling caused no significant difference in metal concentrations in meat samples derived from fish grown in traditional polyester versus copper alloy net cages. The maximum concentrations measured for the various metals in meat samples were below the upper limits as set by South African, EU and USA regulations for safe human consumption. A summary of harvesting methods used to harvest dusky kob from sea cages and the subsequent logistical cold chain, as well as general observations and recommendations regarding the production of dusky kob is provided.