West Beach, Australia
West Beach, Australia

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Balshaw S.,Flinders University | Balshaw S.,South Australian Research And Development Institute | Balshaw S.,Aquafin Cooperative Research Center | Ellis D.,Aquafin Cooperative Research Center | And 2 more authors.
Aquaculture | Year: 2011

A model is presented for the prediction of mercury (Hg) concentrations in the edible tissues of farmed southern bluefin tuna, Thunnus maccoyii (SBT) during commercial culture. The predictive model was developed using the initial Hg concentration of wild-caught SBT (mgkg -1), Hg concentration of feed (mgkg -1), SBT feeding rate (kgkg -1day -1), SBT tissue growth rate (kgday -1) and least squares minimisation estimation of Hg uptake efficiency, η. Model development and validation was based on experimental data collected from commercially cultured SBT which are farmed in in-sea pontoons (sea-pontoons). Model predictions indicate that over a typical farming season SBT from each of three commercially operated sea-pontoons experienced a 0.1mgkg -1, 0.14mgkg -1 and >0.2mgkg -1 reduction in the Hg concentration of muscular tissues respectively. This is the first study to attempt to estimate Hg uptake efficiency in a tuna species. Estimation of Hg uptake efficiency and development of a working model for prediction of Hg concentration in SBT under varying culture diets, represent the first steps towards taking the guesswork out of managing Hg residues in cultured tuna. © 2011 Elsevier B.V.

Musgrove R.J.,SARDI Aquatic Sciences Center | Musgrove R.J.,Aquafin Cooperative Research Center | Carragher J.F.,SARDI Aquatic Sciences Center | Carragher J.F.,Aquafin Cooperative Research Center | And 8 more authors.
Aquaculture Nutrition | Year: 2011

Feed nutritional quality impacts on the performance of aquacultured species. This study was undertaken to assess the consequences of existing postharvest handling practices on nutritional quality of local baitfish (Australian sardines, Sardinops sagax and redbait, Emmelichthys nitidus nitidus) used to feed farmed southern bluefin tuna (Thunnus maccoyii). Controlled experiments were then undertaken to determine the most appropriate postharvest treatments to maintain baitfish nutritional quality, assessed through measurement of vitamins C and E, histamine, K value and TBARS. During frozen storage (-18°C) vitamins and fish freshness decreased significantly and rancidity increased; after approximately 3months baitfish were of questionable utility, particularly as a source of antioxidants. On-land freezing method [i.e. block or individually quick frozen (IQF)] affected vitamin E loss with IQF sardines losing vitamin E faster than block-frozen baitfish. Block-frozen baitfish, particularly sardines, should be thawed in seawater, not air or freshwater, to minimize vitamin losses. Thawing time should be no more than 2days, and baitfish storage less than 3months. Thiobarbituric acid reactive substances (TBARS) correlated well with remaining vitamin E, indicating its usefulness as an indicator of antioxidant status. TBARS analysis is methodologically simpler, faster and cheaper than that for vitamins, and is therefore recommended for determination of baitfish nutritional quality. © 2010 SARDI Innovative Food and Plants.

Balshaw S.,Flinders University | Balshaw S.,South Australian Research And Development Institute | Balshaw S.,Aquafin Cooperative Research Center | Edwards J.W.,Flinders University | And 4 more authors.
Food Chemistry | Year: 2012

The docosahexanoic acid (DHA) and eicosapentaenoic acid (EPA) contents and total mercury concentration were measured in whole tissue composites of all edible tissues of wild caught and farmed southern bluefin tuna (Thunnus maccoyii, SBT) and each of the marketed tissue cuts (akami, chu-toro and o-toro) of these fish. Rapid lipid accumulation during culture resulted in a net reduction in mercury concentration of SBT composite tissues and an increase in the concentration of the dietary essential fatty acids. Moreover, the increased affinity of lipid for certain tissue cuts (o-toro) over that of others (e.g. akami), resulted in cross carcass variation in the mercury concentration of fish muscular tissue. Results highlight the potential for farming to be used as a tool to improve the flesh quality of fish species which could otherwise provide limited dietary essential fatty acids to consumers and potentially contain elevated contaminant levels. © 2011 Elsevier Ltd. All rights reserved.

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