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Interactive effects of food quality, temperature and rearing time on condition of juvenile black bream Acanthopagrus butcheri

Authors

  • B. D. Walther,

    Corresponding author
    1. Southern Seas Ecology Laboratories, School of Earth and Environmental Sciences, DX 650 418, University of Adelaide, Adelaide, South Australia 5005, Australia
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  • T. S. Elsdon,

    1. Southern Seas Ecology Laboratories, School of Earth and Environmental Sciences, DX 650 418, University of Adelaide, Adelaide, South Australia 5005, Australia
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  • B. M. Gillanders

    1. Southern Seas Ecology Laboratories, School of Earth and Environmental Sciences, DX 650 418, University of Adelaide, Adelaide, South Australia 5005, Australia
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Author to whom correspondence should be addressed at present address: Marine Science Institute, University of Texas at Austin, 750 Channel View Drive, Port Aransas, TX 78373, U.S.A. Tel.: +1 361 749 6810; fax: +1 361 749 6749; email: bwalther@mail.utexas.edu

Abstract

A laboratory experiment was conducted to determine the interactive effects of temperature and diet on condition indices of juvenile black bream Acanthopagrus butcheri, reared for time periods ranging from 2 to 42 days. After fish were reared for varying periods, growth, morphometric (Fulton's K) and biochemical [RNA:DNA (R:D) ratios] indices were measured. Fulton's K responded primarily to temperature, with progressive decrease in condition over time for fish reared at high temperatures. In contrast, R:D ratios were primarily affected by diet composition, with the highest values observed for fish reared on fish-based diets as opposed to vegetable-based diets. Significant effects of rearing time were also observed for Fulton's K and R:D ratios, as were some interactive treatment effects. In addition, Fulton's K and R:D ratios were not significantly correlated, perhaps due to the different periods of time integrated by each index or their relative sensitivity to lipid and protein deposition. These results highlight the complex responses of these condition indices to environmental variables and nutritional status.

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