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Visual acuity of snapper Pagrus auratus: effect of size and spectral composition

Authors

  • E. Robinson,

    Corresponding author
    1. School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch, New Zealand
    2. The New Zealand Institute for Plant & Food Research Limited, Seafood Production, PO Box 5114, Port Nelson, Nelson, New Zealand
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  • A. R. Jerrett,

    1. The New Zealand Institute for Plant & Food Research Limited, Seafood Production, PO Box 5114, Port Nelson, Nelson, New Zealand
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  • S. E. Black,

    1. The New Zealand Institute for Plant & Food Research Limited, Seafood Production, PO Box 5114, Port Nelson, Nelson, New Zealand
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  • W. Davison

    1. School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch, New Zealand
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Tel.: +64 3366 7001 ext. 4848; email: esme.robinson@canterbury.ac.nz

Abstract

Visual acuity of the commercially important sparid Pagrus auratus was tested using the optomotor response. Juvenile fish were categorized by size as group 1 (50 g), group 2 (100 g), group 3 (150 g), group 4 (300 g), group 5 (500 g) and group 6 (800 g). Group 3 fish demonstrated excellent visual acuity (minimum separable angle, MSA, 1°), which was improved compared with the smaller fish groups (groups 1 and 2, MSA, 2°). In the larger fish groups, however, a reduction in visual acuity was observed (groups 4, 5 and 6 MSA, 4°). Group 2 (100 g) fish displayed positive optomotor responses in long wavelength light (red) but reduced responses in short wavelengths (blue). Red light sensitivity is beneficial for the estuarine lifestyle of these fish, where light is predominantly at long wavelengths. In contrast, group 6 (800 g) fish displayed improved acuity in blue and green light and reduced acuity in red light. Fish of this size move away from the estuary to open oceans, where light is predominantly in the shorter wavelengths (blue-green). These results support the sensitivity hypothesis for the relationship between fish visual systems and the light environment they inhabit.

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