The effects of continuous photoperiod (24L:0D) on growth of juvenile barramundi (<Emphasis Type="Italic">Lates calcarifer</Emphasis>) |
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Authors: | K L Worrall C G Carter R J Wilkinson M J R Porter |
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Institution: | (1) National Centre for Marine Conservation and Resource Sustainability, University of Tasmania, Locked Bay 1370, Launceston, TAS, 7250, Australia;(2) Ridley Aquafeed Pty Ltd, 12 Neon Street, Narangba Brisbane, QLD, 4504, Australia; |
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Abstract: | The efficacy of photoperiod manipulation to influence growth and developmental processes is well documented in a range of
temperate aquaculture species. However, the application of such techniques with tropical species requires further investigation.
This preliminary 20-day study investigated the influence of continuous photoperiod on growth of barramundi (Lates calcarifer). In addition, diel plasma melatonin profiles provided a physiological measure of how the endocrine system of barramundi
responded to continuous photoperiod. Juvenile barramundi (1.33 ± 0.02 g) were held in recirculation systems under 12-h light:
12-h dark (12L:12D) or 24-h light (24L:0D) with a light intensity of 1,000 lux throughout the water column. Fish from both
treatments grew to more than 14 times their original weight, with final weight (24L:0D = 21.59 ± 0.85 g; 12L:12D = 19.12 ± 0.55 g),
total length (24L:0D = 12.67 ± 0.14 cm; 12L:12D = 11.96 ± 0.13 cm) and specific growth rate (24L:0D = 9.60 ± 0.05% bw day−1; 12L:12D = 9.14 ± 0.06% bw day−1) being significantly higher for fish grown on 24L:0D compared with 12L:12D. There were no significant differences in feed
intake (24L:0D = 226.46 ± 6.27 g; 12L:12D = 219.02 ± 5.73 g) or feed conversion ratio (24L:0D = 0.71 ± 0.06; 12L:12D = 0.80 ± 0.07)
between light treatments. Barramundi held under 12L:12D exhibited diel melatonin secretion, which peaked mid-dark phase (171.83 ± 4.81 pg ml−1) followed by a gradual decrease in base levels at the onset of illumination (68.61 ± 8.77 pg ml−1). When juvenile barramundi were subjected to 24L:0D, the amplitude of peak melatonin secretion was significantly suppressed
during the subjective mid-dark phase (129.71 ± 2.36 pg ml−1). This preliminary study confirmed that barramundi respond to photoperiod manipulation in a similar manner to many temperate
fish species, thus demonstrating the future potential use of artificial lighting to improve growth in this species commercially. |
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