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¹ University of the Ryukyus, Graduate School of Engineering and Sciences, 1 Senbaru, Nishihara, Okinawa 903-0213, Japan
² University of the Ryukyus, Department of Chemistry, Biology and Marine Science, Faculty of Science, 1 Senbaru, Nishihara, Okinawa 903-0213, Japan DOI : 10.4194/1303-2712-v19_11_03 Viewed : 3282 - Downloaded : 2912 Fish growth is influenced by photic environments, including light intensity, cycle (photoperiod), and wavelength. Here, we investigated the effects of photic conditions on somatic growth of the juvenile goldlined spinefoot Siganus guttatus. Rearing 3- and 11-month-old juveniles under three different light intensities (10%, 0.5–1.0%, and < 0.1% of natural sunlight at culmination) for 8 weeks resulted in little difference in the growth parameters of individuals (specific growth rate [SGR] and condition factor [CF]). High SGR was observed in 4-month-old juveniles reared under constant light (LL) and long-day (LD=14:10), but not under short-day (LD=10:14), for 8 weeks, and in 1- and 9- month-old juveniles exposed to long-day of green LED lights for 4 and 8 weeks, respectively. Real-time quantitative PCR revealed that mRNA abundance of growth hormone in the pituitary and insulin-like growth factor-I in the liver increased in the juveniles reared under long-day, suggesting that the endocrine axis is stimulated under this condition. Thus, somatic growth of the juveniles can be manipulated by alternating the photoperiod and light wavelength. Finally, growth manipulation is more effective in younger fish. Keywords : Goldlined spinefoot, Growth rate, Light-emitting diodes, Photoperiod, Rabbitfish