Effect of temperature and photoperiod on the growth, feed consumption, and biochemical content of juvenile green abalone, Haliotis fulgens, fed on a balanced diet

Juvenile green abalone, Haliotis fulgens (31.3 ± 0.1 mm, 3.7 ± 0.04 g live weight) were reared in laboratory for six months in order to determine their survival, growth, tissue composition, feed consumption (C), feed conversion ratio (FCR) and protein efficiency ratio (PER) under two temperatures (20 °C and 25 °C) and three photoperiods (00:24, 12:12 and 24:00 light:dark hours). Survival was ca. 100% at 20 °C, and between 68% and 75% at 25 °C. The highest gross growth rate (109 ± 4.3 μm d− 1, 69 ± 3.9 mg d− 1) was observed in abalone from the combination 20 °C–00:24 L:D. Slowest GGR (38 ± 4.1 μm d− 1, 26 ± 1.5 mg d− 1) was observed in the combination 25 °C–24:00 L:D. Organisms from 25 °C exhibited signs of the withering syndrome at the end of the experiment. Gross energy content (4.4 to 4.6 kcal g− 1 tissue dry wt, TDW) and crude protein (60 to 68% TDW) were not significantly affected by either temperature or photoperiod, but organisms from 20 °C exhibited lower moisture content (86.8 to 88.6%) and higher tissue:shell ratio (0.34–0.40) than those from 25 °C (88.9 to 92.1%; 0.22–0.31 respectively). Feed consumption markedly increased at night, decreased with age, and was higher at 25 °C than 20 °C, irrespective of photoperiod. Highest C was observed under continuous darkness (0.66 to 0.95% BW d− 1 at 20 °C and 0.84 to 1.25% BW d− 1 at 25 °C), and was lowest under continuous light (0.50 to 0.82% BW d− 1 at 20 °C and 0.71 to 1.02% BW d− 1 at 25 °C). FCR and PER were both affected by temperature but not by photoperiod. Higher PER (2.2 to 3.4) and lower FCR values (0.69 to 1.05) were observed at 20 °C, when compared to 25 °C (PER 1.35 to 2.09, FCR 1.10 to 1.86). Sex ratios were ca. 1:1 in the 00:24 and 12:12 L:D photoperiods, yet ca. 50% of abalone from the 24:00 L:D photoperiod were immature at the end of the experiment. It is concluded that H. fulgens can be best cultured at 20 °C and 00:24 or 12:12 L:D regimes, while sustained temperatures at or above 25 °C may result in cumulative stress, altered physiological rhythms, and delayed maturation.