Abstract
The paracalanid copepod,Bestiolina amoyensis, is a widely distributed species occurring in subtropical inshore waters across the Pacific Ocean. Its small size, herbivorous feeding habit, and high adaptability make the species one of the most promising candidates as potential live feed for hatchery larval rearing. This study investigated effects of different feeding density of microalgaeIsochrysisspp. (1 × 105, 2 × 105, 3 × 105, 4 × 105, and 5 × 105cells ml–1) and photoperiod (8L:16D, 12L:12D, and 16L:8D) on productivity-related parameters, including egg production, female life expectancy and population dynamics ofB. amoyensis. Results showed that total egg output over female lifespan, final population size and intrinsic rate of population of 12L:12D photoperiod treatments were always the highest among three photoperiod conditions, especially at the food concentration of 4 × 105cells ml–1, indicatingB. amoyensishad high reproductive performance and the population was in a more stable status. The number of nauplii from 4 × 105cells ml–1algal concentration treatment accounted for 75% of the population, and the ratio of females to males approaching 1:1 when photoperiod was 12L:12D; female life expectancy was 10.5 ± 0.6 days. In conclusion, our results showed thatIsochrysisspp. is a suitable feed forB. amoyensiswith an optimal concentration at 4 × 105cells mL–1; the optimal photoperiod forB. amoyensisrearing is 12L:12D. The relatively long reproductive lifespan and high intrinsic population increase rate makeB. amoyensisa good candidate to develop culture techniques for hatchery larval rearing.
Highlights
Providing palatable nutritional food of appropriate size to marine larvae at different development stages is one of the most challenging tasks in marine hatcheries
Under all 3 photoperiods tested, the total egg production over female lifespan increased continuously with increasing food concentration, and reached a peak at 4 × 105 cells ml−1 (p < 0.05), the trend reversed as microalgae concentration further increased to 5 × 105 cells ml−1 (p < 0.05, Figure 2)
Photoperiod had a significant effect on the total egg production of female at various food concentrations (p < 0.001): At microalgae concentration of 3 × 105, 4 × 105, and 5 × 105 cells ml−1, the highest egg production was all found under the photoperiod of 12 h L:12hD, followed by the photoperiod of 8 h L: 16 h D, while the 16 h L:8 h D photoperiod always had the lowest egg production (Figure 2)
Summary
Providing palatable nutritional food of appropriate size to marine larvae at different development stages is one of the most challenging tasks in marine hatcheries. Food and Photoperiod on Bestiolina amoyensis ingested by them (Fielder et al, 2000; Assavaaree et al, 2003; Gopakumar and Santhosi, 2009; Wullur et al, 2009; Conceição et al, 2010; Lindley et al, 2011; Hagiwara et al, 2014), and lacking of appropriate live prey to feed such larvae has been a crucial technical bottleneck. Copepods are the natural food for most marine larvae and nauplii of many copepods are less than 100 μm in size, which can meet the first feeding requirement of even small mouth- gaped fish larvae (McKinnon et al, 2003; Camus and Zeng, 2010; Bradley et al, 2013; Hill et al, 2020). No attempts have been made to culture the species as the live prey for feeding fish larvae previously
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