| Summary: | 碩士 === 國立臺灣海洋大學 === 水產養殖學系 === 107 === The aim of this study was to optimize the artificial propagation of Caridina gracilirostris by sequential investigating the effects of (I) Sex ratio on the reproduction of adult shrimp; (II) Feed concentration on the survival rate of larvae; (III) Stocking density on the survival rate of larvae; (IV) Freshwater acclimation at different time points on the survival rate of postlarvae; (V) Stocking density on the growth and survival rate of postlarvae. Taken above results together, the optimal conditions of Caridina gracilirostris aquaculture could be established.
In experiment I, adult were reared in different sex ratios of female to male. The ovigerous rate were 56 ± 10 %, 56 ± 10 %, and 61 ± 10 % in group 3:1, 3:2, and 3:3, respectively. There was no significant difference in each group (p > 0.05); the production of larvae was 284.60 ± 45.48, 272.70 ± 45.58 and 303.09 ± 44.11. No significant difference was also shown in each group (p > 0.05).
In experiment II, Tetraselmis chui was used for feeding experiments with the three densities of 1 × 105 cells / mL, 1.5 × 105 cells / mL, and 3 × 105 cells / mL. The results showed that the survival rate of larvae was 48.33 ± 7.76 %, 71.6 ± 6.50 %, 58.67 ± 3.21 %, respectively. Among three groups, 1.5 × 105 cells / mL group had the highest survival rate, which was significantly higher than the other two groups (p < 0.05).
In experiment III, larvae were cultured at the optimal microalgae concentration obtained from experiment II (1.5 × 105 cells / mL). Three different stocking densities of larvae in 200 pcs / L, 400 pcs / L, 800 pcs / L were tested. The results showed that the survival rate of postlarvae was 59.35 ± 4.01 %, 56.96 ± 2.38 % and 52.63 ± 2.51 %, respectively. No significant difference was shown in comparing 200 pcs / L to 400 pcs / L (p > 0.05) and 400 pcs / L to 800 pcs / L (p > 0.05), but there was a significant difference between 200 pcs / L and 800 pcs / L (p < 0.05); The productivities of postlarvae were 118.70 ± 8.02 pcs / L, 227.83 ± 9.51 pcs / L, 421.03 ± 20.09 pcs / L and there were significant differences in each group (p < 0.05).
In experiment IV, postlarvae (0, 3, 6, and 9 days after settling) were acclimated to freshwater within 0, 3, 6, 12, 24 and 48 hours, respectively. The survivorship showed that the group of 0 day settled postlarvae were not suitable for freshwater acclimation while deaths were occurred at each time point. 100 % survival rates were shown in the groups of 3 and 6 day settled postlarvae while the acclimation time is extended to 12 hours. The 100 % survival rate was also achieved in the group of 9 day settled postlarvae while the acclimation time is extended to 3 hours.
In experiment V, the postlarvae after acclimation were reared for 14 weeks at three different stocking densities including 1 pcs / L, 2 pcs / L and 3 pcs / L. No significant difference was found among three density groups (p > 0.05) with the well survival rates of 91.33 ± 4.16%, 89.66 ± 4.04%, and 94.44 ± 6.50%, respectively. In addition, the body growth of each group approached stationary after 10 weeks. At 10 week, the daily growth rates of body length for each group were 0.23 ± 0.02 mm, 0.18 ± 0.03 mm and 0.17 ± 0.03 mm, respectively. Among them, the 1 pcs / L group was significantly higher than the other two groups (p < 0.05).
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