50 SEPTEMBER 2012 estimated based on number of eggs and nauplii produced per spawn. Shrimp reproductive performance indexes, the numbers of females reaching stage IV and the amount of eggs per spawn, fertilization rate and hatching rate from the fish roe and control dietary treatments were submitted to Student’s t-test for one way classification analysis of variance using dietary treatment as the dependent variable. In phase 1, comparison was made between the tuna roe diet and a control diet (control A) consisting of 50 percent commercial maturation diet and 50 percent squid, under natural mating conditions. The reproductive performance of shrimp fed the semi-moist tuna roe diet was consistently inferior to shrimp fed the control diet (Table 4). In phase 2 and 3 experiments, the semi-moist diet was compared with the commercial diet alone (control B). In the phase 2 study, the comparison was made under natural mating conditions; in phase 3, the comparison was made using artificial insemination. Results of the phase 2 study (Table 5) showed that similar effects were achieved on most reproductive traits as in phase 1 except significantly fewer females reached ovarian maturity level of stage IV. Consequently, there were fewer female spawners in the tuna roe dietary group. It is possible that this may be the result of reduced sperm quality of male broodstock from the fish roe dietary group. In the phase 3 study, only female broodstock were used after unilateral eyestalk ablation was performed to boost female performance. When female brooders reached stage IV, the best spermatophores available from males that were fed under regime A were used to artificially inseminate females. The semi-moist diet produced a similar number of eggs per spawning, fertilization rate and hatching rate in shrimp brooders as regime B (Table 6), though the maturity of female to stage IV was delayed. The declining egg number per spawning from the same control diet from phase 2 to phase 3 comparison implied an age effect on female reproduction. Discussion Shrimp maturation is the process of conditioning broodstock to stimulate gonad development and induce mating, spawning and hatching of eggs to produce viable larvae (Juarez et al. 2003). To obtain optimal larval survival, time must be allowed for maternal yolk investment (Quackenbush 2001). The biochemical composition of the ovary reflects the typical nutrient accumulation associated with maturation (Palacios et al. 2000). The results of this research reflect the contribution of diet because feeding regime was the only variable. After egg release, developing shrimp larvae are entirely dependent on yolk reserves for nutrition because they do not hatch with functional mouthparts. Shrimp larvae require up to four post-hatch molts before they are capable of independent prey capture and feeding. Egg yolk is the main nutrient reserve used before penaeid shrimp reach nauplii stage V. In general, adequate nutrition is not only necessary for gonadal maturation (Palacios et al. 2000), but also is critical in embryonic and initial larval developments sustained by the yolk reserve (Wouters et al. 2001). TABLE 3. Composition (%) and cost analysis of the tuna roe based semi-moist diet. Ingredient Price ($/kg) Composition (%) Cost ($/kg) Tuna roe 5.51 55 3.03 Soybean meal 6.06 12 0.73 Glutinous rice flour 4.41 5 0.22 Spirulina 56.57 5 2.83 Black algae powder 57.65 2 1.15 Mineral mix 25.53 1 0.26 Vitamin mix 130.00 1 1.30 Lecithin 50.00 3 1.50 Distilled water 0.07 15 0.01 Soybean oil 5.00 1 0.05 Total 100 11.07 TABLE 2. Fatty acid levels (% of total fatty acid fraction) of the six tuna roe samples compared with the published blood worm fatty acid profile. Fatty acid Blood Tuna roe worm (Mean ± Std.dev) Myristate (14:00) 0.89 2.11 ± 0.23 Palmitate (16:00) 7.5 22.6 ± 1.1 Palmitoleate (16:1n7) 3.58 3.62 ± 0.34 Stearate (18:00) 6.51 5.53 ± 0.23 Oleate (18:1n9) 7.09 14.03 ±1.98 Linoleate (18:2n6) 1.03 1.00 ± 0.11 Linolenate (18:3n3) 0.28 0.33 ± 0.06 Octadecatetraenoate (18:4n3) ??? 0.39 ± 0.14 Eicosenoate (20:1n11) 14.9 1.02 ± 0.25 Arachidonate (20:4n6) 4.1 5.0 ± 1.1 EPA (20:5n3) 29.3 6.2 ±0.8 Erucate (22:1n13) 0.41 0.39 ± 0.08 DHA (22:6n3) 12.9 38.1 ± 2.5 EPA/DHA ratio 2.27 0.16 In shrimp maturation, shrimp are often fed with freshfrozen items at 20-30 percent of body weight per day, often representing the greatest expense in shrimp maturation. It is often cost-prohibitive to rely on only certified products in commercial hatcheries. For shrimp operations on Guam and other islands of the western Pacific region, the issue is even worse. Obtaining consistent and steady supplies of conventional fresh-frozen maturation food items for hatchery operations is a challenge, because of the high cost and the time required for shipping and importation. The estimated cost for obtaining certified SPF bloodworms delivered to Guam is over $90/kg, too expensive for shrimp growers on Guam. Semi-moist diet of fish roe costs about 11 percent of that (Table 3).
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