28 SEPTEMBER 2017 • WORLD AQUACULTURE • WWW.WAS.ORG Egg Incubation, Larval and Juvenile Rearing After hormone treatment, eggs were released naturally and collected in 200-L tanks with 0.3-mm mesh screens under the outflow of the spawning tanks. Eggs were removed from collectors 12-14 h after spawning at the embryo somatogenesis stage (Fig. 5A). The number of floating and sinking eggs was estimated volumetrically (Ibarra-Castro and Alvarez-Lajonchère 2011b). Incubation and larval rearing were conducted in one 7-m3 cylindrical fiberglass tank with black walls and a white bottom. Initial stocking density was 82 floating eggs/L. Hatching rates and survival at hatching and first-feeding stage were determined following Martinez-Brown et al. (in review). Seawater used in the larval rearing trial was treated in a multicartridge (1 μm relative retention) filter, a continuous UV-lamp (30,000 µWs/cm) and a 0.2-µm ultrafilter (FreshPoint™ U440 Pentek). Water quality parameters during egg incubation and larval rearing were temperature 26 ± 0.4 C, salinity 35 g/L, dissolved oxygen 7.0 ± 0.6 mg/L (105 ± 9 percent saturation), pH 7.9 ± 0.1 and total ammonia-nitrogen of less than 0.5 mg/L. A water quality and environmental management protocol was established for egg incubation, larval rearing, addition of microalgae and weaning following Gutiérrez-Sigeros et al. (in review) and Ibarra-Castro et al. (in preparation). A daily work plan FIGURE 9. Size grading of Pacific white snook fry. A B C FIGURE 10. Pacific white snook fingerlings during the weaning process: A) snook larvae at the Artemia step (TL 5.5 mm), B) co-feeding step (TL 18.3 mm) and only pelleted feed step (TL 26.6 mm). FIGURE 11. Final size grading of Pacific white snook. A B FIGURE 12. A) Fingerlings for delivery to producers and B) a harvested Pacific white snook fingerling.
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