40 SEPTEMBER 2016 • WORLD AQUACULTURE • WWW.WAS.ORG Larval Rearing and Nursing Of the hatched larvae, 2.175 million healthy larvae averaging 2.11 mm (2.03-2.15 mm) total body length were stocked in five 40-t circular concrete larval rearing tanks (LRTs) at 11 larvae/L. All LRTs were indoors with clear acrylic transparent sheets on the roof above the tanks. Each tank was provided with an aeration grid with air diffusers. The central standpipe was fixed in such a way that a diffuser placed inside the pipe created an upwelling current that provided gentle ripples on the water surface. The green algae Nannochloropsis sp. was added to LRTs from 1 to 25 days post-hatch (dph) at a daily rate of 200 to 400 L/tank to maintain 1-3 x 104 cells/mL. After 50-52 hours from hatching, screened rotifers Brachionus rotundiformis (68-146 μm) were added twice daily at 0700 and 1600 h. A density of 2-3 rotifers/mL was maintained in the LRTs during 2 to 5 dph and 7-10 rotifers/ mL between 6 to 25 dph. Prior to their introduction into LRTs, rotifers were cultured in yeast and Ori-One (Skretting, France; 56 percent protein, 17 percent lipids, 37 mg/g HUFA and >5 DHA/ EPA), followed by 12 h of enrichment with Red Algamac1 (2.59 percent EPA, 38.94 percent DHA) at 0.09 g/million rotifers. Rotifers were harvested using a specially designed harvest box with 60-µm mesh screens, which facilitated concentrating, rinsing and cleaning of rotifers before being fed to grouper larvae (Fig. 1). From 2-5 dph, copepod nauplii collected from shrimp ponds were fed to larvae at 0.03-0.06 individuals/mL and from 7-14 dph adult copepods were introduced at 0.2-0.5 individuals/mL. Newly hatched Artemia nauplii were provided from 11-17 dph and red Algamac-enriched Artemia from 14-35 dph. Harvested Artemia nauplii were stored at 4 to 6 C to maintain size and quality and fed in four rations per day. The feeding of formulated feeds started on 11 dph with Love Larva No. 13 (< 200 μm; 57.40 percent crude protein, 12.42 percent lipid) until day 20 dph. From 18-30 dph artificial Love Larva No. 2 (200-310 μm) and from 25-35 dph Love Larva No. 3 (310-480 μm) were provided. Water was not renewed from 0-7 dph and water exchange started around 8-10 dph at 25 percent at night to maintain water quality and rotifer density, followed by 50 percent on 11-12 dph and 100 percent on 13-20 dph. Water exchange increased to 150 percent on 21 dph followed by 200 percent on 30 dph (Fig. 2). Photoperiod was maintained at 14 hours of light and 10 hours of dark during the rotifer feeding stage using florescent light (400-600 lux). After 30 dph, natural photoperiod was maintained. Water quality during the larval rearing stage was: water temperature 26.0 ± 0.8 C, dissolved oxygen concentration 5.2 ± 0.8 FIGURE 1. Tank for harvesting rotifers (Brachionus rotundiformis). FIGURE 2. Feeding and water exchange scheme for rearing orange-spotted grouper larvae. FIGURE 3. Harvesting orange-spotted grouper fingerlings.
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