40 JUNE 2022 • WORLD AQUACULTURE • WWW.WA S .ORG (n = 11), while females were larger, with a mean shell length of 10.5 cm (n = 11). At the beginning of the study, to determine if conch were consuming the gel diet, observations of grazing and feces confirmed this activity. Feed amounts varied throughout the study until specific quantities per tray were determined. Feeding rates ranged from 1-6 g/tray and were increased or decreased according to the quantities of feed remaining after 24 h. Low amounts of remaining feed and the presence of feces were considered signs of animal normalcy and well-being. Feed remaining in the morning was estimated daily as the percent remaining. By week 10, the amounts of feed remaining in the four A trays as well as tank B trays decreased and reached 0 percent and 0-5 percent, respectively (Table 2). Thus, established feeding amounts became more refined as the study progressed. Food placement methods were done arbitrarily at first but later were modified by subjectively assessing tray feeding behaviors using methods P1 or P2 (Fig. 10a, b). As the trial developed, only tray B1 conch received feed placement method 1 (P1) based on their grazing behavior and feed consumption. All other trays of conch were given placement method 2 (P2). Establishing a specific position for the conch meant that the next day we had an idea of howmuch they had moved, which was an indicator of normal behavior. The majority of conch activity occurs at night and conch tend to bury during the day if fed to satiation (Davis 2005). In this study, milk conch were active during the day, although they were also observed being still, partially buried or substantially buried. This was interpreted as a sign of normalcy and was not considered a sign of conch malnutrition due to underfeeding. For the whole study, the percentage of buried conch ranged from 0-100 percent for all trays (Table 2). Contrary to work done by Shawl and Davis (2004), no mating or egg laying events occurred during the 10-wk study. Mean temperatures rangef from 22-25 C, where egg mass laying was found to slow or stop (Shawl and Davis 2004). Sub-optimal temperatures may have played a role in deterring an adequate environment for conch reproduction. Conch density may have also affected spawning activity. The stocking density was 3 milk conch/0.18-m2 tray, which was far denser than what was used by Shawl and Davis (2004) (1.2 milk conch /10 m2), where mating and egg laying were recorded. Conclusion This study was successful in establishing an understanding of how to operate a conch nursery recirculating aquaculture system and the protocols needed for the effective husbandry of hatchery-reared queen conch juveniles. Ten weeks was sufficient to test the nursery system as it allowed stabilization of water quality, modification of system design (e.g., pump selection, tray spray bars and flow rate) and establishment of biological filtration in sand trays. Adult milk conch were a good proxy mollusk to determine conch rearing techniques that are transferable to culturing juvenile queen conch with assurance of their well-being. At the study end, we stocked the first batches of cultured queen conch juveniles into the system (2/16/22) (Fig. FIGURE 14. (a) Puerto Rico hatchery-raised juvenile queen conch (20-40 mm) and (b) on the sand in a nursery system tray (Photos: Megan Davis).
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