38 JUNE 2022 • WORLD AQUACULTURE • WWW.WA S .ORG Results and Discussion During the 10-wk study, water quality, system operation and conch observations were recorded. Apart from salinity, all other water quality parameters remained in acceptable ranges (Table 1). Minimal differences were seen between morning and afternoon mean temperatures and these did not vary greatly (Fig. 12). The acceptable temperature range for growing queen conch is 24-30 C. As the study took place during the winter, temperature in the system was on the lower end of the range. Mean minimum air temperature in coastal areas of Puerto Rico from January to February is 24 C (Gómez 2014). The stability of water temperature in the nursery system could have been due to limited exposure to direct sunlight and the interaction with outside air due to exposure of the open trays with spray bars. Salinity slowly increased over time, starting at 36 ppt at the trial beginning and reaching a maximum of 41 ppt after six weeks (Fig. 13). The outdoor location of the nursery system, with open tanks FIGURE 11. (a) A pressurized spray bar was used to remove feces and any excess feed from the sand substrate in the tray, (b) a siphon was used to remove debris from the bottom of the tank underneath the trays, (c) and debris from tank siphoning was settled and the supernatant was returned to the system (Photos: a, b – Victoria Cassar; c – Megan Davis). conch and the system. By the second month, the frequency of the spraying and siphoning cycle was decreased from every three days to once a week. General systemmaintenance included weekly pump filter cleaning, topping off sump seawater level as needed and a partial water exchange halfway through the study. Daily observations were made regarding remaining feed, feces in the tray and conch buried in sand. Animal acclimation or welfare monitoring such as active grazing and movement, mucus production that can be a sign of stress, mating and egg laying were recorded. Additionally, water quality parameters were monitored throughout the study. Temperature was measured twice daily (0800 and 1300 h) with an infrared thermometer. Salinity was measured daily with a refractometer. In addition, pHwas measured with a pH meter pen and dissolved oxygen concentration was measured with a YSI meter weekly. FIGURE 10. (a) Gel-diet placed in center of tray with conch facing each other (P1) and (b) conch placed in center facing towards the food in tray corners (P2) (Photos: Chalier Dones-Ortiz). a b a b c
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