36 JUNE 2022 • WORLD AQUACULTURE • WWW.WA S .ORG a results during the first month of the study. Two feed placement methods based on grazing behavior were implemented. In one placement (P1), feed was placed in the tray center and conch were placed with their siphonal canal positioned towards the gel diet and each other (Fig. 10a). In the other placement (P2), feed was placed in tray corners and conch were positioned with their siphonal canals toward the feed (Fig. 10b). In addition to the gel feed, conch diets were supplemented weekly with 3-6 detrital blades of seagrass Thalassia testudinum per tray. Seagrass blades, covered with epiphytes, were collected from seagrass meadows near the Naguabo Fishing Association. Conch also fed on natural periphytic algal growth that became established on tray walls. During the first four weeks of the study, maintenance of sand trays with conch was performed on a three-day cycle. One at a time, each tray was removed with the conch from their respective position in the tanks and placed in a spraying station. A spray bar with pressurized seawater was used to push uneaten feed and feces Tanks were labeled A and B and trays in the tank were assigned a number (A1 to A4 and B1 to B4). Each tray was stocked with three milk conch; four trays had two males and one female (Tank A) and four trays had one male and two females (Tank B). To distinguish between sexes, pink nail polish was used to mark females (Fig. 8). If there were more than one female in a tray, ‘X’ and ‘I’ symbols were used to differentiate them. To discern between the two males, size differences and shell characteristics were used. Conch were fed daily with a gel diet consisting of dry Ulva lactuca seaweed (12 percent), shrimp pellets (24 percent) and gelatin (4 percent) (Fig. 9a). Solid components were combined in distilled water (60 percent) and heated until boiling. The resulting green paste was poured into aluminum trays and allowed to harden in a refrigerator (Fig. 9b). After hardening, the gel diet was cut into cubes and stored in a freezer. For feeding, gel diet cubes were weighed daily (Fig. 9c) throughout the 10-wk study period. The amount of feed remaining in each tray 24 h after feeding was determined. Minimum and maximum amounts were established (1-6 g) using feed uptake TABLE 1. Water quality of integrated nursery system prior and during M. costatus husbandry (12/07/21 – 2/16/22). Results are expressed as mean ± standard deviation (n=number of observations) and range for dissolved oxygen. Var iable Ideal Acceptable Range Resul ts pH 8.1 7.6 - 8.1 7.8 ± 0.1 (n=10) Salinity (ppt) 36 28 - 40 39.0 ± 1.5 (n=68) Temperature AM (C) 28 24 - 30 24.3 ± 0.6 (n=66) Temperature PM (C) 28 24 - 30 24.7 ± 1.0 (n=68) Dissolved oxygen 85 80 - 90 80.9 - 86.8 (n=2) (% saturation) FIGURE 7, LEFT and MIDDLE. Milk conch M. costatus reproductive organs: female egg groove (a) and male verge (b) (Photo: FAU Harbor Branch ). FIGURE 8, RIGHT. Chalier Dones-Ortiz, research intern, marking female conch. Females were marked using pink nail polish with an ‘I’ or a ‘X’ to distinguish between females when more than one was in the same tray. Males were not marked (Photo: Victoria Cassar). b
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