World Aquaculture December 2019

42 DECEMBER 2019 • WORLD AQUACULTURE • WWW.WA S.ORG consultation with an interagency planning group representing local, commonwealth and federal government agencies. The research permit facilitated the construction of the grow-out site supporting these studies. The site was located outside Rincon Lagoon on the eastern shore of Boquerón Bay. The site was selected based on water quality, accessibility, and land-use practices in the area. A shoreline survey was conducted and there were no conflicting residential structures or point- source discharges. Water quality at the site reflected conditions suitable to support oyster survival and growth (Mattox 1949, Lemos et al. 1994). In addition, the shallow depth did not interfere with local tourist or boating activity and facilitated easy lease management from a small workboat. Twenty-four baskets filled with recycled shell were placed in the mangroves in Rincon Lagoon for larval recruitment in July 2012, targeting the August through November rainy season. Eight-inch PVC pipe structures were used to suspend oyster baskets at the grow-out sites (Figs. 8 and 9). Each of three structures suspended up to four baskets. The floating systems were anchored using sand screws. Floats were oriented so that baskets were parallel to the coast and wave action. Twelve oyster baskets fromRincon Lagoon were transferred to the farm site in January 2013 and twelve baskets were left in Rincon Lagoon for comparison. Army Corps of Engineer (ACOE) permits accommodated only six months of data collection, baskets were returned to Rincon Lagoon in June 2013. Ten shells were selected from each basket and the length and width of all recruits were measured using metric calipers. Five shells from each basket at each site were collected to determine condition index. Five oysters were also collected from the natural population growing on mangrove prop roots for comparison. The physiological condition of oysters is described by its condition index (CI) and length to wet oyster weight ratio (L:W). The condition index of all oysters collected was determined using the internal shell cavity capacity (ISCC) as described by Kreeger (1993): TABLE 3. Oyster physiological parameters compared among baskets in Rincon Lagoon and Farm Site and directly from the prop roots of red mangroves. Location Length:Wet Weight Condition Index Rincon Lagoon 2.80 ± 0.66 1255 ± 616 Farm Site 3.66 ± 0.86 1379 ± 858 Mangroves 2.10 ± 0.39 958 ± 780 TABLE 4. Average seagrass percent cover, shoot length and shoot density before and after float deployment at the Farm. Shoot length decreased and shoot density increased over the six month period that the floats were deployed. Cover Shoot length Shoot density Growth rate (%) (cm) (#/m 2 ) (cm/day) Before deployment 82 ± 8 9.8 ± 0.4 101 ± 19 0.32 ± 0.04 After deployment 67 ± 6 8.7 ± 0.3 155 ± 12 0.29 ± 0.03 FIGURE 8. Baskets were moved from the lagoon to the farm site and placed in PVC float structures. FIGURE 9. Detail of farm float design. Materials used to construct this structure are readily available and inexpensive. Recycled oyster shell in the baskets form the substrate for spat recruitment.