World Aquaculture December 2020

40 DECEMBER 2020 • WORLD AQUACULTURE • WWW.WA S.ORG Observations, Outcomes and Recommendations Before we received them from fishermen, the conch had experienced a long journey from the fishing grounds tied together in groups of five. Due to this handling stress, we were unsure about the duration of acclimation to the habitat inside the enclosure. Almost immediately after placement in the enclosure, conch were seen grazing, which was a good sign that they had acclimated quickly. By tracking conch movements over three months, we observed that conch often preferred to occupy seagrass areas of the enclosure rather than coarse sandy areas. Although conch seemingly move slowly, the maximum distance conch traveled between observation days (24-48 h) was 40 m, nearly the diameter of the enclosure (42 m). At the end of the study, 98 percent of the conch had survived. Only one conch was lost from predation by an octopus (Fig. 10) and another four died shortly after introduction to the enclosure. Study site flora was comprised of seagrasses (turtle grass Thalassia testudinum , manatee grass Syrngodium filliforme , shoal grass Halodule beaudette ) and macroalgae ( Batophera oerstedii , Halimeda spp., Rhipocephalus phoenix , Udotea cyathiformis , and Laurencia spp.). Turtle grass was the most common plant species in the enclosure. Conch actively grazed on epiphytes of seagrass blades in the enclosure but this feeding activity did not affect seagrass shoot density over the 12-wk study. However, based on visual observations of epiphyte loads on turtle grass inside and outside the enclosure at the end of the study, conch had a positive impact on keeping blades of seagrass clean (Fig. 11). Grazing may increase photosynthesis and thereby increase seagrass biomass over time. Faunal diversity at the study site gradually increased after conch were placed in the enclosure. Fish species such as Nassau groupers, sergeant majors, and parrotfish were attracted to the enclosure itself. Others such as southern stingrays seemed to be interested in the conch and a few (e.g. barracuda) seemed to be interested in the research divers. Because no baseline for the fauna community previously existed for this site, it is unclear if the fauna observed reflected a permanent increase or merely a temporary attraction to the enclosure. However, there was an increase in the number of FIGURE 7. Queen conch purchased from local fishermen (Photo: Laura Issac Norton). FIGURE 9. Examples of conch from the study: the youngest conch with the thinnest lip (a), the oldest conch with the thickest lip (b), the conch with the shortest shell length (c), and the conch with the longest shell length (d) (Photos: Megan Davis). FIGURE 8. Measurement of shell length of a queen conch with a livestock tag attached to the spire of the shell (Photo: Megan Davis). FIGURE 10. An octopus preying upon one of the study conch (Photo: Laura Issac Norton).