World Aquaculture December 2019

32 DECEMBER 2019 • WORLD AQUACULTURE • WWW.WA S.ORG ratios of males to females (1:1 and 1:2) and and fed different gel diets (koi chow and catfish chow) in a recirculating system and found no differences in egg mass production and in veliger development between treatments (Gillette 2003). HBOI has been operating a land-based Integrated Multi-Trophic Aquaculture (IMTA) system since 2012. In this system, culture of fed organisms (finfish and shrimp) is combined with culture of organisms that extract dissolved inorganic nutrients (seaweeds) or particulate organic matter (urchins, sea cucumbers, shellfish) and, hence, the biological and chemical processes at work are in balance (Wills et al. 2012, Laramore et al. 2018). There have been no studies that have examined Florida fighting conch as an extractive species in an IMTA system. Therefore, HBOI’s IMTA systemwas used for a four-week (20 June – 17 July 2019) fighting conch captive breeding study to determine the effects of sex ratio on reproductive output and to observe behavior of the species in this system. Florida Fighting Conch Captive Breeding Study Methods One hundred adult fighting conch were collected from the Florida Keys by Florida Keys Marine Life LLC and shipped overnight to HBOI. Upon arrival mean seawater temperatures in the shipping bags and the IMTA tanks were 25 C and 28 C, respectively. Thus, conch did not require acclimation with this minimal temperature difference. As a quarantine measure, conch were dipped in fresh water for five seconds prior to stocking in tanks. Conch were sexed and their shell lengths (SL) determined with calipers to the nearest millimeter. Sex was determined by holding conch with their aperture facing down and reproductive organs were observed when they emerged partially from their shell. The male has a verge and the female has an egg groove (Fig. 4). For identification purposes, each conch was numbered with fluorescent nail polish, blue for males and pink for females (Fig. 5). Conch were transferred to two fiberglass study tanks (0.64 m wide × 3.1 m long). Each tank was divided into five equal sections using 0.32-m 2 polypropylene baskets with a mesh of 6 mm and window screen secured on the bottom (Fig. 6). They were elevated from the tank bottom using ½-in PVC pipes. A 1-2 cm deep layer of coarse aragonite crushed coral sand substrate (1-3 mm diameter, Carib Sea) was placed on top of the window screen of the baskets. The sand provided substrate for the broodstock to lay egg masses and also served as additional biofilter for the system. Water depth above the substrate was 15-17 cm. Study tanks received recirculated seawater from a centralized filtration system that delivered water to various components of the IMTA system (Laramore et al. 2018). Seawater entered each basket through a small hose (6-mm diameter) and aeration was provided with one air diffuser per basket. The water turnover rate for each tank was 12 times per day at a flow rate of 0.6 L/min per basket. Water drained through a 2-in diameter standpipe at the end of each tank and then recirculated to the IMTA system. The tank bottom and sand were FIGURE 4. Adult Florida fighting conch reproductive organs: (left) male with black verge, and (right) female with egg groove running the length of the foot. Photos: Megan Davis. FIGURE 5. Adult Florida fighting conch numbered for the study with colored nail polish, blue for males and pink for females. Photo: Megan Davis. FIGURE 6. Two study tanks with five baskets per tank. Photo: Megan Davis.