World Aquaculture December 2019

WWW.WA S.ORG • WORLD AQUACULTURE • DECEMBER 2019 33 siphoned once per week to remove feces and settled bioflocs from the IMTA system. Of the 100 conch delivered to HBOI, only 18 were males. Therefore, 60 fighting conch (18 males and 42 females) were stocked at two sex ratio treatments: 1 male with 5 females (1:5; n=6 replicates) and 3 males with 3 females (3:3; n= 4 replicates). These replicates were randomized among ten baskets in two tanks. The density was six conch per basket, equivalent to 18.5 conch per m 2 . Conch were fed to satiation (approximately 1.5 g per individual) once per day with a benthic gel diet that consisted of 31 percent blended koi chow, 43 percent dry flakes of Ulva lactuca that was collected fresh from the IMTA system, 4 percent pork skin gelatin, and 5 percent hot fresh water (Gillette 2003, Shawl and Davis 2004, C. Robinson pers. comm.). The mixture was spread out on aluminum trays to set overnight in a refrigerator (4 C), after which it was cut into pieces and stored in a freezer (-20 C) (Fig. 7). In addition to the prepared diet, conch fed on settled bioflocs that naturally entered tanks from the IMTA system (Fig. 8). Observations were made daily and egg mass laying and matings were recorded. Amating was considered each time a male was positioned behind and partially on top of a female, or with the male’s propodium touching the shell lip of the female (Fig. 9). Egg masses were removed by hand, placed into small containers with seawater and characterized (Fig. 10). Volume displacement of each egg mass was measured with a 100-mL graduated cylinder filled with 50 mL of seawater. For each egg mass the number of eggs per millimeter of strand was counted (n = 5) using a stereomicroscope (40 × ) equipped with a eye-piece micrometer. To estimate the number of eggs per egg mass, a correlation between egg mass volume and number of eggs was determined using three small subsamples from ten egg masses (n=31). These subsamples were equivalent to approximately 1 mL of displacement in a 10 mL graduated cylinder that was filled with 5 mL of seawater. The exact displacement volume of each subsample ranged from 0.8 to 1.1 mL (Fig. 11). Each subsample of egg strand was uncoiled and their length (mm) measured with a ruler (Fig. 12). The mean length of the egg strand (n=25) was multiplied by the mean number of eggs per millimeter of egg strand (n=50) to calculate the mean number of eggs per equivalent 1 mL subsample. The strength of correlation was tested with one-way ANOVAwith a post-hoc Tukey HSD test (p <0.05). Water quality parameters were measured on the IMTA seawater that entered the study tanks. Temperature, salinity, and pH values were determined daily. Total ammonia nitrogen (TAN), nitrite, and alkalinity were measured three times per week. Tanks were located within a metal greenhouse with continuous illumination (32W). Starting on July 9, tanks were covered from 5:00 PM to 8:00 AM to provide the conch a period of darkness. All statistical tests were run in the R studio software (RStudio Team 2015). ( C O N T I N U E D O N P A G E 3 4 ) FIGURE 7. Gel diet for adult Florida fighting conch. Photo: Megan Davis. FIGURE 8. Florida fighting conch actively grazed on settled biofloc from the IMTA. Photo: Megan Davis. FIGURE 9. Florida fighting conch mating positions for copulation and internal fertilization: (left) male 25 behind female 29 and (right) male 25 with shell and propodium on female 29. Photos: Megan Davis.