World Aquaculture December 2018

WWW.WA S.ORG • WORLD AQUACULTURE • DECEMBER 2018 45 ( C O N T I N U E D O N P A G E 4 6 ) number of PLs stocked, total feed input, number of shrimp harvested and weight of shrimp harvested (Figs. 7 and 8). Observations on mortalities and other pertinent information were recorded throughout the production season. Basic production information from cooperating farms, water chemistry, pond Vibrio and shrimp health were statistically analyzed and differences compared between control and probiotic-treated ponds. Main Results Survival and yield of shrimp were low in all study ponds regardless of probiotic application (Table 2). Although there was a trend towards greater survival and yield in probiotic treatments at GPA and GAS, differences were not significant (p > 0.05). One pond in each of the probiotic and control groups at FS had complete mortality very early in the season and were eliminated from the study, resulting in fewer ponds for comparison at this farm. Water Quality and Algal Community Effects Selected water quality variables are summarized in Table 1. Mean temperatures across farms were between 29 and 30 C, which is slightly lower than reported in previous years. There were no temperature differences between treated and control ponds. Salinity was typically low on all farms, averaging 2.3-3.0 ppt at GPA, 4.5 ppt at FS and 3.9 ppt at GAS. Total ammonia-nitrogen and nitrite-nitrogen were within acceptable ranges with no significant differences between probiotic-treated and control ponds on any farm. Mean pH was similar for Alabama farms and there were no differences between treated and control ponds. However, several ponds at GPA, both treated and control ponds, had exceptionally high pH (>10) during the first three weeks after stocking, when water was unusually clear and aquatic weeds (southern naiad and Chara sp.) were growing in profusion. High shrimp mortality occurred at this time, although the exact level was unknown. Some of the ponds were subsequently restocked with 25-50 percent of the original stocking density. One pond originally assigned to the probiotic treatment was eliminated from the study and replaced with another pond due to high mortality. Anabaena , Microcystis , Oscillatoria , Euglena and Prymnesium were detected in pond water samples on the two Alabama farms, with Oscillatoria and Prymnesium being the most prevalent. Algae were not identified and enumerated at the Florida farm. Microscopic examination of water samples revealed Prymnesium was present at both Alabama farms throughout most of the production season, with higher density (mean range: 79-118 million cells/L) observed at FS than GPA (range: 40-47 million cells/L). Prymnesium can release phytotoxins that have been associated with fish kills in low-salinity rivers and reservoirs FIGURE 9. In vitro assay examining the inhibitory capacity (as shown by zone of clearing adjacent to wells) of Sanolife® Pro-W on select Vibrio species following overnight growth. A) Vibrio parahaemolyticus cultured on TSB with 2% salt and B) Vibrio alginolyticus on blood agar. Wells were loaded with either: 1) cell-free culture supernatants of Sanolife® Pro-W or 2) whole culture of Pro-W. TABLE 2. Average survival (%) and yield (kg/ha) of shrimp cultured in probiotic-treated ponds and control ponds on three commercial shrimp farms in Alabama and Florida, including Greene Prairie Aquafarm (GPA), Forkland Springs (FS) and Gulf American Shrimp (GAS). Farm Survival (%) Yield (kg/ha) GPA – Probiotic 29 ± 16 2442 ± 751 GPA – Control 14 ± 13 1368 ± 923 FS – Probiotic 26 ± 25 1498 ± 880 FS – Control 23 ± 3 2312 ± 1145 GAS – Probiotic 21 ± 10 2513 ± 1131 GAS – Control 12 ± 9 1666 ± 1350 A B