Two 8-week feeding trials were conducted with juvenile Pacific white shrimp, Litopenaeus vannamei (Boone) to compare the growth and performance of animals fed a series of experimental and commercial pelleted shrimp and fish feeds and dietary feeding regimes within an indoor running-water culture system and an outdoor zero-water-exchange culture system. The best overall shrimp growth performance was observed for animals fed the experimental shrimp diet and all-day feeding regime under outdoor zero-water-exchange culture conditions. Final body weight and average weekly growth rate under these conditions were 2.8 and 3.4 times greater, respectively, than animals of similar size fed with the same diet under indoor running-water culture conditions. Although direct comparison between indoor and outdoor culture systems is difficult because of the lower indoor water temperatures, and consequently lower mean daily feed intake of animals, it is believed that the higher growth and feed performance of animals reared under outdoor 'green-water' culture conditions was primarily due to their ability to obtain additional nutrients from food organisms endogenously produced within the zero-waterexchange culture system. The most promising features of zerowater-exchange culture systems are that they offer increased biosecurity, reduced feed costs and water use for the farmer, and by doing so provide a potential avenue of moving the shrimp culture industry along a path of greater sustainability and environmental compatibility. KEY WORDS

The aim of this study was to assess the impact of a commercial probiotic, Sanolife PRO‐F, on water quality, growth performance, blood profiles and intestinal morphometry of monosex Nile tilapia. A field trial was conducted for 10 weeks in which tilapia fingerlings (20 ± 1.26 g) were randomly distributed into three replicate ponds which were subdivided into three treatment groups, receiving Sanolife PRO‐F at 0 (B0), 0.1 (B1) and 0.2 (B2) g/kg diet, respectively. The results showed a significant improvement in growth performance, feed conversion ratio and blood profiles in tilapia fed on treated diets. The whole intestinal lengths, anterior and terminal intestinal villi heights and anterior goblet cells count were greater in tilapia fed on treated diets. There were no noticeable differences in growth and intestinal morphology between tilapia fed on B1 and B2 diets. The ammonia concentration in water was lower with B1 diet while electric conductivity, salinity and total dissolved solids were higher with the B2 diet. The pH level of pond water was enhanced by both diets, B1 and B2. In conclusion, application of Sanolife PRO‐F at 0.1–0.2 g/kg diet might have beneficial effects on growth, immunity, stress responses and gut health and function as well as the water quality of farmed Nile tilapia.

Disease problems have emerged as major constraints in aquaculture production. The prophylactic application of antibiotics is expensive and detrimental, i.e. selection of bacteria that are drug-resistant or more virulent and the prevalence of drug residues in reared animals. Probiotics, which compete with bacterial pathogens for nutrients and/or inhibit the growth of pathogens, could be a valid alternative to the prophylactic application of chemicals. A mixture of speci¢c Bacillus strains was designed following a research programme on the ability of numerous Bacillus strains to inhibit a range of pathogenicVibrio strains, to grow under conditions prevailing in shrimp hatcheries and to degrade waste products. These strains were then included in bioassays and challenge tests in order to con¢rm the lack of toxin production and pathogenicity to humans, target organisms and the environment. Here, we report on the performance of a commercially available mixture of Bacillus strains (SANOLIFE s MIC), using data from Asian and Latin-American hatcheries, with Penaeus monodon (Fabricius 1798) and Litopenaeus vannamei (Boone 1931). These results show that probiotics may be a suitable alternative to the prophylactic use of antibiotics. Obviously, minimizing the risk of vibriosis demands a multi-disciplinary approach, including good hygiene and sanitation measures to reduce the input of potential pathogens, as well as a suitable farm management.

Despite the shrimp ability to obtain additional nutrients from food organisms endogenously produced within the Ôgreen waterÕ system has been suggested as one of the causes for the better performance of Pacific white shrimp reared in Ôgreen waterÕ in comparison with Ôclear waterÕ, the nutritional components responsible for these effects have yet to be determined. The present study aims to understand the importance of natural food organisms in zero-water exchange systems as source of essential fatty acids for the Pacific white shrimp Litopenaeus vannamei. Five treatments were tested: two conducted in mesocosms systems with shrimp-fed diets containing either fish oil (FO) or olive oil, and another three conducted in clear water with shrimp-fed diets containing either olive oil, a docosahexaenoic acid (DHA)-rich oil or an arachidonic acid (ARA)-rich oil. The presence of higher levels of fatty acids 16:1n-7, 17:1, 20:4n-6, 20:3n-3 and 22:5n-6, characteristic of floc lipids, in shrimp reared in mesocosms denoted their assimilation from the floc. Substitution of FO by olive oil in diets for shrimp reared in mesocosms did not affect growth or survival. Survival and growth of shrimp reared in mesocosms was better than those reared in clear water and fed an olive oil diet, whereas DHA or ARA enrichment of non-fish oil (NFO) diet improved survival of shrimp reared in clear water. Higher survival rate, triglyceride and DHA content in whole body and eyes of shrimp fed a DHA-rich diet suggests that under these conditions, in clear water, it is necessary to include at least 4.8 g kg )1 DHA in diet dry weight. ARA enrichment seemed to negatively affect growth. The nutritional contribution of the floc to shrimp in mesocosm culture reduces or eliminates the need for a dietary source of FO and illustrates the importance of DHA and ARA to enhance shrimp survival in clear water conditions. KEY WORDS

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Recent efforts have been made to culture marine shrimp in systems operating under low or zero‐water exchange and with decreased water salinity. The aim of this study was to investigate the impact of various salinity levels on qualitative and quantitative characteristics of the natural community and, more particularly, ciliated protozoa, and compare this information with shrimp growth and survival. Tanks with 9‰ salinity were characterized by a higher pH, but also by a significantly higher concentration of chlorophyll a (Chl a) per weight of suspended matter (1.93 ± 0.72 µg Chl a/mg TSS) than tanks with 18‰ (1.29 ± 0.68 µg Chl a/mg TSS) or 36‰ (1.37 ± 0.61 µg Chl a/mg TSS) salinity. Concentrations of ciliates (max 6000 cells mL−1) showed considerable fluctuations over the sampling period, reflecting the impact of water salinity, dynamic interactions between ciliates and their diverse roles within the shrimp production system. There was no significant difference between survival rates of shrimp reared at 9‰, 18‰ or 36‰, but decreasing salinity from 36‰ to 9‰ led to a significant decrease in final shrimp body weight (from 13.40 ± 0.26 g to 10.23 ± 2.72 g). Future work should address the potential of ciliates as an indicator of aquaculture water quality, as is currently being done in the wastewater industry, and the contribution of ciliates as food sources.

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