The world aquaculture industry seeks sustainable production strategies to respond to the needs of the growing world population for valuable food. Biofloc technology (BFT) is accepted as a novel sustainable method that reduces the pollution load on receiving water resources with its zero-water-discharge approach, eliminates extra water treatment costs with its biological cycles, and supports the growth performance of reared animals and thereby reduces feed costs. However, each BFT system has its own set of difficulties and obstacles. This review focuses on the advantages and disadvantages of BFT systems in terms of economy, sociability and applicability. The BFT shows more effective results in the conversion of toxic nitrogenous compounds to nontoxic compounds compared with the technologies based on nitrification processes. In addition, the growth performance and health of the cultured animals are generally better in BFT systems than those in conventional rearing systems (continuous water flow). The risk of common diseases occurrence due to pathogenic microorganisms appears to be lower in BFT systems compared to conventional aquaculture. It is also noteworthy that the immune system, biochemical stress indicators and antioxidant activities of organisms held in BFT systems are positively affected. In BFT systems based on microbial activity, the high water temperature demanded by bacteria is a limiter for the system. Moreover, a higher aeration/energy requirement is the case in BFT to meet the oxygen demand of all organisms including fish, shrimp, heterotrophic bacteria, nematodes, rotifers and others inside. There is also another concern about the acceptability potential of the cultured organism in BFT systems for consumption. Finally, since the high temperature demand of the system will create high energy costs, it should be considered as another restriction that forces the application. Considering the advantages and disadvantages of BFT systems as sustainable aquaculture, this review provides a guide for future studies and full-scale implementations.
The present study aimed to evaluate the effects of poly‐β‐hydroxybutyrate (PHB)‐supplemented diets for rainbow trout (Oncorhynchus mykiss) fingerlings. For this purpose, three experimental diets were prepared to contain 0, 2, and 5% PHB; and each diet was tested in a completely randomized design for 60 days in quadruple groups of 22 fish per tank. The results showed that the inclusion of PHB in the diets did not affect the growth parameters such as mean weight gain, specific growth rate, and feed conversion ratio among treatments. There was also no effect of the PHB on chemical composition, PCR‐DGGE profile of the intestinal bacterial communities, total bacterial count, lactic acid bacteria, psychrophilic bacteria as well as the intestine and the liver histopathology of fish. However, the supplementation of 2 and 5% PHB in the diet significantly reduced total coliform counts, while 5% PHB diet additionally decreased Enterobacteriaceae counts. Both inclusion ratios resulted in significantly higher intestinal villus length and width at the end of the experiment. Considering the positive effects of dietary PHB on intestinal bacterial flora and villus sizes of rainbow trout fingerlings, it can be used as an alternative microbial control agent. Significance Statement PHB is a biopolymer that has previously been reported to have positive effects on fish health, and no literature has been encountered investigating the effects of PHB on rainbow trout fry. The findings obtained in this study show that PHB has positive effects on the intestinal tissues of rainbow trout fry and provides an increase in the number of beneficial bacteria in the gut flora.
The Russian sturgeon (Acipenser gueldenstaedtii) species is in high demand owing to its valuable caviar. Therefore, it is in danger of extinction. Since the Russian sturgeon reaches sexual maturity late in its life cycle, this species has a high economic cost for farmers. However, this high cost can be reduced with an environmentally friendly system called biofloc technology. This study compared the growth performance and health indicators of biofloc groups using different carbon sources such as starch (BS), molasses (BM) and dextrose (BD). In the 60-day study, fish with an average initial weight of 106.44±5.79 g were stocked in tanks at a density of 21 fish/tank (0.4 m3/tank). The water temperature was set at 19 ℃ degrees throughout the study. On the 30th and 60th days of the experiment, fish were weighted to measure the growth parameters and sampled for immune indices. No mortality was observed in any group throughout the study. A between group comparison of weight gain revealed that BS and BM (105.51±2.26; 100.50±2.18) performed better than the control (BC, without external carbon sources) and BD groups (95.90±2.09; 87.36±2.18) (P<0.05). Furthermore, FCR and SGR were calculated from the data obtained at the end of the experiment, and the data shows that the BS and BM groups were statistically more effective than the other groups. Moreover, a comparison of NBT, lysozyme and myeloperoxidase enzyme activities indicated that all BFT groups had a stronger immune system than the control group (P<0.05). According to the results, the immune-enhancing effect of BFT for sturgeon was determined, and it was reported that BS and BM are more suitable for use in this species in terms of FCR and SGR, as they result an economic and environmentally friendly production.
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