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Optimization of three anoxygenic photosynthetic bacteria as feed to enhance growth, survival, and water quality in fairy shrimp (Streptocephalus sirindhornae) cultivation

2020; Elsevier BV; Volume: 534; Linguagem: Inglês

10.1016/j.aquaculture.2020.736288

1873-5622

Chewapat Saejung, Anuwat Chaiyarat, La‐orsri Sanoamuang,

Aquatic life and conservation

The fairy shrimp Streptocephalus sirindhornae has been commercially produced as a potential live feed to replace the use of brine shrimp in freshwater aquaculture. To determine an optimal diet for these fairy shrimp, the use of highly nutritious microorganisms that are relatively simple and cost effective to cultivate should be explored. In this study, the anoxygenic photosynthetic bacteria Rhodobacter sphaeroides, Rhodopseudomonas palustris, and Rhodopseudomonas faecalis PA2 were assessed for fairy shrimp cultivation, and the effect of dried bacterial biomass is reported. Fairy shrimp fed R. faecalis PA2 showed the highest survival and growth performance in both larval and adult experiments. At the adult stage, the survival and growth of fairy shrimp fed R. faecalis PA2 were higher than those of the control, whereas those fed R. sphaeroides complete died at 12 days of age. Dissolved oxygen (DO), ammonia, nitrite, and nitrate concentrations in the treatments containing photosynthetic bacteria were acceptable. The effects of air-dried (without sunlight) R. faecalis PA2 (AD) and freeze-dried R. faecalis PA2 (FD) on fairy shrimp were investigated and compared with those of commercial dried Spirulina (SP), a bacterial suspension of R. faecalis PA2 (BS), and a control treatment. The maximum survival rate and growth performance were observed in fairy shrimp fed BS; meanwhile, those fed AD, FD, and the control had similar results, which included slightly lower survival than those fed the BS. Surprisingly, the SP treatment group had the lowest survival rate and DO concentration as well as the highest ammonia concentration. Analyses of proximate composition showed that the nutritional values of AD and FD, particularly in terms of their protein and carbohydrate contents, were favorable for aquatic feeds. Our results suggest that R. faecalis PA2 may be used as a new feed for fairy shrimp to enhance growth and survival with no effect on water quality. Although the fresh form was superior, the dry form is also a satisfactory option if storage time is a concern.