The availability of shelters in a specific density is expected to increase the production of mud crabs (Scylla serrata) in a recirculation system. Shelter, as one of the abiotic factors, plays a pivotal role in reducing death caused by cannibalism of crab and suppressing the stress levels of biota. Recirculation Aquaculture System (RAS), with the culture box capacity 60 L supported by the shelters, is predicted to produce the best physiological and growth responses of mud crabs. This present study aims to evaluate the effect of shelter addition in the environmental recirculation system on the physiological responses and production of mud crabs S. serrata with a density of 10 crabs per one culture box containing 60 L of seawater. The research was set up with three treatments of shelter addition, i.e., two shelters (S2), four shelters (S4), six shelters (S6), and control without shelter (C). Results showed that S6 was the best treatment with a survival rate of 73.33 ± 5.8%, a specific growth rate of 0.886 ± 0.014%, the growth rate of carapace width 0.024 ± 0.004 cm/day, and the lowest feed conversion ratio than those of other treatments. S6 treatment significantly influenced the total hemocyte count of crabs at the early cultivation (P <0.05). Addition of six shelters could optimize the growth of mud crabs with a stocking density of 10 crabs in one culture box.

Accumulation of organic matter derived from an uneaten feed, faeces, and other metabolic waste of biota can reduce water quality. This issue can be overcome by physical method using filtration systems such as malang sand. The present study aimed to identify the morphology and abundance of nitrifying and denitrifying bacteria in the mud crab Scylla serrata cultivation system treated with different weight of malang sand as i.e. 0 kg (control), 5 kg, 10 kg, 15 kg, and 20 kg. Mud crabs with the weight of 73.72±1.05 g and carapace length of 7.28±0.06 cm were reared in a container measuring 60 cm x 30 cm x 30 cm for 30 days fed two times a day using ad satiation method (as satisfied as possible). The results showed that a treatment using 5 kg malang sand was the best treatment with the survival rate of mud crabs reached 77.77±19.2%. At the end of cultivation period, nitrifying and denitrifying bacteria accounted for 1.52x107 CFU mL−1 and 1.06x107 CFU mL−1, respectively. The nitrifying and denitrifying bacteria in the rearing water were classified as Pseudomonas sp. and Acinetobacter sp., respectively.

Detection of bacterial diversity in whiteleg shrimps and its rearing water is a vital first step in monitoring aquaculture activities. Bacterial community imbalance in whiteleg shrimps and its rearing water influences the quality and quantity of shrimp production. Identifying the bacterial community provides basic information related to dominant bacterial groups in whiteleg shrimps and environments, providing recommendations for proper environmental monitoring and management. In this study, we investigated bacterial community structure in the rearing water and intestinal tract of whiteleg shrimp (Litopenaeus vannamei) collected from two sites, i.e., Pangkajene, South Sulawesi (SU) and Banyuwangi, East Java (BW), Indonesia. The bacterial community was analyzed using amplicon sequencing with Illumina sequencing platform based on the V3-V4 region of the 16S rRNA genes. Bacterial diversity and composition were found differed between the rearing water and the shrimps’ intestines. Bacterial diversity in the rearing water of Banyuwangi (W.BW) was higher than that of Pangkajene (W.SU). Proteobacteria, Bacteroidetes, and Firmicutes were found as the most dominant phyla in rearing water from both farms, while distinct bacterial composition was observed in the shrimps’ intestines. The shrimp intestine from Banyuwangi (U.BW) was dominated by Firmicutes (22.36%), Proteobacteria (22.33%), and Verrucomicrobia (21.11%). In contrast, the shrimp intestine from Pangkajene (U.SU) was highly dominated by Tenericutes (88.54%), followed by Proteobacteria (4.66%), and Firmicutes (2.27%). The difference in bacterial community structure between the rearing water and shrimps’ intestines suggested that the host intestinal environment might have greater selective pressure for bacterial composition inhabiting L.vannamei intestines. Our observations suggest that the shrimps cultured in the rearing water with the similar dominant bacterial group have specific intestinal bacterial diversity.

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Seawaters in Indonesia, part of the tropical marine ecosystem, have great microbial and plankton diversity. Seawater is used as a water source for marine aquacultures, such as shrimp, milkfish, lobster, and mud crab. Sustainability of environmental resources for supporting aquaculture activities can be assessed by analyzing the actual conditions of the water source environment, including bacterial and plankton communities. However, the characteristics of bacteria and plankton communities in Indonesian seawaters have not been well documented. In this study, we investigated the bacterial and plankton communities in surface seawater from two coastal areas, i.e. Nampu and Sembukan, Wonogiri regency, Central Java, Indonesia. Bacterial diversity was analyzed using the Illumina-based high throughput sequencing with a primer set targeting the V3-V4 region of the bacterial 16S rRNA gene. Meanwhile, the plankton community (phytoplankton and zooplankton) was calculated and identified using a counting chamber method. Sequencing analysis revealed that the five dominant bacterial phyla in the two seawater samples were similar, consisting of Proteobacteria, Firmicutes, Actinobacteria, Bacteriodetes, and Cyanobacteria. Although the two sites are separated by several kilometres, the distribution of dominant bacterial phyla in both seawater samples is similar. Phytoplankton in Nampu and Sembukan were similarly dominated by Trichodesmium sp., Navicula sp., and Rhabdonema sp. Dominant zooplankton in the two sites were Euterpina, Nauplius, Oithona sp., Oncaea sp., Tigriopus sp., and Gastropoda larvae. The seawater in Nampu and Sembukan is suitable as a water source for aquaculture.