Shrimp Culture Systems Research Articles

Bacterial Communities Associated With Penaeus vannamei Boone, 1931 Surface and Its Rearing Water in Biofloc Culture System

The biofloc system is an ecologically sustainable shrimp culture system. The conglomerates of beneficial bacteria, algae and protozoa in pond water serve as a water quality management system and as a feed additive to the shrimps. This study aimed to characterise the microbial communities associated with the biofloc pond water and the surface of Penaeus vannamei Boone, 1931, reared in it using the Illumina Miseq sequencing technology. The multiple alpha diversity measures indicated the shrimp surface samples to be richer in diversity than the pond water samples. Analysis of the bacterial community revealed that Proteobacteria, Bacteroidetes, Planctomycetes and Cyanobacteria formed the principal phyla. There was a shift in the relative abundance of bacterial communities at each time point. The operational taxonomic units (OTU) analyses revealed that 18.38 % OTUs were shared by the pond water samples, the shrimp surface samples shared 29.35 % at the three different time points. PICRUST analysis revealed that the bacterial communities in the biofloc rearing water, and shrimp surface, were likely involved in intensive microbial metabolism and core housekeeping functions. The information generated will help understand the bacterial community composition associated with optimal water quality and shrimp health in a biofloc culture system.

Finfish-Based Bioaugmentation Technology for Enhancing Shrimp Grower’s Income and Livelihood

Penaeid shrimp culture has become an important economic activity in many countries, particularly in Asia. However, environmental challenges and bacterial and viral disease outbreaks are being increasingly recognized as significant constraints on aquaculture production and trade worldwide. Diverse bacterial genera have been associated with infections of penaeid shrimp, but vibriosis is one of the mainly severe bacterial diseases which cause mortality, have been reported in penaeid shrimp culture systems. Tiger shrimp Penaeus monodon and white shrimp Penaeus vannamei are susceptible to fatal effects of luminous vibriosis in India, creating economic losses. There is always a need to control Vibrio harveyi in brackish water shrimp aquaculture. Green water culture system is a biological approach, which integrates the culture of economically important euryhaline finfish as bioaugmentors in the reservoir or net cages/pens in the shrimp growing ponds through zero-water exchange and recirculatory system. The secretions of slime enhance the production of green water which not only suppress the proliferation of luminous bacteria, but also improves the water quality by removing nutrient. In this paper, a hypothesis has been proposed to utilize green water technology as a bioaugmentation technology based on integration of fish green slime beneficial bacteria and their bioactives for controlling priority pathogens in freshwater and brackish water shrimp aquaculture systems for achieving higher shrimp production and enhancing farmers income and livelihood.

Using lactic acid bacteria as an immunostimulants in cultured shrimp with special reference to Lactobacillus spp.

Shrimp aquaculture is the rapidly growing sector of fish culture producing sectors in the world due to its rising demand in developed countries. Moreover, the intensive and extensive shrimp culture systems are affected mainly by infection diseases caused by several pathogenic agents and resulting in high economic losses. Nowadays, controlling and preventive infection diseases are the major concern to develop this sector. Besides, the highly extensive usage of chemotherapeutics and antibiotics induced numerous drawbacks in shrimp farming, developed antibiotic resistance bacterial strains, and threatens the aquatic life. Recently, improving the immunity status and controlling infectious diseases using biological methods have become beneficial, environment friendly, and risk-free options in aquaculture. Probiotics have gained much attention as immunostimulants in aquaculture owing to their inhibitory properties on pathogenic microorganisms via creation of an unfriendly atmosphere to cease their growth. Lactobacillus species as probiotics was used in shrimp aquaculture to prevent viral infections due to their positive promoting effects on survival and health. Additionally, Lactobacillus species possesses sturdy antimicrobial activity against various pathogenic microorganisms such as Photobacterium and Vibrio infections. This review threw the light on the applications of Lactobacillus sp. as probiotics in cultured shrimp which could be of great impact from a sustainable, intensive, and ecofriendly aquaculture opinion.

Characteristics of Ammonia Removal and Nitrifying Microbial Communities in a Hybrid Biofloc-RAS for Intensive Litopenaeus vannamei Culture: A Pilot-Scale Study

Ammonia is the main pollution factor of the aquatic environment in marine shrimp culture systems. In order to demonstrate the feasibility of the combination of biofloc technology and nitrifying biofilter for the ammonia removal, a 70-day production trial was conducted in a simplified pilot-scale hybrid biofloc-based recirculating aquaculture system (biofloc-RAS) with the intensive culture of Litopenaeus vannamei. Nitrogen dynamics and nitrifying microbial communities were investigated in three replicated systems simultaneously under the conditions of high feed loading and zero water exchange. Along with biofloc development in the culture tank and biofilm formation in the nitrifying biofilter during the trial, nitrification could be fastly and effectively established in the system, which was indicated by the dynamics of total ammonia nitrogen (TAN), NO2–-N, NO3–-N, and total nitrogen (TN) concentrations. Meanwhile, similar nitrifying microorganisms could be found between biofloc and biofilm, despite some differences in abundance, diversity, and composition of ammonia-oxidizing archaea and bacteria and nitrite-oxidizing bacteria. High TAN removal rate could be achieved and was significantly and positively correlated with abundances of these nitrifying microbial communities in both biofloc and biofilm, further indicating that both biofloc and biofilm could contribute highly to nitrification performance of the biofloc-RAS. The results of this study indicate a potential application of the biofloc-RAS in coastal intensive aquaculture.

Effects of carbohydrate sources on a biofloc nursery system for whiteleg shrimp (Litopenaeus vannamei)

In biofloc technology carbohydrate is added to stimulate the biofloc growth, the latter helps to improve water quality, reduce the need for water exchange and may serve as natural shrimp feed. The large diversity among possible carbohydrate sources makes the selection of a suitable carbohydrate difficult. This study investigated how corn starch addition compared to molasses addition affected water quality, biofloc and periphyton proximate composition, shrimp production parameters, diurnal fluctuations and distribution of carbon and nitrogen in whiteleg shrimp (Litopenaeus vannamei) culture system. The results showed that both corn starch and molasses addition treatments resulted in low ammonium nitrogen levels in the water. The total suspended solids and volatile suspended solids in both treatments increased over time and were not significantly different among treatments. The protein content in the dry matter of the biofloc varied from 34% to 48%, being higher in the molasses treatment. The same was observed for the protein content in the dry matter of the periphyton which ranged between 16% and 26%. The corn starch treatment resulted in significantly higher shrimp growth rate, production, average body weight, and lower FCR compared to molasses addition. Water quality was stable on a daily basis, but changed over the weeks. Carbon and nitrogen accumulations in the system were not significantly different among treatments.

Essential oils mediated antivirulence therapy against vibriosis in Penaeus vannamei

The emergence of new virulent Vibrio strains resistant to common antibiotics has caused significant economic losses to shrimp farming worldwide. It is mandatory to adopt new strategies to control shrimp farming related vibriosis. Essential oils (EOs) have several biological properties among of which the quorum sensing (QS) inhibitory activity is appealing for vibriosis control. In this work, we evaluated QS inhibitory activity of five EOs obtained from oregano (Organum vulgare), tea tree (Melaleuca alternifolia), lemongrass (Cymbopogon citratus), cinnamon (Cinnamomum verum) and thyme (Thymus vulgaris), at sublethal doses. EOs involvement in bioluminescence shutdown, biofilm formation and swarming motility was evaluated in four Vibrio strains of aquaculture interest including V. harveyi, V. campbellii, V. vulnificus, and V. parahaemolyticus. Oregano oil (EOOv) and tea tree oil (EOMa) were further tested in in vivo assays due to their significant effects (P < 0.05) on QS inhibition. EOOv was the most efficient one and exerted a comparable QS inhibitory effect to EOMa at a lower concentration in vivo (2.5 μg mL−1 of EOMa versus 1.0 μg mL−1 of EOOv). The lowest active doses of EOOv and EOMa that inhibited QS had no toxic effects on hemocytes and larvae of P. vannamei. A challenge test was performed in P. vannamei postlarvae (PL8) with V. campbellii, grown previously in the presence of EOOv or EOMa at sublethal active doses. Our results indicated that both EOs affected the virulence of V. campbellii and were able to significantly (P < 0.05) reduce shrimp mortality (EOOv in a 40% while EOMa in a 32%). A field bioassay was also carried in earthen ponds to test two different concentrations of EOOv and EOMa for feed supplementation (2.5 and 5.0 mg kg−1 respectively). EOOv increased significantly (P < 0.05) shrimp survival and yield at both doses, whereas EOMa increased shrimp survival and yield only at the highest dose. In conclusion, EOOv and EOMa constitute suitable alternatives to reduce vibrios virulence and to increase yield in shrimp culture systems.

Prevalence of white spot virus and monodon baculovirus in shrimp culture systems of West Bengal, India

The global shrimp aquaculture is impacted by episodes of viral diseases resulting in huge income losses. This communication presents the results of the polymerase chain reaction (PCR) based surveillance of white spot virus (WSV) and monodon baculovirus (MBV) in shrimp culture systems of West Bengal, India. The WSV was detected in 14.87% of the total samples (N = 121) by first PCR and 16.53% of samples by nested PCR. The WSV infection was noticed in 12 of 65 Penaeus monodon, 6 of 39 Litopenaeus vannamei and 2 of 11 Macrobrachium rosenbergii samples. The MBV was detected in 8 of 65 P. monodon samples by non-nested PCR and all were also positive for WSV, thus indicating concurrent infection of shrimp. The results emphasized the need to observe strict quarantine measures during the seed selection to prevent the introduction of viral pathogens in grow-out systems.

Effect of Algae Decaying on Shrimp Culture System and Suggested Biological Remediation Strategies

Pond water with algae blooms was collected, and maintained in the dark over a 2-day period without nutritional supplements. The physico-chemical parameters and the density of algae were measured. The concentration of NH 4+-N, DIN and PO4–P in water in darkness significantly increased, and the density of algae decreased significantly. Isolated water was exposed to three bio-remediation water treatments: addition of green algae, Bacillus subtilis and photosynthetic bacteria. After remediation, the concentrations of NH4+ -N, NO3- -N, DIN and PO4- -P in the three treatment groups were significantly lower than the control group. No difference was observed in the concentration of NO2–N between the control group and the photosynthetic bacteria group. Results from all treatments showed water quality deterioration along with increase in nitrogen and phosphorus concentrations. Bio-remediation methods can be effectively adapted in shrimp culture after algae decay, and one of the most promising biological remediation strategies is the use of green algae.

Temporal patterns of bacterial communities in shrimp (Litopenaeus vannamei) culture systems loaded with oyster shells

Oyster (Crassostrea gigas) shell-loading in aquaculture systems can regulate water quality, a critical factor for Litopenaeus vannamei growth. However, the effects of oyster shell-loading on the bacterial community composition and their interactions during shrimp culture processes remain elusive. Here, 16S rRNA gene amplicon sequencing was used to investigate the dynamics and co-occurrence patterns of bacterial communities in L. vannamei culture systems loaded with oyster shells. The results indicated that oyster shell-loading significantly improved both shrimp survival and water quality. Oyster shell-loading was found to cause a significant increase in the relative abundance of Alphaproteobacteria (P < .05), whereas the relative abundances of Actinobacteria, Deltaproteobacteria, and Cyanobacteria decreased significantly. Mantel test and partial least squares path modeling analysis revealed that oyster shell-loading was closely related to changes of water variables, especially total ammonia nitrogen (TAN) and chlorophyll-a; water temperature and salinity were the most important physical factors driving bacterial community variation. The co-occurrence networks in the control and oyster shell-loading groups were mainly occupied by Flavobacteriaceae and Rhodobacteraceae, and more complex microbial interactions were found in the oyster shell-loading group. This study is the first report on the effects of oyster shell-loading on bacterial community dynamics and co-occurrence patterns in aquaculture systems. These findings are important steps towards clarifying the biological mechanisms of oyster shell-loading on shrimp growth.

Bioprospecting of an Indigeneous Bacillus thuringiensis Strain G5-8-3T02 for Shrimp Culture System

Aim: An indigenous Bacillus thuringiensis strain G5-8-3T02 earlier isolated from healthy shrimp intestine and established to safeguard Penaeus monodon from Vibrio mimicus infection was assessed as a potential candidate bacterium for drug enhancement for shrimp culture systems.&#x0D; Methodology: Optimal temperature, pH and salinity for growth and antibacterial activity of Bacillus thuringiensis against Vibrio mimicus were determined. The effects of enzymes (pepsin, catalase, lipase and α- amylase), pH (2-9), heat (37°C – 121°C) and surfactants (Sodium dodecyl sulphate and Tween 80) on antibacterial activity were also evaluated. Cell growth and antibacterial activity were monitored daily for 5 days via spectrophotometric method at 600 nm and agar well diffusion assay respectively. The metabolite extracted with methanol was analyzed for bioactive compounds using Gas Chromatography-Mass Spectrometry (GC-MS).&#x0D; Results: The optimum temperature, pH and salinity for growth and metabolite production were 35°C, pH 6-7 and 10-15 ppt. respectively. The crude extract did not totally lose its activity when treated with enzymes, various pH values, heat and surfactants. The quantitative composition of the metabolite revealed 15 bioactive compounds. The main compound produced was 2, 6, 10-Trimethyltridecane with peak area of 14.58%.&#x0D; Conclusion: The non-pathogenic, antagonistic, indigenous Bacillus thuringiensis strain G5-8-3T02 could be engaged in the management of vibriosis in shrimp culture since the use of antibiotics in aquaculture for disease control yields objectionable effects. The identified bioactive compounds might be valuable for drug development for shrimp culture system.

Effect of biofloc density and crude protein level in the diet on the growth performance, survival rate, and feed conversion ratio of Black Tiger Prawn (Penaeus monodon)

The objectives of the present study were to evaluate the best combination of biofloc density in culture media and percentage crude protein content on feed on growth performance, survival rate and feed utilization of the black tiger shrimp (Penaeus monodon) culture system. The Completely Factorial Random Design (CFRD) was used in this study. The first tested factor is the percentage of crude protein in the diet at three levels namely; 35%, 30%, 25%, and the second factor is biofloc density at in three levels namely; 5mlL−1, 10mlL−1, 15 ml L−1. The results showed that the combination of 35% crude protein combined with 10mlL−1 biofloc gave the best results for all measured parameters, with a survival rate of 100%, absolute growth rate was 17.207g, daily growth rate was 0.58g day−1, specific growth rate was 3.528% day−1, feed conversion ratio (FCR) was 0.974, and the feed efficiency was 102.7%. It is concluded that the best combination of crude protein and biofloc density that 10 ml L−1 floc and 35% crude protein diet.

Successional changes of microalgae community in response to commercial probiotics in the intensive shrimp (Litopenaeus vannamei Boone) culture systems

Probiotics with antimicrobial properties can be used to regulate the microflora, control the pathogenic algae, and improve the mineralization of organic substances in the aquaculture environment. However, the efficacy of the probiotics on the succession of microalgae in the shrimp (Litopenaeus vannamei Boone) culture remains inadequate. A field experiment in mesocosm was performed to explore the impacts of probiotics on the succession of microalgae and nutrient enrichment of the shrimp culture systems. The enormous changes in the microalgae community structure (MCSs) was significantly influenced by probiotic colonization. Probiotics shifted MCSs into three seral phases and their sequential replacements of the dominant taxa were identified by cluster analysis. Moreover, each seral stage of the keystone species turnover in MCSs represents distinguished ecological functions. At the final seral stage probiotics significantly constrained the succession of the most competitive species of Cyanobacteria (Oscillatoria and Anabaena) which was disagreed with the normal seral stage. Similarly, the probiotics increased and maintained the sequel of the nutritional value of Nannochloropsis and Chlorella from Chlorophyta and Oocystics and Navicula from the Bacillariophyta. Furthermore, the probiotic-based ponds had a higher shrimp survival rate compared to the control. Nutrients concentration of nitrite (NO2−) and nitrate (NO3−) were lower in treatments than in the control. Consequently, chemical oxygen demand (COD), nitrite (NO2−), water temperature (WT), total ammonium nitrogen (TAN) and dissolved oxygen (DO) were strongly explanatory variables controlled the sequel of MCSs. These findings imply that the probiotics have potential in the succession, redistribution of beneficial microalgae, inhibit the growth of harmful Cyanobacteria and sustain the MCSs stability in shrimp aquaculture activities.

Effects of the algicidal bacterium CZBC1 on microalgal and bacterial communities in shrimp culture

AEI Aquaculture Environment Interactions Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections AEI 11:279-290 (2019) - DOI: https://doi.org/10.3354/aei00311 Effects of the algicidal bacterium CZBC1 on microalgal and bacterial communities in shrimp culture Xiaojuan Hu**, Guoliang Wen**, Wujie Xu, Yu Xu, Haochang Su, Keng Yang, Yunna Xu, Zhuojia Li, Yucheng Cao* Key Laboratory of South China Sea Fishery Resources Exploitation and Utilization, Ministry of Agriculture and Rural Affairs; Key Laboratory of Fishery Ecology and Environment, Guangdong Province; South China Sea Fisheries Institute, Chinese Academy of Fishery Sciences, Guangzhou 510300, PR China *Corresponding author: cyc_715@163.com**These authors contributed equally to this work ABSTRACT: Algicidal bacteria may play a role in controlling algal blooms. Previously, a Bacillus cereus strain (CZBC1) was shown to have specificity against harmful Cyanophyta. To elucidate the characteristics of microalgal and bacterial communities in shrimp culture associated with the algicidal bacterium CZBC1 and its combined use with the addition of organic carbon, we established a shrimp culture system in which the dominant macroalgal species were Oscillatoria chlorina (Cyanophyta) and Chlorella pyrenoidosa (Chlorophyta). We studied water-column microalgal and bacterial communities in control (GC), bacteria (GB), and bacteria-carbon (GBC) treatment groups at the mid-point (Day 28) and end (Day 56) of the experiment. The algicidal bacterium CZBC1 was able to regulate abundance of Cyanophyta on Days 28 and 56 in GB and GBC. Abundances of Cyanophyta on Days 28 and 56 ) in GB (<0.44%) and GBC (<0.37%) were significantly lower than that in GC (25.58 to 40.87%), and those of Chlorophyta in GB (86.83 to 92.85%) and GBC (99.63 to 99.94%) were significantly higher than those in GC (52.52 to 67.35%). Multiple linear stepwise regression analysis showed that the amount of applied algicidal bacterium CZBC1 had the most significant negative correlation with the abundance of Cyanophyta (R = 0.973, p < 0.01). On Days 28 and 56, the average well color development value (Biolog), bacterial count, and bacterial community structure were relatively stable in GB, while the addition of a carbon source increased the amount of bacteria and affected the composition of the bacterial community in GBC. Our findings suggest that algicidal bacteria can be used to regulate microalgal communities and stabilize the metabolic potential of bacterial communities in aquaculture. KEY WORDS: Algicidal bacteria · Dominant species of microalgae · Bacterial communities · Carbon source · Cyanophyta Full text in pdf format PreviousNextCite this article as: Hu X, Wen G, Xu W, Xu Y and others (2019) Effects of the algicidal bacterium CZBC1 on microalgal and bacterial communities in shrimp culture. Aquacult Environ Interact 11:279-290. https://doi.org/10.3354/aei00311 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AEI Vol. 11. Online publication date: June 27, 2019 Print ISSN: 1869-215X; Online ISSN: 1869-7534 Copyright © 2019 Inter-Research.

Diversity and bacterial succession of a phototrophic biofilm used as complementary food for shrimp raised in a super-intensive culture

Biofilm-based systems for shrimp aquaculture have emerged as a novel alternative to improve the water quality and obtain a better performance into ponds using zero or limited water exchange. The aims of this work were (1) to evaluate the production response and water quality of a super-intensive shrimp culture using a phototrophic biofilm as complementary food and (2) to study the bacterial diversity of these biofilms. A trial was performed, consisting of a shrimp culture system using biofilms as food source and a control without biofilms. Results showed that the biofilm-based system had better water quality and shrimp registered a higher growth performance compared to the control. Regarding the taxonomic profile of bacterial populations detected in the biofilm, results revealed that Proteobacteria, Bacteroidetes, and Planctomycetes were the three most abundant phyla; of these, eight bacterial orders belonging Rhizobiales, Clostridiales, Cytophagales, Actinomycetales, Vibrionales, Flavobacterales, Planctomycetales, Chlamydiales, and Rhodobacterales constituted a microbial core maintained over time. Some of these are related to anaerobic and aerobic removal processes of nitrogen. The results of this study are a first approach to understand how the bacterial communities forming biofilms are related to water quality of ponds and production performance of aquaculture farms, and how the microbial succession may cause changes on the taxonomic profile biofilms.

Ammonia-oxidizing bacterial and archaeal communities in tropical bioaugmented zero water exchange shrimp production systems

Ammonia oxidation is an important process in the removal of ammonia generated from feed and metabolic wastes in aquaculture systems. Considering the biogeochemical importance of ammonia oxidation in bioaugmented zero water exchange aquaculture systems, the diversity and abundance of bacterial and archaeal ammonia-oxidizing communities were analyzed in three selected ponds at different time intervals during the culture period, to unravel the key environmental factors influencing their distribution in the system. The diversity and abundance of ammonia-oxidizing bacteria (AOB) and archaea (AOA) in three tropical bioaugmented zero water exchange (ZWE) shrimp culture systems were analyzed using ammonia monooxygenase A (amoA) gene from the sediment metagenome during different phases of culture. The environmental factors associated with the variability in bacterial and archaeal amoA gene abundance and diversity were elucidated using RDA and Pearson correlation analysis. Ammonia-oxidizing archaea (AOA), Nitrosopumilus sp., Nitrosospharea sp., and ammonia-oxidizing bacteria (AOB), Nitrosomonas sp., were the dominant ammonia-oxidizing communities in the ZWE ponds studied. AOA shared 41 OTUs, and the maximum distribution was influenced by dissolved oxygen in the system, whereas AOB shared 4 OTUs. The copy numbers amoA gene determined using qPCR showed that the AOA amoA gene was 10- to 100-fold abundant than AOB amoA gene. Gene abundance of AOA was positively related to total organic carbon (TOC) and salinity of sediments, and the temperature had a negative impact on bacterial amoA gene abundance. The dissolved oxygen and TOC had a negative and redox potential a positive impact on the diversity of AOA, whereas pH had a negative impact on the diversity of AOB. The ammonia-oxidizing archaeal communities dominated the bioaugmented zero water exchange aquaculture systems compared to bacteria based on the abundance and diversity analysis using amoA gene sequence-based OTU analysis and gene copy numbers. Dissolved oxygen, total organic carbon, and Eh of the sediments contributed to the distribution and abundance of AOA group in the ZWE ponds. This study points to the importance of environmental management in these culture systems for maintaining ammonia-oxidizing populations for optimal ammonia removal. The relative contribution of the archaea and bacteria to ammonia oxidation in these systems is to be further resolved along with that of anammox and comammox bacteria, which would help to develop appropriate biostimulation or bioaugmentation strategies for the management of these sustainable aquaculture production systems.

Effects of a Commercial Microbial Agent on the Bacterial Communities in Shrimp Culture System

Commercial microbial agents (e.g., probiotics, microbial products, microorganism preparation et al.) have been widely applied for disease control in shrimp culture. However, the effect of these microbial agents (MA) on shrimp health is unstable and the underlying mechanism remains unclear. The effect of MA can probably be achieved by influencing the bacterial community of shrimp culture system. To test this hypothesis, we used 16S rRNA gene amplicon sequencing to investigate the dynamics of both planktonic and intestinal bacterial composition in shrimp culture ponds with or without commercial MA applied weekly. The results showed that MA application increased the temporal turnover rate of bacterioplankton community. Within 1 week, MA-treatment significantly drove bacterioplankton community composition to divert from that without MA-treatment at day 2 after MA application, but the deviation tended to vanish at days 4 and 7. At day 21, a significant difference was observed in shrimp intestinal bacterial community between two groups. The relative abundance of Rhodobacteraceae in shrimp intestine was significantly greater in the MA-treated group than that in the control. However, MA-treatment did not significantly improve the growth or survival ratio of shrimp. This study suggest that MA works in terms of accelerating bacterioplankton community turnover and shifting intestinal bacterial community, however, its effect on shrimp growth might vary greatly and might be improved by optimizing the method in activation and application and more investigation on the microbial ecological process of shrimp culture system is needed before we develop and apply probiotics more efficiently.

A new strain of white spot syndrome virus affecting Litopenaeus vannamei in Indian shrimp farms.

White spot syndrome virus (WSSV)-infected shrimp samples collected from grow-out ponds located at Nellore, Andhra Pradesh, India, showed WSSV negative and positive by PCR using primer sets specific to ORF119 and VP28 gene of WSSV, respectively. This indicated the deletion of genetic fragments in the genome of WSSV. The WSSV isolate along with lab strain of WSSV was subjected to next-generation sequencing. The sequence analysis revealed a deletion of 13,170 bp at five positions in the genome of WSSV-NS (new strain) relative to WSSV-TH and WSSV-LS (lab strain). The PCR analysis using the ORF's specific primer sets revealed the complete deletion of 10ORFs in the genome of WSSV-NS strain. The primer set was designed based on sequence covering ORF161/162/163 to amplify a product of 2,748bp for WSSV-LS and 402bp for WSSV-NS. Our surveillance programme carried out since 2002 revealed the replacement of WSSV-LS by WSSV-NS in Indian shrimp culture system.

Effects of two commercial feeds for semi-intensive and hyper-intensive culture and four C/N ratios on water quality and performance of Litopenaeus vannamei juveniles at high density in biofloc-based, zero-exchange outdoor tanks

A two-factor experiment was conducted to evaluate the effects of two commercial shrimp feeds and four different C/N ratios on biofloc development, water quality, growth performance, feed utilization and input cost in an outdoor tank system stocked with Litopenaeus vannamei juveniles under high-density and zero-exchange conditions. The two feeds used in the study were: a less expensive feed (US$0.99 kg−1) formulated for semi-intensive production systems and a more expensive one (US$1.75 kg−1) designed for hyper-intensive systems. Organic carbon (molasses) was added daily to provide calculated carbon to nitrogen (C/N) ratios of 12:1, 15:1, and 18:1 based on the carbon-nitrogen content of the feed and the carbon content of the molasses throughout the experiment. No molasses was added in the control group which had a C/N ratio of 9:1. Each treatment had four randomly assigned replicate tanks, and each tank filled with 500 L of biofloc-rich water. Juvenile shrimp (2.21 ± 0.11 g) were stocked into tanks at 150 shrimp tank−1 (300 juveniles m−3) and cultured for six weeks. The results showed that both feed and C/N ratio had significant effects on biofloc development, water quality, shrimp performance, feed utilization and input cost. Initiating the culture with biofloc-rich water and then adding a small amount of organic carbon regularly could effectively sustain the continued development of mixotrophic bioflocs in zero-exchange high-density shrimp culture systems. The best water quality, shrimp performance, and FCR results were achieved with the C/N ratio of 12:1 for both feeds. Analysis of feed and variable costs suggest improved economic benefits when using the less expensive feed of SI-35 under the conditions of this study. Furthermore, input costs could be decreased using a C/N ratio of 12:1 due mainly to reduced molasses and NaHCO3 usage.

Marine actinomycetes as bioremediators in Penaeus monodon rearing system

Actinomycetes (277 Nos) isolated from marine environment and shrimp culture pond sediments were tested for hydrolytic enzyme production and biogranulation property. Potential isolates were screened for their efficacy in bioremediation of shrimp culture system. Based on the BOD reduction efficiency and water quality parameters, five actinomycete isolates viz., Streptomyces coelicoflavus (A6), Streptomyces diastaticus (A44), Nocardiopsis alba (A55), Streptomyces parvus (A56) and Streptomyces champavatii (R32) were subjected for tertiary screening in Penaeus monodon larval rearing system and the animals were challenged with white spot syndrome virus (WSSV). The bioremediating effect of actinomycete treatments were assessed by analysing the expression profile of five antimicrobial peptide (AMP) genes viz., anti-lipopolysaccharide factor (ALF), crustin-2, crustin-3, penaeidin-3 and penaeidin-5 and eight immune genes viz., alpha-2-macroglobulin (α-2-M), astakine, glutathione-S-transferase, haemocyanin, peroxinectin, pmCathepsinC, prophenol oxidase (proPO) and Rab-7. Expression of eight WSSV genes viz., DNA polymerase, endonuclease, protein kinase, immediate early gene, latency related gene, ribonucleotide reductase, thymidine kinase and VP28 were also analyzed to detect the presence and intensity of viral infection in the experimental animals post-challenge. Theapplication of consortia (1 g/5 L water) yields better results in terms of significant reduction in BOD of shrimp rearing system showing the bioremediation potential of the marine actinomycete strains. The application of marine actinomycetes viz., Streptomyces coelicoflavus (A6), Streptomyces diastaticus (A44), Nocardiopsis alba (A55), Streptomyces parvus (A56) and Streptomyces champavatii (R32) in granulated form were found to be potential bioremediators in shrimp rearing system.

Occurrence of white spot syndrome virus and Vibrio parahaemolyticus in brackishwater shrimp culture systems of Sundarban, West Bengal, India

White spot disease (WSD) and acute hepatopancreatic necrosis disease (AHPND) are two important and highly fatal diseases of cultured shrimps. The occurrence of white spot syndrome virus (WSSV) was found to be very high in brackishwateraquaculture systems of Sundarban area in West Bengal, with 40.6% of the samples being positive of which 18.75% being positive in the first step PCR. The prevalence of WSSV in traditional and semi-intensive culture systems was foundas 59.3 and 27%, respectively. On the other hand, presence of Vibrio parahaemolyticus was detected in 53.1, 55.5 and 75.9% of the shrimp, water and soil samples, respectively. All the isolates of V. parahaemolyticus contained toxR gene as detected by PCR. However, none of the isolates was realised as AHPND causing isolate by PCR. Moreover, tdh gene, which causes gastroenteritis in human beings, was also not detected in any of the isolates. The present study indicated that WSSV is the major cause of crop failure in the brackishwater shrimp culture systems of Sundarban, India. Although,V. parahaemolyticus is highly prevalent in brackishwater shrimp culture systems of Sundarban, strains causing gastroenteritis or AHPND were not detected during the present study.