Shrimp Aquaculture System Research Articles

Resilience, political ecology, and well-being: an interdisciplinary approach to understanding social-ecological change in coastal Bangladesh

The commodification of peasant livelihoods through export-oriented aquaculture has brought about significant social-ecological changes in low-lying coastal areas in many parts of Asia. A better understanding of the underlying drivers and distributional effects of these changes requires integration of social and ecological approaches that often have different epistemological origins. Resilience thinking has gained increased traction in social-ecological systems research because it provides a dynamic analysis of the cross-scalar interactions between multiple conditions and processes. However, the system-oriented perspective inherent in resilience thinking fails to acknowledge the heterogeneous values, interests, and power of social actors and their roles in navigating social-ecological change. Incorporation of political ecology and well-being perspectives can provide an actor-oriented analysis of the trade-offs associated with change and help to determine which state is desirable for whom. However, empirical demonstrations of such interdisciplinary approaches remain scarce. Here, we explore the combined application of resilience, political ecology, and well-being in investigating the root causes of social-ecological change and identifying the winners and losers of system transformation through empirical analysis of the differential changes in farming systems in two villages in coastal Bangladesh. Using the adaptive cycle as a structuring model, we examine the evolution of the shrimp aquaculture system over the past few decades, particularly looking at the power dynamics between households of different wealth classes. We found that although asymmetric land ownership and political ties enabled the wealthier households to reach their desired farming system in one village, social resilience achieved through memory, leadership, and crisis empowered poorer households to exercise their agency in another village. Material dimensions such as improved living standards, food security, and cash incomes were evidently important; however, freedom to pursue desired livelihood activities, better environmental quality, mental peace, and cultural identities had significant implications for relational and subjective well-being.

Dynamics of phytoplankton communities in eutrophying tropical shrimp ponds affected by vibriosis

Tropical shrimp aquaculture systems in New Caledonia regularly face major crises resulting from outbreaks of Vibrio infections. Ponds are highly dynamic and challenging environments and display a wide range of trophic conditions. In farms affected by vibriosis, phytoplankton biomass and composition are highly variable. These conditions may promote the development of harmful algae increasing shrimp susceptibility to bacterial infections. Phytoplankton compartment before and during mortality outbreaks was monitored at a shrimp farm that has been regularly and highly impacted by these diseases. Combining information from flow cytometry, microscopy, pigment and phylogenetic analysis, the presence of Picocyanobacteria, Prasinophyceae and Diatomophyceae were detected as dominant phytoplankton groups and Cryptophyceae, Prymnesiophyceae and Dinophyceae as minor components. At the onset of the first shrimp mortalities, Bacillariophyceae increased while Cyanobacteria, Prymnesiophyceae and Dinophyceae decreased in the water column, followed by proliferation of Prasinophyceae. Several taxa were identified as potential harmful algae (Cyanobacteria, dinoflagellates and Phaeocystis).

Bacterial diversity studied by next‐generation sequencing in a mature phototrophic Navicula sp‐based biofilm promoted into a shrimp culture system

The bacterial diversity of a phototrophic biofilm used as nutrient-recycler into a shrimp aquaculture system and as direct food-source for shrimp was studied by next-generation sequencing, considering the 16S rDNA and metagenomics sequence classification using exact alignments. Biofilm was promoted by the modification of cabon:nitrogen ratio and by the addition of the diatom Navicula sp. as promoter. Results revealed a wide diversity of bacteria thriving into the biofilm; most of the bacteria detected in the biofilm belonged to the Proteobacteria (47%), Chlamydiae/Verrucomicrobia (11%), Bacteriodetes (8%), Planctomycetes (5%) Phylum. Species involved in the decomposition of organic matter, nitrogenous- and sulfurous metabolites were detected; moreover, filamentous species known as biomass-bulking enhancers and producers of adhesin-like compounds were also detected. Surprising results were also obtained by detecting both, strictly anaerobic and aerobic bacteria involved into the metabolism of nitrogenous compounds. Other species not belonging to the marine environment were also detected, but their role is unclear. Finally, the detection of most of these species may constitute a first case report for a phototrophic biofilm. The results suggest an important role of bacteria in this type of biofilm and a complex microbial-interaction network.

Variations in biochemical and histological characteristics of WSSV infected green tiger shrimp Penaeus semisulcatus

White Spot Syndrome Virus causes viral disease in crustaceans and generates a significant burden in the developing nations. Biochemical and immunological assays were performed in WSSV infected Penaeus semisulcatus which were monitored in different salinity conditions. Continuous exposure of shrimps to WSSV showed a reduced life span, indicating the pathogenicity in Penaeidae species. Hence, this study is intended to investigate the protective antioxidant potential of the innate immune system consisting biochemical and morphological alterations. Penaeus semisulcatus challenged with white spot syndrome virus (5.5 × 104 copy number; WSSV) reared at different salinity 5, 15, 25 (control) and 35 g/L were examined after 0–120 h for immunological parameters such as total hemocyte count (THC), phenoloxidase (PO) and respiratory burst (RB) and alkaline and acid phosphatase activities. After 72 h, the WSSV injected P. semisulcatus tissues were histopathologically sectioned and stained. This study would be helpful to understand host–pathogen interaction and envisages the improvement of better management practices in shrimp aquaculture system.

A plant-based heat shock protein inducing compound modulates host–pathogen interactions between Artemia franciscana and Vibrio campbellii

Induction of heat shock proteins (e.g. Hsp70) has been considered as a potential disease control and health management strategies in aquaculture. Recently, the compound Tex-OE®, a patented extract from the skin of the prickly pear fruit, Opuntia ficus indica, was reported to enhance the production of Hsp70 in fish and shrimp tissues without any adverse effect, protecting the animals against various abiotic stressors. Most of the studies on this compound primarily focused on the positive effects at the level of the host while the effects on the microorganisms in the culture environment were often overlooked. In our study, we aimed at evaluating the effect of this compound on the interaction of the host brine shrimp Artemia franciscana with pathogenic Vibrio. Pretreatment of axenically-grown Artemia with Tex-OE® conferred significant protection against V. campbellii in a conventional rearing system. However, continuous exposure of axenniclly-grown Artemia to Tex-OE® in an open system negatively affected their survival. In vitro experiments provided unequivocal evidence that continuous exposure of Tex-OE® modulated the growth and virulence (such as hemolytic and caseinase activity) of V. campbellii. Pretreatment of Vibrio with the compound also increased their virulence in an Artemia challenge assay. Based on the overall results, it can be suggested that the compound Tex-OE® has the potential to be used as a disease control tool in (shrimp) aquaculture systems. However, the possibility that such kind of compounds also modulate the microbial activity cannot be ignored making the outcome dependent on the composition of the standing microbial community.

Use of formic acid to control vibriosis in shrimp aquaculture

Luminous vibriosis is a shrimp disease that causes major economic losses in shrimp industry as a result of massive shrimp kills due to bacterial infection caused by Vibrio species. Use of antibiotics to control Vibrio in shrimp aquaculture is not allowed in the United States and so it is necessary to develop an alternative pathogen control method for shrimp production. Short-chain fatty acids have been used as food preservatives for a long time. Organic acids are commonly added in feeds in animal production, such as chicken, pig, and cattle. In this study, growth inhibition effects of formic acid on five selected Vibrio species, namely Vibrio alginolyticus, Vibrio cholerae, Vibrio harveyi, Vibrio parahaemolyticus and Vibrio vulnificus were studied. The Vibrio bacteria were grown on both solid and liquid media using Muller-Hinton agar and alkaline peptone water, respectively, with various concentrations of formic acid. Bacterial growth was monitored in the liquid media using optical density method. The results showed significant inhibition of growth of all five Vibrio species by formic acid at low concentration. The effective concentration (EC50) values were calculated for all five Vibrio species, which were less than 0.039% of formic acid. The results are encouraging to supplement formic acid in the shrimp feed as a control mechanism to reduce Vibrio outbreak in shrimp aquaculture system.

A Nonluminescent and Highly Virulent Vibrio harveyi Strain Is Associated with “Bacterial White Tail Disease” of Litopenaeus vannamei Shrimp

Recurrent outbreaks of a disease in pond-cultured juvenile and subadult Litopenaeus vannamei shrimp in several districts in China remain an important problem in recent years. The disease was characterized by “white tail” and generally accompanied by mass mortalities. Based on data from the microscopical analyses, PCR detection and 16S rRNA sequencing, a new Vibrio harveyi strain (designated as strain HLB0905) was identified as the etiologic pathogen. The bacterial isolation and challenge tests demonstrated that the HLB0905 strain was nonluminescent but highly virulent. It could cause mass mortality in affected shrimp during a short time period with a low dose of infection. Meanwhile, the histopathological and electron microscopical analysis both showed that the HLB0905 strain could cause severe fiber cell damages and striated muscle necrosis by accumulating in the tail muscle of L. vannamei shrimp, which led the affected shrimp to exhibit white or opaque lesions in the tail. The typical sign was closely similar to that caused by infectious myonecrosis (IMN), white tail disease (WTD) or penaeid white tail disease (PWTD). To differentiate from such diseases as with a sign of “white tail” but of non-bacterial origin, the present disease was named as “bacterial white tail disease (BWTD)”. Present study revealed that, just like IMN and WTD, BWTD could also cause mass mortalities in pond-cultured shrimp. These results suggested that some bacterial strains are changing themselves from secondary to primary pathogens by enhancing their virulence in current shrimp aquaculture system.

Consumption and digestion of suspended microbes by juvenile Pacific white shrimp Litopenaeus vannamei

Microalgae hold a key role in the diet of the world's highest-valued seafood species, Pacific white shrimp Litopenaeus vannamei, but ingestion, digestion, and feeding mechanisms employed for consuming suspended microbes are not well studied. The goal of this work was to determine whether juvenile L. vannamei could consume and digest several microbes of varying sizes and structures in suspended monocultures. Diatoms Thalassiosira weissflogii and Amphiprora sp., eustigmatophyte Nannochloropsis salina, and cyanobacterium Synechococcus bacillarus were chosen based upon their common occurrence in intensive shrimp aquaculture systems. Juvenile 2 g L. vannamei, previously starved for 24 h, were individually stocked in aerated flasks containing axenic monocultures of T. weissflogii, Amphiprora sp., N. salina or S. bacillarus for 15, 30, 60, and 90 min. After designated immersion times, shrimp were dissected for collection of stomach and intestine content samples. Fluorometry was used to measure chlorophyll a (μg/g) within the stomach and intestine contents at each time increment. Counts of intact cells (cells/g) within the stomach and intestine contents were completed for shrimp that had been immersed for 60 min. Shrimp demonstrated a sweeping behavior of the third maxillipeds during submersion in some algal cultures, which led to examination through scanning electron microscope photography. Counts of intact cells and chlorophyll a levels in the stomach and intestine indicated that juvenile shrimp actively ingested and digested T. weissflogii and Amphiprora sp. from suspended monocultures. Diatom consumption and digestion were evident across all immersion times, with increasing levels of chlorophyll a in stomach samples up to but not significantly beyond 60 min, indicating that the experimental time period represented a continuous feeding period and spanned the gut passage time. Shrimp were able to ingest S. bacillarus and N. salina to a very limited degree, but there was no evidence of digestion of these cells. Examination under the scanning electron microscope revealed that the third maxillipeds have net-like setae which could potentially select for microorganism > 10 μm in size. Since this cell size reflected the difference between those cells consumed or not consumed in this study, we hypothesize that these appendages may be used by juvenile L. vannamei to filter food particles. These observations provide valuable insight regarding this shrimp's ability to capture and digest microalgae both within its natural environment and in aquaculture systems.

Quantitative role of shrimp fecal bacteria in organic matter fluxes in a recirculating shrimp aquaculture system

Microorganisms play integral roles in the cycling of carbon (C) and nitrogen (N) in recirculating aquaculture systems (RAS) for fish and shellfish production. We quantified the pathways of shrimp fecal bacterial activities and their role in C- and N-flux partitioning relevant to culturing Pacific white shrimp, Penaeus (Litopenaeus) vannamei, in RAS. Freshly produced feces from P. vannamei contained 0.6-7 × 10(10) bacteria g(-1) dry wt belonging to Bacteroidetes (7%), Alphaproteobacteria (4%), and, within the Gammaproteobacteria, almost exclusively to the genus Vibrio (61%). Because of partial disintegration of the feces (up to 27% within 12 h), the experimental seawater became inoculated with fecal bacteria. Bacteria grew rapidly in the feces and in the seawater, and exhibited high levels of aminopeptidase, chitinase, chitobiase, alkaline phosphatase, α- and β-glucosidase, and lipase activities. Moreover, fecal bacteria enriched the protein content of the feces within 12 h, potentially enriching the feces for the coprophagous shrimp. The bacterial turnover time was much faster in feces (1-10 h) than in mature RAS water (350 h). Thus, shrimp fecal bacteria not only inoculate RAS water but also contribute to bacterial abundance and productivity, and regulate system processes important for shrimp health.

Genetic heterogeneity of non-O1 and non-O139 Vibrio cholerae isolates from shrimp aquaculture system: a comparison of RS-, REP- and ERIC-PCR fingerprinting approaches

The genetic diversity of Vibrio cholerae isolated from black tiger shrimp (Penaeus monodon) aquaculture farms was determined using three PCR typing methods based on enterobacterial repetitive intergenic consensus (ERIC) sequences, ribosomal gene spacer (RS) sequence and repetitive extragenic palindromic (REP) sequences. Non-O1 and non-O139 V. cholerae isolates were obtained from shrimp pond water, pond sediment, shrimp head and shrimp muscle. RS-PCR yielded fewer bands than REP-PCR and ERIC-PCR. Higher similarity was observed in RS-PCR (75-100%) than in REP-PCR (60-95%) and ERIC-PCR (40-95%). A 100% similarity between V. cholerae isolates was only noticed in RS-PCR. The choleratoxigenic V. cholerae (non-O1 and non-O139) showed greater genetic similarity with ctx-negative V. cholerae than among ctx-positive V. cholerae. The greater similarity of ctx-positive V. cholerae with ctx-negative V. cholerae isolates indicates that the ctx-positive strains (non-O1 and non-O139) might have originated from autochthonous V. cholerae in the aquatic niche.

Evaluation in a Shrimp Aquaculture System Using Mangroves, Oysters, and Seaweed as Biofilters Based on the Concentrations of Nutrients and Chlorophyll a

Water from shrimp aquaculture ponds was circulated through a mangrove woodlot, oyster beds, and seaweed ponds in biofilter experiments designed to reduce environmental loads. Though the nutrient concentrations in the shrimp culture ponds were lower than those in the other ponds in many cases, the Chl. a concentration increased explosively in shrimp ponds and exceeded 160 μg/L. These results suggested that nutrients were used for the growth of phytoplankton. The Chl. a concentration was very low in the oyster pond, and it was suggested that oyster feed actively on phytoplankton. Ammonia was always lower in the seaweed ponds than in the oyster ponds, which suggested that seaweed took up ammonia. From the nitrogen budget, 27% of nitrogen in supplied feed was incorporated into shrimp, 32% was flowed to mangrove, oyster and seaweed ponds and removed with these biofilters, and 9% was added in the aquaculture system as dissolved inorganic and particulate nitrogen. Therefore, this aquaculture system using mangroves, oyster and seaweed as biofilters was thought to be effective to reduce the environmental load.

A brackishwater isolate of Pseudomonas PS-102, a potential antagonistic bacterium against pathogenic vibrios in penaeid and non-penaeid rearing systems

A Pseudomonas sp PS-102 recovered from Muttukkadu brackish water lagoon, situated south of Chennai, showed significant activity against a number of shrimp pathogenic vibrios. Out of the 112 isolates of bacterial pathogens comprising Vibrio harveyi, V. vulnificus, V. parahaemolyticus, V. alginolyticus, V. fluvialis, and Aeromonas spp, 73% were inhibited in vitro by the cell-free culture supernatant of Pseudomonas sp PS-102 isolate. The organism produced yellowish fluorescent pigment on King's B medium, hydrolysed starch and protein, and produced 36.4% siderophore units by CAS assay and 32 μM of catechol siderophores as estimated by Arnow's assay. The PS-102 isolate showed wide ranging environmental tolerance with, temperatures from 25 to 40 °C, pH from 6 to 8, salinity from 0 to 36 ppt, while the antagonistic activity peaked in cultures grown at 30 °C, pH 8.0 and at 5 ppt saline conditions. The antagonistic activity of the culture supernatant was evident even at 30% v / v dilution against V. harveyi. The preliminary studies on the nature of the antibacterial action indicated that the antagonistic principle as heat stable and resistant to proteolytic, lipolytic and amylolytic enzymes. Pseudomonas sp PS 102 was found to be safe to shrimp when PL-9 stage were challenged at 10 7 CFU ml − 1 and by intramuscular injection into of ∼5 g sub-adults shrimp at 10 5 to 10 8 CFU. Further, its safety in a mammalian system, tested by its pathogenicity to mice, was also determined and its LD 50 to BALB/c mice was found to be 10 9 CFU. The results of this study indicated that the organism Pseudomonas sp PS 102 could be employed as a potential probiont in shrimp and prawn aquaculture systems for management and control of bacterial infections.

Coastal Shrimp Aquaculture Systems in Southwestern Bangladesh

Coastal Shrimp Aquaculture Systems in Southwestern Bangladesh

Distribution of bacteria involved in nitrogen and sulphur cycles in shrimp culture systems of West Bengal, India

The bacteria involved in nitrogen and sulphur cycles and physicochemical characteristics of water and sediment in traditional, modified extensive and semi-intensive shrimp culture systems of West Bengal, India were monitored. The physicochemical parameters, except salinity and sediment pH, were observed to be well within the optimum levels recommended for shrimp culture. The levels of ammonia (NH 3; P≤0.05) and nitrite (NO 2 −; P<0.03) differed significantly among systems. The mean heterotroph counts were always close to or above 10 6/ml pond water and 10 6/g sediment. The counts of total heterotrophs and nitrate reducing bacteria (NRB) of the pond water of different culture systems differed significantly ( P<0.01). While the counts of nitrite oxidizing bacteria (NOB; P<0.001), nitrate reducing bacteria ( P<0.01) and sulphate reducing bacteria (SRB; P<0.03) in pond sediment of the three culture systems differed significantly. The mean counts of ammonia oxidizers increased with days of culture (DOC) in traditional and modified extensive systems, but they remained constant in semi-intensive pond sediment. The mean counts of nitrite oxidizers were generally high in water and sediment samples of modified extensive system. The mean sulphur oxidizing bacterial counts of pond water were higher in semi-intensive and modified extensive systems, which generally decreased with increasing DOC. The sulphate reducing bacterial counts of sediment increased with DOC in modified extensive and semi-intensive systems and vice versa in traditional system. The safe levels of ammonia, nitrite and nitrate recorded in the present study clearly showed that the recycling of nitrogen and sulphur is going on actively in shrimp aquaculture systems. The data on the ecology of bacteria involved in nutrient cycling will not only lead to better control of water quality but also application of right kind of bacteria or microbial products in shrimp aquaculture.

Risk of exceeding bioeconomic limit reference points in shrimp aquaculture systems

Designing intelligent management strategies for shrimp aquaculture systems require recognising the uncertainty and risks associated with different processes of aquaculture production. To account for natural variability and other sources of uncertainty, estimates of appropriate aquaculture bio‐economic indicators are needed to re‐evaluate periodically the production system and establish new reference points and corresponding management strategies. This paper concentrates on this aspect of the management process and presents a simple classification of indicators and reference points for aquaculture production systems. The uncertainty causing variability in the estimated values of bio‐economic parameters is incorporated through the use of Monte Carlo analysis to estimate the probability of exceeding limit reference points. To illustrate this process, the risks (i.e. probabilities of exceeding bioeconomic limit reference points) associated to alternative timing of harvesting decisions were estimated by randomly generating uncertain prices and natural mortalities with the appropriate probability density functions and corresponding variance. Alternative approaches to deal with risk and uncertainty in data limited management contexts are discussed.

A multiperiod programming evaluation of brackishwater shrimp aquaculture development in Indonesia 1989/1990–1998/1999

Brackishwater shrimp aquaculture was economically evaluated to determine the best mix of aquaculture enterprises in Indonesia. Data were compiled for three categories of brackishwater shrimp aquaculture systems: Extensive, semi-intensive, and intensive, as well as for different farm sizes, small-scale (2 ha), medium-scale (5 ha), large-scale (10 ha) and extra large-scale (30 ha). These data were used to simulate the enterprise combination for the shrimp-producing regions in Indonesia. Model results showed that small-scale and medium-scale semi-intensive systems were the best strategies for shrimp aquaculture development in Indonesia. Extensive systems entered in solution only if there were skilled labor constraints. Risk analysis revealed risk-expected net present income trade-offs and declining risk with declining expected net present income for all regions.