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Wet markets in low-and middle-income countries are often reported to have inadequate sanitation resulting in fecal contamination of sold produce. Consumption of contaminated wet market-sourced foods has been linked to individual illness and disease outbreaks. This pilot study, conducted in two major wet markets in Dhaka city, Bangladesh during a 4-month period in 2021 aimed to assess the occurrence and characteristics of Escherichia coli and nontyphoidal Salmonella spp. (NTS) from tilapia (Oreochromis niloticus) and shrimp (Penaeus monodon). Fifty-four individuals of each species were collected. The identity of the bacterial isolates was confirmed by PCR and their susceptibility toward 15 antimicrobials was tested by disk diffusion. The whole genome of 15 E. coli and nine Salmonella spp. were sequenced using Oxford Nanopore Technology. E. coli was present in 60–74% of tilapia muscle tissue and 41– 44% of shrimp muscle tissue. Salmonella spp. was found in skin (29%) and gills (26%) of tilapia, and occasionally in muscle and intestinal samples of shrimp. The E. coli had several Multilocus sequence typing and serotypes and limited antimicrobial resistance (AMR) determinants, such as point mutations on glpT and pmrB. One E. coli (BD17) from tilapia carried resistance genes for betalactams, quinolones, and tetracycline. All the E. coli belonged to commensal phylogroups B1 and A and showed no Shiga-toxin and other virulence genes, confirming their commensal non-pathogenic status. Among the Salmonella isolates, five belonged to Kentucky serovar and had similar AMR genes and phenotypic resistance patterns. Three strains of this serovar were ST198, often associated with human disease, carried the same resistance genes, and were genetically related to strains from the region. The two undetermined sequence types of S. Kentucky were distantly related and positioned in a separate phylogenetic clade. Two Brunei serovar isolates, one Augustenborg isolate, and one Hartford isolate showed different resistance profiles. This study revealed high fecal contamination levels in tilapia and shrimp sold at two main wet markets in Dhaka. Together with the occurrence of Salmonella spp., including S. Kentucky ST198, a well-known human pathogen, these results stress the need to improve hygienic practices and sanitation standards at markets to improve food safety and protect consumer health. [ABSTRACT FROM AUTHOR]

Microbial community inhabiting the intestine of the shrimp (Penaeus monodon) and their surrounding environments (e.g., water and sediment) is considered as a key contributing factor for the sustainable farming of shrimp. Indiscriminate application of antibiotics in aquaculture is a growing concern due to the emergence of antibiotic resistant bacteria (ARB), more specifically the antibiotic resistance genes (ARGs). The present study investigates the microbiome composition and 19 ARGs from four different shrimp farming systems; (i) cluster, (ii) extensive, (iii) semi-intensive, and (iv) improved extensive in the southwest coastal region of Bangladesh. In doing so, the study applied advanced 16S rRNA-based metagenomic sequencing to study the bacterial composition. Moreover, gene specific polymerase chain reaction (PCR) was employed to detect the ARGs in shrimp, water, and sediments of different farming systems. In the current study, bacteria from the phylum Proteobacteria and Firmicutes were predominant among the samples (n = 12) collected from the different farming systems followed by Actinobacteria, Bacteroidetes, and Cyanobacteria. Firmicutes was the predominant phylum in the gut of shrimp cultured in the cluster (relative abundance 53.33%) and semi-intensive (relative abundance 59.2%) culture systems. Results indicated that the bacterial community structure was significantly (p < 0.05) distinct among gut, sediment, and water samples as well as the farming systems. The shared operational taxonomic unit (OTU) in the sediment sample (16,495) was nearly double than the gut (7,931) and water (8,513) bacterial communities. The improved extensive farming system showed 1,289 (11.05%) shared OTUs among gut, sediment, and water followed by semi-intensive (6.87%), cluster (6.27%), and extensive (5.46%) farming system. Among the tested ARGs, sul1, cat, gyrA(C), tetA, tetC, tetX, ere(A), vanR, and dfrA1 were predominant in water and sediment samples. Semi-intensive farming system had the highest prevalence of ARGs (21.05%) while the lowest prevalence was found in extensive (5.26%) farming system. Overall, the study provides a comprehensive scenario of bacterial composition and growing emergence of ARGs in shrimp farming of Bangladesh. Therefore, the production strategy must focus on the alternatives of antibiotic for shaping the shrimp cultivation technique more sustainable. [ABSTRACT FROM AUTHOR]

Commercial cultivation of Litopenaeus vannamei, popularly known as white leg shrimp or vannamei shrimp, has significantly boosted the global shrimp industry over the last 10 years. Higher yield potential, increasing market demand, shorter cultivation cycles and less vulnerability to diseases prompted the major shrimp-producing countries to introduce Litopenaeus vannamei. However, as of today, no academic sources are available supporting the commercial farming of Litopenaeus vannamei in Bangladesh—an important actor in the global shrimp industry. In recent years, Bangladesh's shrimp industry has already started to lose global competitiveness due to the deficient production (0.0347 tonne/ha) of traditionally cultivated black tiger shrimp (Penaeus monodon), which is highly susceptible to white sport syndrome diseases. This opinion article aims to spark a policy stimulation justifying the immediate policy measures to introduce high-yielding Litopenaeus vannamei species to revitalize the declining shrimp industry in Bangladesh. [ABSTRACT FROM AUTHOR]

The black tiger shrimp, Penaeus monodon, is the most economically important penaeid shrimp in Bangladesh for both culture and capture fishery. The culture of these penaeid shrimps is always risky due to different diseases and environmental stressors. This study aimed to assess the relative expression of the Penaeus monodon Rab7 gene in the post larvae (PL) of the P. monodon cultured under different salinity conditions. We challenged the PL of the P. monodon in aquariums with two different salinity and dissolved oxygen conditions during a 7-day test. The relative expression of Rab7 was upregulated during the experimental period of 36 hours. Average differences in the relative expression of Rab7 were 0.3-folds and 0.5-folds, and 0.4-folds and 0.6-folds after 18 and 36 hours of rearing in 2 and 54 ppt salinity treated shrimp PL, respectively, when ß-actin was used as an internal control. On the other hand, when elongation factor 1 alpha (EF1a) was used for normalization, the average relative expression of Rab7's fold differences were 0.2-folds and 0.5-folds, and 0.3-folds and 0.6-folds after 18 and 36 hours of rearing in 2 and 54 ppt salinity treated shrimp PL, respectively. Therefore, our results suggested that the relative expression of the Rab7 was positively correlated with an increased level of salinity and challenge duration. The significant increase in the expression level of Rab7 in the PL of P. monodon exposed to high salinity stress (54 ppt) conditions indicated its functional role in osmotic stress in shrimps. However, further studies are necessary to elucidate the mechanisms of how Rab7 is upregulated in shrimp cells after applying different levels of salinity using a larger sample group. [ABSTRACT FROM AUTHOR]

Some Vibrio species can cause food-borne diseases in humans, including cholera, vomiting, septicemia, and gastroenteritis, which are associated with the consumption of contaminated seafood products. The study was conducted to detect antimicrobial-resistant Vibrio species in shrimp and shrimp environments in Bangladesh. Samples of shrimp (n = 50), water (n = 50), and mud (n = 50) were collected aseptically from 50 different shrimp culture ponds in the Khulna region of Bangladesh. Identification of Vibrio species was based on cultural and staining characteristics, biochemical tests, and polymerase chain reaction (PCR). Antimicrobial resistance profiles were determined using a disk diffusion assay. By PCR, Vibrio isolates were found in 34% (95% CI: 26.9%–41.9%) of the samples, of which the detection rate was significantly higher in shrimp (54%), compared to mud (26%) and water (22%). Moreover, V. cholerae, V. parahaemolyticus, and V. alginolyticus were detected in 24.7%, 15.3%, and 4% of the samples, respectively. Among them, the detection rate of V. cholerae and V. alginolyticus was significantly higher in shrimp samples than in other samples. V. parahaemolyticus was also higher in the shrimp samples, but the difference was not statistically significant. Vibrio isolates showed high to moderate resistance (92.2%–15.7%) to ampicillin, amikacin, cefotaxime, tetracycline, ceftazidime, gentamicin, nalidixic acid, levofloxacin, and ciprofloxacin, and low resistance (3.9%) to imipenem, meropenem, chloramphenicol, and trimethoprim-sulfamethoxazole. Interestingly, 52.9% of the isolates were multidrug resistant, and the multiple antibiotic resistance index was up to 1.0. To our knowledge, this is the first study in Bangladesh detecting these three Vibrio species (V. parahaemolyticus, V. alginolyticus, and V. cholerae) from shrimp and shrimp environments by molecular approach in the same study. These findings reveal the alarmingly high occurrence of antimicrobial-resistant Vibrio species in shrimp and shrimp environments, which should be of concern to both the shrimp industry and public health management. [ABSTRACT FROM AUTHOR]

This study used a random selection of 150 extensive shrimp farms in three areas in Bangladesh (Paikgacha, Dacope, and Chokoria) and questionnaires to examine the quality, hygiene, and sanitation practices that farmers used to satisfy national and international concerns. The majority (95.67%) of farmers in all three sites did not examine the quality of the hatchery-bred post larvae (PL) and felt that the hatchery used chemicals or antibiotics in producing PL and supplied under-aged PL (below PL15), resulting in significant mortality when released onto the farms. The majority of farmers (83.3%) performed a visual inspection, examining shrimp size, weight, and disease symptoms before harvesting. Farmers in Chokoria were better aware of the need of inspecting quality features (growth, disease, weight, and shell) before harvesting than farmers in Dacope and Paikgacha. Farmers frequently neglected the icing of caught shrimp at the request of the buyer. To reduce losses, they took action when collected shrimp exhibited indicators of low quality, such as the presence of spots (43.3%), fragile shells (37.3%), and accidental debris (88.7%). Shrimp producers also enhanced their quality standards by using 100% plastic crates to transport shrimp and by improving working surfaces (92%) to wash, sort, and sell the collected shrimp, and building sanitary restrooms (100%) at a safe distance from the farms. Farmers believed that new laws had forced them to enhance safety, hygiene, and sanitation standards in order to decrease the poor quality image of Bangladesh shrimp held by international buyers, despite higher operating expenses and lower profitability. Highlights: • Black tiger shrimp (Penaeus monodon) is the majority farmed species, which is cultivated extensively across the coastal regions of Bangladesh. • This study assessed how shrimp farmers evaluated the quality of input supplies during the production and post-harvest stages. • Data from 150 shrimp farms in three different locations were collected using a questionnaire and analysed in Microsoft Excel and Statistical Package for Social Science software. • Pesticides or growth hormones were not used by farmers. Shrimp producers improved their quality standards by transporting shrimp in plastic crates, upgrading working surfaces for washing, sorting, and selling harvested shrimp. • Farmers were dissatisfied with the quality of hatchery PL. Farmers also lacked scientific knowledge on evaluating PL and shrimp quality on their farms, placing stock at risk of disease. • After harvesting, shrimp were exposed to ambient temperatures, and farmers frequently refrained from icing them at the request of the next purchasers such as forias or depots. The latter saw icing as increasing shrimp weight and hence purchase prices. [ABSTRACT FROM AUTHOR]

Shrimp is one of the major export products in South Asian countries and also an eminent source of nutrition for humans. Hence, any negative effect of this industry may affect not only the country's economy but also human health. Therefore, in this study, we aimed to assess heavy metal contamination and associated human health risks in cultured shrimp (Penaeus monodon) and aquaculture sludge collected from three shrimp farms of the Cox's Bazar district, Bangladesh. The results showed that among the eight metals studied, Pb (17.75 ± 1.5 mg/kg) and Cu (9.43 ± 2.8 mg/kg) levels in all shrimp samples were higher than the recommended limit, whereas the concentrations of Cd (0.09 ± 0.03 mg/kg), Mn (4.83 ± 2.2 mg/kg), As (0.04 ± 0.02 mg/kg), Hg (0.02 ± 0.006 mg/kg), Zn (18.89 ± 2.9 mg/kg) and Cr (0.69 ± 0.6 mg/kg) were within the permissible level. The concentrations of Mn (1043.37 ± 59.8 mg/kg), Cr (30.38 ± 2.1 mg/kg), Zn (74.72 ± 1.13 mg/kg) and Cu (31.14 ± 1.4 mg/kg) in the sludge of all farms were higher than the recommended limit, whereas the concentrations of Pb (20.23 ± 1.9 mg/kg), Cd (0.09 ± 0.2 mg/kg), As (0.44 ± 0.34 mg/kg) and Hg (0.08 ± 0.02 mg/kg) in all sludge samples were lower than the threshold limits. However, the estimated daily intake (EDI), targeted hazard quotient (THQ) and hazard index (HI) assessed for potential human health risk implications suggested that Pb and Cr may pose non-carcinogenic health effects, although carcinogenic risks (CR) values were acceptable for consumers. However, the pollution load index (PLI) of the studied area was below 1, which indicates low deterioration of the area. Geoaccumulation index (Igeo) and contamination factor (CF) analyses revealed that study area is unpolluted and sludge is enriched with metals in the following order: Mn > Zn > Cu > Cr > Cd > Hg > Pb > As. [ABSTRACT FROM AUTHOR]

Microplastics (MPs) were analyzed in seven shrimp species Tiger shrimp (Penaeus monodon), Red tiger shrimp (Caridina cantonensis), Indian shrimp (Penaeus indicus), Red shrimp (Metapenaeus dobsoni), White shrimp (Penaeus merguiensis), Brown shrimp (Metapenaeus monoceros), and Roshna shrimp (Palaemon styliferus) collected from the Bay of Bengal. The abundance and characteristics of MPs were assessed in the gastrointestinal tract (GIT), which certainly translocated to the muscle of shrimp species. The highest MP abundance was found in C. cantonensis with 7.2 items/individual (25.3 items/g in the GIT and 6.3 items/g in muscle). The prominent types of MPs in shrimp samples were fibers (30 %) and fragments (29 %). The ingestion rate of MPs of black and transparent color was comparatively higher, with 64 % of the ingested MPs were < 100 μm. The primary polymer types detected based on Fourier Transform Infrared (FTIR) analysis were Low-Density Polyethylene (LDPE), High-Density Polyethylene (HDPE), Polymethyl Methacrylate (PMMA), Polyvinyl Chloride (PVC), Polypropylene (PP), and Ethylene Vinyl Acetate (EVA). Results from Scanning Electron Microscopy (SEM) showed rough surface textures and adhered particles on the MPs isolated from shrimps. The margin of exposure for females was 71.42, and for males, it was 80.64, indicating that women in Bangladesh are more likely to be exposed to MPs and face a higher risk than men. Sensitivity analysis revealed that MPs particle size was the most sensitive parameter. These findings provide a comprehensive understanding of MP ingestion, human exposure, and contamination in shrimps of Bangladesh, which can help future monitoring efforts. • Caridina cantonensis exhibited highest microplastic level with 7.2 items/individual. • Microplastics in shrimps were mostly fibers, <100 μm in size and transparent in color. • The identified microplastic polymers included HDPE, LDPE, PVC, PP, PMMA, and EVA. • Margin of exposure for females was 71.42, indicating higher exposure and risk. [ABSTRACT FROM AUTHOR]

Black Tiger Shrimp (Penaeus monodon) is one of the leading export commodities in Bangladesh. The industry, however, is frequently beset with quality deterioration and microbial diseases owing to various reasons. Here, we analyzed the sensory and nutritional qualities of shrimp, the total bacterial count, and molecular identification of pathogenic bacteria in samples collected from different supply chain actors (SCA), including the gher (farms), depots, wholesalers, retailers, and the processing industry in Khulna, Bangladesh. While the Sensory Quality Indices (SQI) of shrimps collected from farms, depots, and processing plants were found 'excellent and highly acceptable', the rating for wholesale and retail markets were 'good and acceptable'. Nutritionally, higher protein (21.59%), lipid (1.47%), and ash (1.97%) contents were found in shrimps collected from farms than that of other SCAs. Heterotrophic bacterial count (cfu/g) differed in various SCAs: farms 3.75±0.31 (×106), depots 3.95±0.92 (×106), wholesale markets 5.03±0.35 (×106), retail markets 4.82±0.40 (×106), and the processing industry 3.78±0.25 (×106). The presence of Ralstonia spp and Pseudomonas spp, confirmed by 16S rDNA sequencing were found in different SCAs. Overall, the quality of shrimp appeared better in farms than that of other SCAs, indicating that a lack of proper hygiene, sanitation, and post-harvest handling practices could be the likely impediments for quality deterioration. [ABSTRACT FROM AUTHOR]

The aim was to assess the efficacy of prophylactic health products (PHPs) on shrimp (Penaeus monodon) post larvae (PL) during the nursery phase. This included five treatments: infeed probiotic (F_PRO), water probiotic (W_PRO), a combination of water and infeed probiotic (FW_SYN), biofloc, a combination of biofloc and infeed probiotic (F_PRO&biofloc), and a no‐treatment control, five replicates each. Each tank was filled with 450 L water and stocked with 700 PL15, weight 0.008 ± 0.00 g at a density of 1.56 PL/L, reared for 27 days. There were no significant differences in water temperature, dissolved oxygen, alkalinity, and total ammonia nitrogen among treatments and control. pH and nitrite were lower in biofloc and F_PRO&biofloc compared to other treatments. The final body weight, weight gain, specific growth rate and food conversion ratio were significantly higher (p ≤.05) in F_PRO&biofloc compared to other treatments and control. A salinity stress test showed a significantly higher survival rate in F_PRO&biofloc followed by biofloc than other treatments and control. Our study indicated that rearing shrimp in biofloc alone or combined with infeed probiotic might increase growth and resistance to environmental stressors. Further on‐farm trials are required to confirm the efficacy of the PHPs. [ABSTRACT FROM AUTHOR]

Vibriosis caused by luminous Vibrio species is one of the biggest challenges to shrimp industry in Bangladesh. This study aimed to characterize whole microbial communities from Vibrio‐infected black tiger shrimp (Penaeus monodon) using 16S rRNA‐based amplicon sequencing. A total of 36 disease‐free and infected shrimp were collected from six different hatcheries in Bagerhat, Bangladesh. A final pool of 12 samples (n = 6) was created by homogenization of the hepatopancreas samples from three shrimps collected from each hatchery for the same group. The amplicon sequencing data revealed significant (p <.05) decrease of alpha diversity measurements and subsequent effects (p <.05) on the hepatopancreas microbiota in the infected group, compared to control shrimp. Proteobateria and Aeromonas were the most dominant bacteria at phylum and genus level in both groups and identified as core microbiota in the community. Two bacterial groups at phyla level and eight at genus level were found associated with the alteration of hepatopancreas microbial communities and associated gene functions in vibriosis‐infected shrimp, revealed by differential abundance and KEGG pathway analysis. The overwhelming abundance of Citroibacter, Shewanella and Candidatus lineages in vibriosis‐infected shrimp needs further investigations. [ABSTRACT FROM AUTHOR]

Vibrio parahaemolyticus is a major foodborne pathogen responsible for significant economic losses in aquaculture and a threat to human health. Here, we explored the incidence, virulence potential, and diversity of V. parahaemolyticus isolates from aquaculture farms in Bangladesh. We examined a total of 216 water, sediment, Oreochromis niloticus (tilapia), Labeo rohita (rui), and Penaeus monodon (shrimp) samples from the aquaculture system where 60.2% (130/216) samples were positive for V. parahaemolyticus. Furthermore, we identified 323 V. parahaemolyticus strains from contaminated samples, 17 of which were found positive for trh , a virulence gene. Four isolates out of the 17 obtained were able to accumulate fluid in the rabbit ileal loop assay. The correlation between the contamination of V. parahaemolyticus and environmental factors was determined by Pearson correlation. The temperature and salinity were significantly correlated (positive) with the incidence of V. parahaemolyticus. Most of the pathogenic isolates (94.1%) were found resistant to ampicillin and amoxicillin. O8: KUT was the predominant serotype of the potentially pathogenic isolates. ERIC-PCR reveals genetic variation and relatedness among the pathogenic isolates. Therefore, this region-specific study establishes the incidence of potential infection with V. parahaemolyticus from the consumption of tilapia, rui, and shrimp raised in farms in Satkhira, Bangladesh, and the basis for developing strategies to reduce the risk for diseases and economic burden. [ABSTRACT FROM AUTHOR]

Acute hepatopancreatic necrosis disease (AHPND) is an emerging shrimp (Penaeus monodon) disease caused by Vibrio parahaemolyticus (VP) since 2013 in Bangladesh. The aim of this work was to evaluate a PCR and RT-PCR techniques as rapid methods for detecting V. parahaemolyticus AHPND-positive P. monodon using genetic markers. Healthy and diseased shrimp (P. monodon) samples were collected from three monitoring stations. The samples were enriched in TCBS plates and DNA extraction from the cultured bacteria. DNA quantifications, PCR amplification, RT-PCR, and gene sequencing were done for the detection of V. parahaemolyticus AHPND-positive P. monodon. The sequence of PCR amplicons showed 100% identity and significant alignment with V. parahaemolyticus. The primers used provided high specificity for V. parahaemolyticus in PCR detection compared with another Vibrio species. In the PCR, amplification resulted positive amplicons, whereas, non-AHPND isolates showed no amplicons. Neighbor-joining methods indicated that all genes evolved from a common ancestor and clades have different traits with very low genetic distance and low variability. The pairwise alignment scores of atpA, tox, blaCARB, 16S rRNA, and pirA genes were 100.0, 98.90, 98.89, 95.53, and 41.42, respectively. The RT-qPCR exposed variable expression levels for all genes in the AHPND-positive strain. Homology analysis and distance matrix exhibited all genes to have the lowest similarity and most divergence, offering the highest specificity. In this study, the expression and variability of target genes confirmed the presence of V. parahaemolyticus in all sampling sites. The results suggested that PCR amplification, RT-qPCR, and gene sequencing can be used for the rapid detection of V. parahaemolyticus in AHPND-positive P. monodon that may lead to subsequent prevention and treatment research in the future for managing this disease. [ABSTRACT FROM AUTHOR]

Stocking specific-pathogen-free (SPF) shrimp postlarvae (PL) has been reported to have much potential to enhance production by notably reducing the infection-driven mortality. In terms of SPF PL production in Bangladesh, except white spot syndrome virus (WSSV), several potential viruses such as hypodermal and hematopoietic necrosis virus (IHHNV), monodon baculovirus (MBV), hepatopancreatic parvovirus (HPV), and yellow head virus (YHV) which may synergistically cause mortality are ignored. Therefore, this study aimed to investigate the viral contamination in hatchery-brood-shrimps in Bangladesh as the broods horizontally and/or vertically transfer the viruses to their offspring. Five randomly selected representative hatcheries were investigated over 3 months (January to March) to know the status of viral contamination. Broods in all the hatcheries were found to be contaminated with WSSV, IHHNV, MBV, HPV, and YHV. The results showed that the prevalence of WSSV, MBV, HPV, and YHV did not significantly differ between hatcheries. The highest (72%) and the lowest (30%) prevalence of MBV and WSSV, respectively, were recorded in January. In February, the highest (81%) and the lowest (28%) prevalence were found in MBV and HPV, respectively, where the highest and the lowest prevalence were 88% and 40% for IHHNV and HPV, respectively, in March. The prevalence of IHHNV and MBV were not significantly different. The relative prevalence of WSSV, HPV, and YHV were significantly low compared with that of IHHNV and MBV. Notably, increasing water temperature from January (22 ± 0.71 °C) to March (27 ± 1 °C) increased the prevalence of all the viruses and subsequently the extremity of infection. The contamination in broods forwarding to the production of multiple-virus-contaminated PL is considered as an obstacle to higher production of shrimp at farm level in Bangladesh. Hence, the present study suggests focusing on the deleterious-virus-free shrimp broods in commercial shrimp hatcheries in Bangladesh. [ABSTRACT FROM AUTHOR]

Shrimp aquaculture industry comprises 15 % of the internationally traded seafood products targeted for human consumption. Diseases of shrimp have caused severe economic losses to the aquaculture industry. Among pathogenic bacteria, several Vibrio species known as shrimp pathogens are also human pathogens. This study was conducted to identify the incidence of diversified Vibrio species in the shrimp Penaeus monodon Fabricius, 1798 farms in Bangladesh. Different Vibrio selective media were used for primary isolation and 16S rRNA gene amplicons were sequenced, followed by phylogenetic analysis. The Vibrio strains were also tested against twelve antibiotics. Two strains V32 and V38 showed 99.93 % similarity with Vibrio azureus whereas V9 and V33 showed 100 % identity with Vibrio fluvialis. Comparison of 16S rRNA gene sequence of V37 with sequences from GenBank identified the strain as Vibrio xuii. The phylogenetic tree indicates that V24, V26, V34 and V35 are closely related with Vibrio parahaemolyticus. The strains V28 and V31 were identified as Vibrio vulnificus. One strain of Vibrio cholerae was also identified. Moreover, V22 was identified as Photobacterium damselae subsp. damselae, and V25 as Aeromonas hydrophila. Twelve strains of Vibrio were resistant to amoxycillin, whereas all 16 bacterial isolates showed sensitivity to nitrofurantoin, sulphamethoxazole, chloramphenicol, ciprofloxacin and tetracycline. Multidrug resistance was observed in three isolates viz. V28, V32 and V35 which were identified as V. vulnificus, V. azureus and V. parahaemolyticus, respectively having MAR index of 0.25. These findings might have potential applications in controlling shrimp and human pathogenic vibrios in the farming regions. [ABSTRACT FROM AUTHOR]

The length-weight relationships (LWRs) were studied for 616 individuals covering 10 families of 12 fish species (i.e., Planiliza subviridis, Opsarius barna, Nandus nandus, Clarias batrachus, Odontamblyopus rubicundus, Taenioides cirratus, Anabas testudineus, Mystus gulio, Mystus tengara, Oreochromis mossambicus, Puntius sophore and Hyporhamphus limbatus) and 3 shellfish species (i.e., Penaeus monodon, Fenneropenaeus indicus, Metapenaeus brevicornis). Total length (cm) and body weight (g) were measured for each individual. The allometric co-efficient, b values of studied species ranged between 2.03 (M. gulio) to 3.27 (O. mossambicus) and were highly significant (P < 0.001) for all species. Our results contribute to updating the online database (FishBase or SeaLifeBase) of respective fish and shellfish species. [ABSTRACT FROM AUTHOR]

Culture of shrimp, mainly Penaeus monodon, makes an important contribution to Bangladesh's aquaculture industry. Shrimp hatcheries are the foundation on which the shrimp industry is built. Hatchery performance and management therefore has extremely important implications for the long-term viability of the entire shrimp sector, especially given its vulnerability to diseases such as white spot syndrome virus ( WSSV). This article provides a review of the history of shrimp hatchery development in Bangladesh and an overview of the current status of the shrimp hatchery sector and the challenges it faces. This article also provides a unique historical analysis of shrimp broodstock performance and rates of WSSV infection using data collected from hatcheries between 2007 and 2013. This reveals sharp declines in broodstock quality and performance over time, and high rates of WSSV infection, with potential major implications for the future sustainability of the sector. [ABSTRACT FROM AUTHOR]

Abstract: A comparative study to assess length, weight, fecundity, hatching rate and White Spot Syndrome Virus (WSSV) prevalence in black tiger shrimp (Penaeus monodon) broods collected from shallow and deep water zones of the Bay of Bengal was carried out in Cox's Bazar, Bangladesh. Average size and reproductive performance of broods from the deep zone were significantly higher than those of broods caught from the shallow zone. The incidence of WSSV infection in shallow zone broods was much higher than that in deep zone broods. The association between depth zone and WSSV infection is independent of brood size. WSSV infection is negatively associated with hatching rate, irrespective of location. Exclusive use of tiger shrimp broods collected from the deep zone could reduce vertical transmission of WSSV by 46% without additional management measures. A variety of economic, social and ecological factors make this potential solution unworkable however. A better alternative could be to promote the use of domesticated P. monodon broods. [Copyright &y& Elsevier]

Mangrove leaf litter is a potential source of nutrients for shrimp post larvae. To introduce mangrove trees in shrimp farms it is necessary to identify the combination of trees which is most beneficial for shrimp. The present study evaluated the effects of mixed leaf litter of four mangrove species (Avicennia officinalis (Ao), Sonneratia apetala (Sa), S. caseolaris (Sc) and Heritiera fomes (Hf) on shrimp post larvae performance and water and soil quality. Leaf litter with and without supplemental feed was applied to shrimp culture tanks according to a 4 × 2 factorial design and followed by testing a subset of treatments in mesocosm pond conditions. Shrimp post larvae of 15-days old (PL 15) with an average weight of 0.01 g were used for both experiments, each with a 4-week duration without water exchange. Under controlled conditions in the tanks, leaf litter and feed resulted in 22 to 32% higher weight gain of PL shrimp than combined weight gain realized when receiving only leaf litter or only feed, indicating synergism. Based on this, the pond experiment was designed with combined application of leaf litter and feed. The pond experiment resulted in higher shrimp weight gain than realized in the tanks. In tanks, the highest average individual weight gain of PL was observed for the leaf litter mixture SaAoHf (0.23 g)followed by SaScHf (0.21 g), ScAoHf (0.21 g) andSaScAoHf (0.20 g). Paralleling the results of the tank experiment, SaAoHf leaf litter also gave the highest average individual weight gain (1.2 g) of PL shrimpin the ponds but other leaf litter treatments followed by SaScAoHf (0.95 g), ScAoHf (0.84 g) and SaScHf (0.69 g) leaf litter. The different mixtures of mangrove leaf litter also resulted in significant differences in biological oxygen demand (BOD 5), phytoplankton and zooplankton concentrations in pond water and organic carbon in soil. Both phytoplankton (P < 0.01, Pearson correlation r = 0.910)and zooplankton (P < 0.05, r = 0.535) abundance was positively correlated to shrimp weight gain. The low feed conversion ratio (FCR) in the treatments combining leaf litter and supplemental feed as compared to treatments using only feed indicated extra food benefits for shrimp PL from decomposing leaf litter. Overall, mixed mangrove leaf litter had a positive effect on shrimp performance and this effect was highest for SaAoHf leaf litter. • Mixed mangrove leaf litter combined with feed creates synergy in shrimp culture ponds. • Shrimp post larvae grow better on mangrove leaf litter in mesocosm ponds than in tanks. • The contribution of mangrove leaf litter to shrimp production depends on the mix of tree species. • Shrimp production correlates positively with phytoplankton and zooplankton in mesocosm ponds. [ABSTRACT FROM AUTHOR]

The two economically important shrimp species in Bangladesh are the tiger shrimp, Penaeus monodon, and the brown shrimp, Metapenaeus monoceros. However, a continuous decline in the landing of these species from the industrial trawling made it critical to assess their stock biomass status to explore their response to the present degree of removal. Given the minimum data requirement and robustness, this study employed the depletion-based stock reduction analysis (DB-SRA) to assess these fisheries rigorously. For the industrial fishing zone (beyond the 40 m depth in the EEZ of Bangladesh), the estimated historic mean carrying capacity (K) was 5015 metric tons for the Penaeus monodon and 35,871 metric tons for Metapenaeus monoceros. The estimated overfishing limits (OFL), which were much smaller than the reported catches throughout the time series, indicate the overfishing status of these fisheries. As a result, the estimated biomass for the reference year (B2020) for both species was lower than BMSY, indicating that these fisheries are not producing MSY. Therefore, for the rebuilding and sustainable management of these stocks, this study recommended a catch limit of 100 metric tons for P. monodon and 750 metric tons for M. monoceros for the next ten years from biomass projections. [ABSTRACT FROM AUTHOR]

White Spot Syndrome Virus (WSSV) has emerged as one of the most prevalent and lethal viruses globally and infects both shrimps and crabs in the aquatic environment. This study aimed to investigate the occurrence of WSSV in different ghers of Bangladesh and the virulence of the circulating phylotypes. We collected 360 shrimp (Penaeus monodon) and 120 crab (Scylla sp.) samples from the south-east (Cox's Bazar) and south-west (Satkhira) coastal regions of Bangladesh. The VP28 gene-specific PCR assays and sequencing revealed statistically significant (p < 0.05, Kruskal–Wallis test) differences in the prevalence of WSSV in shrimps and crabs between the study areas (Cox's Bazar and Satkhira) and over the study periods (2017–2019). The mean Log load of WSSV varied from 8.40 (Cox's Bazar) to 10.48 (Satkhira) per gram of tissue. The mean values for salinity, dissolved oxygen, temperature and pH were 14.71 ± 0.76 ppt, 3.7 ± 0.1 ppm, 34.11 ± 0.38 °C and 8.23 ± 0.38, respectively, in the WSSV-positive ghers. The VP28 gene-based phylogenetic analysis showed an amino-acid substitution (E→G) at the 167th position in the isolates from Cox's Bazar (referred to as phylotype BD2) compared to the globally circulating one (BD1). Shrimp PL artificially challenged with BD1 and BD2 phylotypes with filtrates of tissue containing 0.423 × 109 copies of WSSV per mL resulted in a median LT50 value of 73 h and 75 h, respectively. The in vivo trial showed higher mean Log WSSV copies (6.47 ± 2.07 per mg tissue) in BD1-challenged shrimp PL compared to BD2 (4.75 ± 0.35 per mg tissue). Crabs infected with BD1 and BD2 showed 100% mortality within 48 h and 62 h of challenge, respectively, with mean Log WSSV copies of 12.06 ± 0.48 and 9.95 ± 0.37 per gram tissue, respectively. Moreover, shrimp antimicrobial peptides (AMPs), penaeidin and lysozyme expression were lower in the BD1-challenged group compared to BD2 challenged shrimps. These results collectively demonstrated that relative virulence properties of WSSV based on mortality rate, viral load and expression of host immune genes in artificially infected shrimp PL could be affected by single aa substitution in VP28. [ABSTRACT FROM AUTHOR]

Currently, antibiotics are widely used in shrimp hatcheries to control bacterial infections. Appearance of antibiotic resistant pathogens and restriction on the use of antibiotics have led to the development of alternatives to antibiotics in hatchery systems. In light of this, an attempt was undertaken to investigate the effects of probiotics on the larval rearing of Penaeus monodon, compared with the control tanks (without probiotics). The results showed that several issues significantly improved with administering probiotics in the experimental tanks compared with the tanks without probiotics. For example, the concentration of ammonia was estimated to be 1.25 mg/L which was less than a half of what was measured in the control tanks. The size variation was observed more in the control tanks than in the experimental tanks. Moreover, the muscle gut ratio of PL15 was about 85 to 92% in the probiotic treated tank and 70 to 80% in the control tank during the eight cycles of production. The fouling organisms were more in the control tank compared to the experimental tanks. The average length of PL15 was maximum when reared in the experimental tanks compared to the control tanks. The final survival rate of PL15 from the control and experimental tank was 35 and 52%, respectively. The present investigation indicated that probiotics played an important role in the growth, survival and health status of P. monodon larvae. [ABSTRACT FROM AUTHOR]

Abstract: Black tiger shrimp (Penaeus monodon) cultivation in gher (modified rice fields or ponds located beside canals or rivers) is widespread in southwestern Bangladesh. Shrimp farming plays an important role in the economy of the country, as it earns foreign exchange and provides employment opportunities. Organic shrimp aquaculture has emerged as an alternative farming enterprise for farmers, especially in the southwestern districts of Bangladesh. In this study, an asset-based conceptual framework known as the sustainable livelihoods approach (SLA) is applied to evaluate the impact of organic shrimp farming on livelihood. Data were collected in 2009 in the Kaligonj and Shyamnagar subdistricts through questionnaire interviews, transect walks, and focus group discussions with 144 organic shrimp farmers. Shrimp farming experience and size of gher have been found to influence the income from organic shrimp aquaculture. In this region, all farmers are highly vulnerable to natural phenomena like cyclones, floods, diseases, as well as contamination of saline water from untreated water sources, and market and price fluctuations that directly hinder the economic growth. The study concludes that more options for shaping livelihoods can be achieved if the farmers’ capacity in coping with uncertain phenomena is increased. The adoption of organic shrimp farming has increased farmers’ assets and has mitigated their vulnerability in ways that make livelihoods sustainable. [Copyright &y& Elsevier]

Bangladesh enters into international shrimp market in early 1970s but now it takes second places in the source of foreign currency earning. Now this sector facing a serious problem with a disease named White Spot Syndrome Virus which causes 100% mortality in the shrimp farm within two weeks. In Bangladesh, outbreak of White Spot Syndrome Virus has been a serious problem since 1995. In the present study, it was observed the present situation of White Spot Syndrome Virus prevalence in wild tiger shrimp brood, nauplii and post-larvae in Bangladesh. The result shows that prevalence of White Spot Syndrome Virus in wild tiger shrimp brood was in decreasing trend, but post-larvae during the study period. White Spot Syndrome Virus prevalence in tiger shrimp brood, nauplii and post larvae was found highest in the month of March and April and after that it was decreasing up to July and again increases in the month of August. [ABSTRACT FROM AUTHOR]

The Indian Sundarbans, a diversified coastal wetland on the southern fringe of the State of West Bengal, harbors a luxuriant biodiversity and acts as a potential refuge of living marine resources. Girdled with thick mangrove foliage, this estuarine delta system offers an excellent nursery ground for most of the brackishwater finfish and shellfish. Since supply of hatchery-produced tiger prawn seed (Penaeus monodon) is highly inadequate in West Bengal, the aquaculture farms of this region largely depend on the supply from natural resources. Being motivated by a regular cash income, the majority of coastal people from Sundarbans have adopted prawn seed collection as their profession almost throughout the year as an important source of earning. The users are neither trained nor guided at any stage from collection to marketing and are fully dependent on traditional methods. They first sort out the tiger prawn seeds (mainly the postlarval stage PL 20) accounting only 0.25–0.27% of the total catch and thereafter the major portion of the haul are thrown away on the beach flats or the tidal mudflats. This wasted by-catch contains the juveniles of economic and uneconomic varieties of finfish and shellfish along with a bulk of holoplankters and meroplankters (non-target species). This practice causes several ecological and occupational consequences, namely, (i) the huge destruction of the pelagic biota that can lead to severe stock depletion as well as hamper the energy transference through the marine ecosystem food webs; (ii) constant dragging of nets along the coast and tidal creeks paves the way for soil erosion, uprooting the mangrove seedlings and saltmarsh vegetation; (iii) the water quality is deteriorating in the catchment areas due to mud erosion and (iv) due to constant contact with the seawater, the collectors are affected with waterborne diseases, skin infections, reproductive tract disease in women and many other contagious diseases.This paper, in addition to identifying the challenge to environmental quality and resource abundance, emphasizes the need for grass-root public education so that local people come to understand, support and implement sustainable resource conservation and environmental protection activities now and in the future. As a follow-up course of action, the authors have initiated a general awareness program for developing consciousness among the coastal people regarding proper use of natural resources. Initiatives are taken for educating coastal people by holding workshops and seminars with the use of educational resource materials. Exclusive awareness camps and grass root level training for coastal people are also being proposed as a future course of action by means of exhibitions, audiovisuals etc. It is proposed that local government bodies come forward to mitigate this problem with scientific and rational approaches and to take proper actions towards conservation. [Copyright &y& Elsevier]

Investigates the decline of Penaeus monodon postlarvae (PL) in the Sundarbans mangrove ecosystem in Bangladesh. Impact of the horizontal expansion of shrimp farming on the decline of the wild resource; Correlation of water temperature and salinity with P. monodon PL abundance; Exploitation of inshore fishery of Hilsa ilisha.

The release of nutrients and anti-nutrients from mangrove leaf litter plays an important role in the biogeochemical cycling in aquatic environments and directly or indirectly affects water quality and food availability to shrimp. In this study, we assessed nutrient and anti-nutrient loss during decomposition of leaf litter at a concentration of 1 g/L for four mangrove species (Avicennia officinalis , Heritiera fomes , Sonneratia apetala , Sonneratia caseolaris) to monitor water quality and to estimate how leaf litter influences shrimp post larvae (PL) growth and survival. There were significant differences (P < 0.05) between the studied species in terms of mass loss of the leaf litter during the investigation period. There were also significant differences (P < 0.05) between the studied species in terms of loss of nutrients and anti-nutrients in the shrimp PL rearing tank during the four-week experimental period. Decomposing mangrove leaves stimulated availability of natural food for shrimp PLs. There was a strong positive correlation between mass loss and PL production. At the concentrations of leaf litter used, the anti-nutritional factors did not affect the PLs. PL survival with mangrove leaf litter was 75–82%, whereas all the PL died without any leaf litter. PL weight gain ranged from 0.83–3.33 mg/d where S. apetala leaf litter resulted in the highest PL growth rate, followed by A. officinalis, S. caseolaris and H. fomes, in that order (P < 0.05). Overall, mangrove leaf litter had a positive effect on shrimp performance in terms of growth and survival and this effect was highest for S. apetala leaf litter. • Nutrient and anti-nutrient content of mangrove leaf litter differs greatly between species. • The decomposition rate of mangrove leaf litter differs 2-fold between species. • Decomposing mangrove leaves stimulate availability of natural food for shrimp PLs. • Mass loss of mangrove leaf litter correlates with PL survival and production. [ABSTRACT FROM AUTHOR]

• Nine statistically significant risk factors of WSD were identified including DO. • Conventional PCR confirmed 46 WSSV positive shrimp farms whereas 47 by real-time PCR. • qPCR showed WSSV loads ranged from 5.62 × 109 to 2.01 × 1015 copies/g shrimp tissue. • VP28 gene sequence confirmed representative isolates as 100% identical with WSSV. • Highest WSSV prevalence (100%) was observed throughout the year in Khulna region. White spot disease has caused significant economic losses in the shrimp farming industry of Bangladesh over the last two decades. The responsible virus, WSSV, may show severe disease with significant mortality depending on farm management and environmental and seasonal changes. Data on farm management and environmental parameters were collected from the southwest region of Bangladesh in 2018, and WSSV infection was confirmed by the species-specific gene VP28 using conventional PCR, real-time PCR and sequencing. Through bivariate analysis, nine significant risk factors for WSD were identified, viz. farm age, presence of nursery pond, reservoir of PL, weed in farm area, control of weed, stocking density, stocking frequency, ammonia and oxygen concentration. This study detected 46 WSSV-infected shrimp farms by conventional PCR, whereas real-time PCR identified 47 WSSV-positive out of 49 farms. WSSV prevalence was highest in the Khulna region, with 100% positivity in all seasons. WSSV loads ranged from 5.62 × 109 to 2.01 × 1015 copies/g of shrimp tissue. The VP28 gene sequence confirmed that 15 representative samples were 100% identical to the 2018 WSSV strain of India. The relationships among risk factors, prevalence and severity of disease, and origin of WSSV strains could be impactful for WSD management. [ABSTRACT FROM AUTHOR]

Microplastic pollution has received increased attention recently due to potential threat to marine biota and human health. This study reports microplastic (MP) content in brown shrimp (Metapenaeus monocerous) and tiger shrimp (Penaeus monodon) inhabiting in the shallow and offshore waters of the Northern Bay of Bengal, Bangladesh. Gastrointestinal tract (GT) of shrimps (n = 150) were examined for MPs following alkali digestion, microscopic observation and chemical analysis by micro-Fourier Transformed Infrared Spectroscope (μFTIR). A total of 33 and 39 MP items were found in P. monodon and M. monocerous , averaging 3.40 ± 1.23 and 3.87 ± 1.05 items/g GT, respectively. Among various shapes, types and colours of MP, filament (57–58%), fiber (32–57%) and black (48–51%) were dominant amongst the various particles identified. Tiger shrimp had high numbers (23 items) of larger size fractions of MPs (1–5 mm) but brown shrimp had high numbers (15 items) of smaller MPs (250–500 μm), and μ-FTIR data confirmed 13 particles of polyamide-6 and 6 particles of rayon polymers. These results provide a baseline of MP contamination in seafood from Bangladesh that should be useful for future monitoring efforts. Image 1 • MP items in two shrimps were ranged 33–39 with a mean abundance 3.40–3.87 items/g GT. • MP particles were dominated by black fibers and filament. • MPs were composed of polyamide-6 and rayon polymers. • MPs may transfer to humans as shrimps are often eaten without removing the intestines. [ABSTRACT FROM AUTHOR]

Background: Due to its rapid lethal effect in the early development stage of shrimp, acute hepatopancreatic necrosis disease (AHPND) has been causing great economic losses, since its first outbreak in southeast China in 2009. Vibrio parahaemolyticus, carrying the pirA and pirB toxin genes is known to cause AHPND in shrimp. The overall objective of this study was to sequence the whole genome of AHPND positive V. parahaemolyticus strains isolated from shrimp (Peneaus monodon) of the south-west region of Bangladesh in 2016 and 2017 and characterize the genomic features and emergence pattern of this marine pathogen. Results: Two targeted AHPND positive V. parahaemolyticus strains were confirmed using PCR with 16S rRNA, ldh, AP3 and AP4 primers. The assembled genomes of strain MSR16 and MSR17 were comprised of a total of 5,393,740 bp and 5,241,592 bp, respectively. From annotation, several virulence genes involved in chemotaxis and motility, EPS type II secretion system, Type III secretion system-1 (T3SS-1) and its secreted effectors, thermolabile hemolysin were found in both strains. Importantly, the ~ 69 kb plasmid was identified in both MSR16 and MSR17 strains containing the two toxin genes pirA and pirB. Antibiotic resistance genes were predicted against β-lactam, fluoroquinolone, tetracycline and macrolide groups in both MSR16 and MSR17 strains. Conclusions: The findings of this research may facilitate the tracking of pathogenic and/or antibiotic-resistant V. parahaemolyticus isolates between production sites, and the identification of candidate strains for the production of vaccines as an aid to control of this devastating disease. Also, the emergence pattern of this pathogen can be highlighted to determine the characteristic differences of other strains found all over the world. [ABSTRACT FROM AUTHOR]