Extracting epidemiological knowledge of shrimp farmers applying participatory appraisal tools and mobile phone-assisted survey to identify and solve the problems of WSD

Participatory epidemiologists have emphasized that farmers have rich and detailed knowledge about the diseases of the animals they rear and the risk factors responsible for the diseases. Based on this conception a step-wise method where collegial participation of researchers and farmers was followed to gather qualitative and quantitative information to identify the possible risk factors of white spot disease (WSD) of shrimp. This proposed method consists of two phases: participatory phase that includes sampling of relevant farmers and identifying possible risk factors; and conducting survey and data analysis phase that includes mobile phone-assisted survey and statistical analysis. The advantages compared to traditional survey methods are that this method: i) brings researchers and shrimp farmers together in a participatory platform in identifying various risk factors associated with WSD, which is not possible by researcher-only surveys; ii) feeds the data of risk factors/variables to the mobile-phone assisted survey, in order to enhance the data quality through direct participation by the farmers and using mobile phones for data entry; and iii) supports multivariate statistical analysis, which is highly effective in identifying the relationships between potential risk factors and WSD in shrimp. Farm operator, the type of fertilizer used, water source (direct natural), presence or absence of a reservoir, and frequency of water exchange were the significant variables/risk factors found from the multivariate analysis most likely to be associated with WSD prevalence. Analysis of the collected data reveals that the major constraining variables identified by this participatory study were related to water management measures. Therefore, the WSD affected shrimp farmers do not need any expensive inputs from outside their communities but can solve the problem of WSD participatory manner with other stakeholders. A participatory model, as we proposed based on the results indicates that, DoF as the key stakeholder can play a leading role for organizing cluster of farmers and identify other stakeholders to solve the problems of WSD

Assessing the impacts of zeolite on water quality, growth performance, heavy metal content and health condition of farmed tilapia (Oreochromis niloticus)

The rapid expansion and intensification of tilapia (Oreochromis niloticus) aquaculture in Bangladesh results in an increasing tendency of administering more pharmaceuticals in fish health management. Hence, with the aim of investigating the effects of zeolite (a water and sediment treatment compound) on water quality, growth performance, hematology, gut microbial content, and heavy metal content of Oreochromis niloticus, an experiment was performed for 126 days in six experimental earthen ponds (each pond size is one decimal). The stocking density was 300 fry/decimal. Zeolite was applied directly into the water in treatment ponds at a rate of 200 g/decimal during pond preparation and 100 g/decimal/15 days intervals during the culture period as recommended by the manufacturing company. The results indicated that zeolite had a significant effect (p < 0.05) on all growth indices assessed in all three experimental stages (0–42 days, 43–84 days, 85–126 days) in treatment ponds compared to control ones, except condition factor (CF) at the first stage. Hematological results implied that the application of zeolite in treatment pond water had no significant effect on the red blood cell (RBC) and white blood cell (WBC) of experimental fish blood compared to the control. However, a significant effect on the blood glucose level and total viable count (TVC) of the experimental fish gut was observed due to the addition of zeolite in the treatment ponds. Zeolite supplementation in treatment pond water significantly reduced the concentrations of different heavy metals in pond sediment, water and fish flesh compared to the control. Therefore, zeolite could be recommended for administration in aquaculture. Further research is required to find out whether a higher or lower dose of zeolite improves the water quality, growth performance and health condition, and decreases the heavy metal content of fish or not

Performance evaluation of normal- and high-strength concrete column specimens reinforced longitudinally with different ratios of GFRP bars

Glass fibre-reinforced polymer (GFRP) bars, as reinforcement in concrete structures, have several desirable properties over conventional steel bars, such as high tensile strength, low density and resistance to corrosion. However, there are still some concerns about using GFRP bars as longitudinal reinforcement in concrete columns primarily due to their low compressive strength and low modulus of elasticity. It is evident that the compressive behaviour of GFRP bars as longitudinal reinforcement in normal strength concrete (NSC) and high strength concrete (HSC) columns has not been extensively investigated to formulate adequate design guidelines. In this study, 12 reinforced concrete column specimens were tested under concentric compression loading. All the tested column specimens were 600 mm in height and 154 mm in diameter. The column specimens were divided into two groups as per the compressive strength of the concrete used in casting the column specimens, which were 45 MPa and 90 MPa. Each group consisted of six column specimens, one plain concrete column specimen and five column specimens reinforced transversely with 6 mm steel helices spaced at 40 mm pitch (transverse reinforcement ratio ρt = 2.2 %). Out of those five column specimens, one had no longitudinal reinforcement (ρ = 0), one was reinforced longitudinally with steel bars (ρ = 2.4) and the rest were reinforced longitudinally with GFRP bars (ρ = 2.7, 3.2, and 4.3 %). From testing results, it was observed that steel and GFRP bar reinforced NSC column specimens exhibited two peak axial loads, with a higher second peak axial load than the first peak axial load, whereas steel and GFRP bar reinforced HSC column specimens exhibited one peak axial load only. It was also observed that the contribution of the longitudinal steel bars was about two times the contribution of GFRP bars in both NSC and HSC column specimens. Finally, the ductility of GFRP bar reinforced NSC column specimens was greater than the steel bar reinforced NSC counterpart, whereas this trend was the opposite in the column specimens cast with HSC

Can Bangladeshi pangasius farmers comply with the requirements of aquaculture certification?

Globally, Bangladesh is the fifth largest aquaculture producer, with pangasius (Pangasianodon hypopthalamus) contributing 18 % of the total aquaculture production. This production is characterized by unregulated farming practices, domestic trade without value addition, product development, or export. In this paper, the Sustainability Assessment of Food and Agriculture (SAFA) framework of the FAO was used to assess the competency of Bangladeshi pangasius farmers by comparing their practices with the indicators of farming practices prescribed by the Aquaculture Stewardship Council (ASC). A survey of 150 farmers was undertaken that investigated the SAFA dimensions of good governance, environmental integrity, production and economics, and social well-being. Of 57 indicators, only 35 % were met at the best/good level, most of which occurred in the production and economic (47 %) and environmental dimension (40 %) and the least in the social dimension (29 %). Therefore, improvement of farming practices in all of the SAFA dimensions is required, with social and environmental dimensions demanding the most attention. Aquaculture certification for Bangladeshi pangasius farmers also requires improvements in legal frameworks and the involvement of value chain actors. Under a research and development initiative, one method to improve compliance is to develop a best practices approach for cluster agribusiness cooperation in farmer groups that have to be contractually bound to processing plants. This can spread and make sale at the potential international whitefish market

Embryonic and Larval Development of Stinging Catfish, <i>Heteropneustes fossilis</i>, in Relation to Climatic and Water Quality Parameters

In terms of hatchery-based seed production, one of the most important aquaculture species in Bangladesh is the stinging catfish (Heteropneustes fossilis). Scientific and evidence-based embryonic and larval development research on this fish species in the context of climate change is limited. This experimental study was conducted via induced breeding of stinging catfish using a conventional hatchery system, rearing the larvae in hapas placed in ponds. A series of microscopic observations using a trinocular digital microscope and an analysis of the relationship between larval growth and climate-driven water quality parameters such as temperature, pH, dissolved oxygen, total dissolved solids, alkalinity, and ammonia were performed. During embryonic development, the first cleavage was observed between 30 and 35 min of post-fertilization. Embryonic development (ranging from the 2-cell to the pre-hatching stage) took 21:00 h. Hatching occurred at 22:30 to 23:00 h after fertilization, with an average larvae length of 2.78 ± 0.04 mm. In the post-hatching stage, four pairs of tiny barbels appeared at 36:00 h, and the larvae started feeding exogenously after 72:00 h. These larvae fully absorbed their yolk sacs on the 6th day and attained an average length of 6.44 ± 0.06 mm. Aerial respiration of the larvae was investigated through naked-eye observation on the 10th day of hatching. The average length of the larvae was 32.00 ± 2.0 mm at the end of the 30-day post-hatching observation period. Bivariate correlation analysis showed significant correlations between key climatic variables and water quality parameters under hapa-based larval-rearing conditions. According to canonical correlation analysis, the first canonical function revealed the highest significant correlation between the two sets of variables (r1 = 0.791). The response variable weight of larvae (6.607) was linked to two explanatory variables: pH (0.321) and dissolved oxygen (0.265). For the second canonical correlation function, a positive correlation (0.431) was observed between the two sets of variables. Larval weight (−18.304) was observed to be linked to climatic variables, including air temperature (−0.316) and surface pressure (0.338). Results of this study reveal the subtle correlation between larval growth and water quality driven by climatic variables

Perceptions of the Impact of Climate Change on Performance of Fish Hatcheries in Bangladesh: An Empirical Study

The impacts of climate change (CC) on all spheres of human life are evident worldwide. Fish is the premier protein source, and its production in Bangladesh is mainly dependent on hatchery-based seed production. However, hatchery productivity is disrupted every year due to CC. This study assesses the impacts of CC on fish seed production in hatcheries from the perspective of hatchery owners. A semi-structured questionnaire survey was conducted with 60 hatchery owners in five sub-districts (Trishal, Mymensingh Sadar, Gouripur, Fulbaria, and Muktagacha) of the Mymensingh district, the highest aquaculture-producing zone in Bangladesh. Characteristically, hatchery owners are middle-aged and highly educated, with over a decade of experience in fish hatchery management. Likert scale results showed that hatchery owners concur with the evidence of CC, as seen by changes in air and water temperatures, rainfall, and sunlight intensity, as well as frequent natural disasters. Regression analysis showed that erratic rainfall, high temperature, and high solar radiation significantly influenced the hatchery owners’ perceptions of CC. Principal component analysis (PCA) was used to divide the impact of CC into 12 components. Maximum variance (>70%) observed could be explained by problems related to embryonic and physiological development of fish fry, environmental changes, disease outbreaks, and poor growth of broodfish. The first PCA explained over 50% of the variances, with significantly higher factor loadings, comprising poor gonadal maturation, low hatching rate, poor egg and seed quality, low fecundity, and poor sperm quality of broodfish. The first PCA confirmed that the impacts of CC on fish hatchery operations were severe. Planting trees on the hatchery premises, aeration of brood ponds, increased water supply, and temperature control can be implemented to address the negative impacts on fish hatcheries. Further research in the laboratory and hatchery environments is needed

Economic Viability and Seasonal Impacts of Integrated Rice-Prawn-Vegetable Farming on Agricultural Households in Southwest Bangladesh

Integrated aquaculture is an efficient method to address food scarcity and land resources. This study analysed the impacts of integrated rice–prawn–vegetable farms (RPVF) compared with conventional rice farms (CRF) on farming households in southwest Bangladesh, in terms of cropping pattern, financial profitability and viability, and cash-flow. Data were collected through face-to-face recall interviews from farmers of CRF and RPVF. For RPVF, farmers cultivated diverse produce in the wet season, such as prawn/shrimp, carps in reservoirs and vegetables on dikes, and boro rice with vegetables in the dry season, whereas only rice was cultivated in both seasons for CRF. The annual hectare−1 net revenue from integrated RPVF was USD 2742.7, 3.6 times higher than for CRF (USD 756.6). RPVF had a higher undiscounted benefit–cost ratio (BCR) of 1.58 as compared with 1.34 for CRF. Net Present Value (NPV) and discounted BCR show that the integrated RPVF has higher potential and profitability than CRF. Year-round vegetable production and selling have resulted in a smooth cash-flow in integrated RPVF. Authorised extension agencies, such as the Department of Fisheries and Department of Agricultural Extension collaboratively can promote RPVF in other potential parts of Bangladesh, through which farmers can benefit year after year by investing farm income for the same farm and envisage food security

Economic Viability and Seasonal Impacts of Integrated Rice-Prawn-Vegetable Farming on Agricultural Households in Southwest Bangladesh

Integrated aquaculture is an efficient method to address food scarcity and land resources. This study analysed the impacts of integrated rice&ndash;prawn&ndash;vegetable farms (RPVF) compared with conventional rice farms (CRF) on farming households in southwest Bangladesh, in terms of cropping pattern, financial profitability and viability, and cash-flow. Data were collected through face-to-face recall interviews from farmers of CRF and RPVF. For RPVF, farmers cultivated diverse produce in the wet season, such as prawn/shrimp, carps in reservoirs and vegetables on dikes, and boro rice with vegetables in the dry season, whereas only rice was cultivated in both seasons for CRF. The annual hectare&minus;1 net revenue from integrated RPVF was USD 2742.7, 3.6 times higher than for CRF (USD 756.6). RPVF had a higher undiscounted benefit&ndash;cost ratio (BCR) of 1.58 as compared with 1.34 for CRF. Net Present Value (NPV) and discounted BCR show that the integrated RPVF has higher potential and profitability than CRF. Year-round vegetable production and selling have resulted in a smooth cash-flow in integrated RPVF. Authorised extension agencies, such as the Department of Fisheries and Department of Agricultural Extension collaboratively can promote RPVF in other potential parts of Bangladesh, through which farmers can benefit year after year by investing farm income for the same farm and envisage food security

Metagenomic assessment of the diversity and ubiquity of antimicrobial resistance genes in Bangladeshi aquaculture ponds

In Bangladesh, fish provide over 60% of animal-source food with 56.2% of this coming from aquaculture produced predominantly in rural freshwater ponds. Increasing demand for fish products is driving intensification and resulting in higher disease prevalence, posing a risk to food security. Biosecurity is often absent in rural aquaculture practices in Bangladesh and antibiotics are commonly used to treat and prevent disease outbreaks. Antibiotics are often administered incorrectly - a key factor associated with the development of antimicrobial resistance (AMR). AMR can be disseminated rapidly within microbial ecosystems via mobile genetic elements, posing a risk for humans and animals infected with AMR pathogens as treatments with antibiotics become ineffective. Early AMR detection and understanding of the spread of antimicrobial resistance genes (ARGs) in rural aquaculture practices is critical for both food security, human health protection and food safety. Here, we apply a metagenomic approach to assess the ARG composition in pond water from six finfish (tilapia and pangasius) farms in the Mymensingh division of North-central Bangladesh. We found microbial communities within the ponds had similar alpha and beta diversities, with multiple ARGs predicted to confer resistance to eighteen different classes of antimicrobials. The most common ARGs conferred resistance to aminoglycosides and sulphonamides and were present in taxa associated with both fish and human pathogens. This ARG diversity potentially confers resistance to a wide variety of antibiotic classes and questions the effectiveness of current and future treatment of diseases with antibiotics in earthen aquaculture ponds. The microbial and ARG compositions between fish ponds within each farm were similar, which may relate to parallels in farming practices creating similar microbial selection pressures and thus comparable microbial populations. Without a more controlled approach towards antibiotic usage, we will inevitably further exacerbate the challenges in treating and preventing disease outbreaks as aquaculture production intensifies in Bangladesh

Diallel Cross Application and Histomolecular Characterization: An Attempt to Develop Reference Stock of <i>Labeo ariza</i>

The objective of the present study was to evaluate the growth performance and genetic variation in diallel crosses of Ariza labeo (Labeo ariza) originating from three geographically separated rivers (Atrai, Jamuna and Kangsha) in Bangladesh. Intra (G1K♀K♂, G2J♀J♂, and G3A♀A♂) and inter (G4K♀A♂, G5K♀J♂, G6A♀K♂, G7A♀J♂, G8J♀K♂, and G9J♀A♂) stocks were produced following diallel cross (sex ratio—1:1 and n = 48; 16 from each river). Reproductive and growth performance, muscle cellularity and genetic variation following genotyping of eight microsatellite markers (Lr1, Lr2, Lr3, Lr22, Lr24, Lr27, Lr28 and Lr29) and analysis of all crossbreeds was performed. The fertilization (95% ± 2.11%), hatching (88% ± 1.03%), and survival rates (82% ± 1.88%) of G4K♀A♂ were higher compared to other groups. With respect to length and weight gains (2.67 ± 0.4 cm and 3.39 ± 0.2 g), SGR (3.23% ± 0.20%), and heterosis (8.87% and 24.74%) G4K♀A♂ was the superior group. A higher number of hyperplastic muscle fibers, mean number of alleles (2.75) and mean observed heterozygosity (0.417) from G4K♀A♂ could be interpreted to mean that G4K♀A♂ comprise better performance efficiency compared to others and are considered for continuing the L. ariza stock improvement program