Southwest Coastal Region Of Bangladesh Research Articles

Impacts of climate change on shrimp farming in the South-West coastal region of Bangladesh

The inhabitants of south west region of Bangladesh are prone to floods, cyclones, salinity intrusion and droughts, and the incidence of these hazards is rising. Recently two cyclones (known as Aila and Sidr) hit the southwest region of Bangladesh. Considering the above in view, research had been conducted for understanding the impacts and adaptation measures through sustainable coastal resources management in the cyclone affected greater Khulna areas. The present study was carried out (from January to June, 2011) to understand impacts of climate change on the shrimp farming, hatchery and nursery operations in the selected upazilas (Paikgacha and Shyamnagar). The study was conducted both primary and secondary data sources. To collect primary data different methods had been adopted which were informal interview, a pre-formulated questionnaire survey and Focused Group Discussion (FGD). In the study areas, about 80-90% people are involved with shrimp farming with 10-15 years experience. About 60% shrimp farmers thought that the weather has changed abruptly within the last 5 years. The study showed that the first and foremost factor is high temperature (49.5%). Majority (43.21%) encountered that temperature hampered the farm operation while lower growth (54%), low production (19%), loss of crops (13%), less water (4%), mortality (4%), and diseases (4%) occurred due to less rainfall or no rain. From the study, farmers (80%) reported susceptibility of shrimp to diseases in body deformation, spots or lesions on skins while 13.33% mentioned fry susceptibility to diseases. Some time oriented and need based adaptations in shrimp farming are now most concern. Government and other stakeholders should come forward to execute research for adaptations.Res. Agric., Livest. Fish.3(1): 227-239, April 2016

Assessment of Salinity Hazard of Irrigation Water Quality in Monsoon Season of Batiaghata Upazila, Khulna District, Bangladesh and adaptation strategies

Batiaghata Upazila, Khulna District in south-west coastal region of Bangladesh is the mostly saline affected area, where agriculture activities are mainly dependent on rainfall. 23 water samples from surface water and shallow tube well (STW) were collected in the monsoon season and analyzed for physico-chemical properties to classify them according to salinity hazard. Electrical Conductivity (EC) of both surface and groundwater samples were slightly higher than that of acceptable limit ( Ca2+ > Mg2+ > K+ in both surface and groundwater while the anions trend in both surface and groundwater of the study area were Cl¯ > SO42¯ > PO43¯. EC and TDS showed high positive correlation with Na+, K+ and Ca2+ with Cl¯ as confirmed from Correlation Matrix and Principal Component Analysis (PCA). Most of the STW water samples compared to the surface water had higher Soluble Sodium Percentage (SSP) values while Sodium Adsorption Ratio (SAR) indicated the surface water and ground water with low sodium hazard. The Kelly’s ratio of STW water is more subjected to sodium hazard compared to surface water in the study area.

Migration Due to Climate Change from the South-West Coastal Region of Bangladesh: A Case Study on Shymnagor Upazilla, Satkhira District

Climate change has been presented as a likely trigger for migration of people, especially in Coastal areas in Bangladesh. This study investigates the climate-induced migration causes, migration pattern and destination of individual household in coastal Bangladesh. It also identifies which economic groups were migrated from this region. Data were collected through a stratified random sampling technique on 120 rural households through a defined questionnaire survey. Survey was carried out aftermath of AILA (25th May 2009), from three disasters prone unions in coastal Bangladesh. Findings showed that the main causes of migration were unemployment (65%), poverty and food insecurity (23%). The rate of temporary / seasonal migration (67%) was higher than permanent migration (20%) and most migrants choose city area (77%) as their migration place. Mainly lower economic groups (Extremely poor, poor and lower middle class) were migrated from this region for economic insufficiency. Creating job facilities and ensuring food security is the main solution for improving this problem.

Impact and Adaptation to Cyclone AILA: Focus on Water Supply, Sanitation and Health of Rural Coastal Community in the South West Coastal Region of Bangladesh

The objective of these study was to examine the impact of cyclone AILA on water supply, sanitation and health status in the southwest coastal region of Bangladesh and explore adaptation strategies. This study relied on field investigation where 120 respondents answers were collected randomly from three disasters prone unions in coastal Bangladesh through a defined questionnaire. Natural disaster was a common feature of the study area. The cyclone AILA hit the southwestern coastal region of the country in 25th May 2009.Water supply and sanitation condition became harshly disrupted during that time when it embraced various water borne diseases. Qualitative field data represented that about 67% people faced serious drinking water scarcity, especially during disasters and summer season due to the disruption of water supply facilities. In the study area, 97% households sanitation system were totally destroyed and 96% households could not use their sanitation facilities during disasters, unattainable sanitation technology was the main causes of these damage. Owing to poor water supply and sanitation facilities, people suffered from diarrhoea (32%) and dysentery (44%) diseases during the study conducted time. Tube-wells and latrines are build on an elevated base with improved floor and the excavation of ponds for salinity removal is the main adaptation approach for this area. Results drawn from this research and recommended adaptation strategies will be useful for local and national level planners, as well as international donors for preparing future disaster risk reduction plan.

Climate-induced human displacement: a case study of Cyclone Aila in the south-west coastal region of Bangladesh

The objective of this study was to explore the livelihood patterns and access to the local public services of the climate induced displaced people migrated by the Cyclone Aila in the south-west coastal region of Bangladesh. The study analysed a number of consequences, such as the causes of displacement, their demographic and socio-economic conditions, and their access to the local public services. Data were collected from four unions of three upazilas in the Khulna Division. The study employed a mixed method approach, where quantitative data were collected through a household survey, and qualitative data through focus group discussions, in-depth case studies, and participant observation. The results showed that the Aila affected displaced people were migrated to the nearby places due to their financial vulnerability, loss of physical resources, and insecurity, and they were suffering severely in terms of their unemployment, lack of housing, health problems, and their low access to the local public services. The findings would be important consideration for the disaster policy-makers, disaster mangers, and NGO workers.

Local perceptions of and adaptation to climate variability and change: the case of shrimp farming communities in the coastal region of Bangladesh

Shrimp aquaculture is the predominant farming practice in the southwest coastal region of Bangladesh and has been under increased pressure from environmental and climatic changes. To date, most of the studies examining farmer’s vulnerability and adaption to climate change have been agriculture-focused with little attention to the impacts on other livelihood systems. Based on a case study approach our study presents: i) how local people perceive climate change and whether it corresponds to meteorological records, ii) what climate change impacts people consider significant, and iii) what strategies the shrimp farmers employ to ameliorate perceived risks. This study was conducted using local climate data, focus groups and household survey in Mongla sub-district. This study shows that local people are aware of the changes in hydro-climatic parameters. Their accounts of climate change mostly diverge from the scientific evidence when long-term climate trends are considered, but on short-term variability, the correlation between scientific evidence and local perceptions is high. Repeated adverse impacts caused by climate stressors on livelihood activities shape people’s climate risk perceptions. In relation to perceived risks, farmers have made adjustments in their aquaculture practices. Yet, the level of responses clearly lags behind the extent to which concerns about climate disturbances are expressed. This is partly due to farmers’ efforts for managing transformation from agricultural livelihood system to aquaculture-based livelihood systems and partly associated with other social factors. This case study recommends governmental support for the shrimp aquaculture sector to facilitate the process of adaptation to changes in the hydro-climatic environment.

Cost-benefit analysis of shrimp cultivation in the south-west region of Bangladesh

This study conducted a cost-benefit analysis of shrimp farming in the south-west coastal region of Bangladesh. It finds a cost-benefit ratio of 0.77-0.88 for secondary dataset and 0.58-0.80 for primary dataset. The ratio increases for incorporating costs for household-level cooking-fuel, drinking water collection and such other indirect costs originated from shrimp farming intervention. In contrast, the ratio remains within 0.30-0.63 when only the direct cost and benefit components are considered and this is what the farmers usually observe and consider in farm-level decision-making. Therefore, farming decisions undermine invisible and unaccounted costs. The dilemma of higher visible economic return vs. invisible indirect costs of shrimp farming needs to be handled carefully through information dissemination among farmers regarding associated direct and indirect costs and benefits, establishing a clear set of rules, regulations and enabling policy and finally let the stakeholders to take final farming decisions which might facilitate sustainable practices for shrimp farming.

Effect of River Salinity on Crop Diversity: A Case Study of South West Coastal Region of Bangladesh

Saline water intrusion is a major problem and conflicting issue in south-west coastal region of Bangladesh. The increased salinity has negative impact on agricultural diversity in this region. The present study provides an assessment of perception of local farmers about changes of agricultural diversity mainly diversity of vegetable species (both summer and winter) and standing plants with the changes of salinity level in the nearby river. This study was carried out in January to August 2005 through semi-structured questionnaire in selected villages of different salinity prone areas such as high saline zone and moderate saline zone, namely Paikgacha and Rampal, respectively. The study has revealed that in Paikgacha, the salinity varies approximately within the range from 20,000 to 45,000 micro-mhos and in Rampal it is from 10,000 to 30,000 micro-mhos. Due to increased salinity, the summer vegetable species in Paikgacha and Rampal have been reduced from 16 to 2 and 15 to 9 respectively during the period 1975-2005. For winter vegetable species, this figure wasreduced from 13 to 9 in Paikgacha but in Rampal this number remained unchanged. Standing plant species in Paikgacha and Rampal have been reduced from 31 to 14 and 35 to21 respectively during that period. Agricultural diversity is reducing in substantial rate both spatially and temporally.Nepal Agric. Res. J. Vol. 8, 2007, pp. 29-37 DOI: http://dx.doi.org/10.3126/narj.v8i0.11576

Vulnerability of rural livelihoods to multiple stressors: A case study from the southwest coastal region of Bangladesh

The coastal area of Bangladesh has been a focus of climate change and hazard research due to its extreme vulnerability to tropical cyclones, often leading to disaster. While there have been recent studies on the nature of these disasters, people's vulnerability and responses, little is known about how other key stresses, interacting with these extreme weather events, impact natural resources and the flow of ecosystem services that sustain local livelihoods. In this paper, we explore the process by which major stresses and hazards shape the vulnerability of people's livelihoods in dynamic social-ecological environments in the southwest coastal region of Bangladesh. Drawing on qualitative and quantitative data from a case study, we identify the key drivers of change in social-ecological systems and evaluate whether these drivers have affected livelihood outcomes and various components of human wellbeing. This analysis suggests that increasing salinity intrusion, tropical cyclone and land-use change (directly and through changes in ecosystem services) affect the access to livelihood assets at household scale. This undermines social wellbeing by seriously impacting food and water security. Through identification of key stresses and their interactions, and the consequent impacts on ecosystems services and household capitals, the current study proposes a conceptual framework to understand the present day vulnerability to multiple stressors in the context of the coastal region of Bangladesh.

Impact of the Farakka Dam on Thresholds of the Hydrologic Flow Regime in the Lower Ganges River Basin (Bangladesh)

The variation of river flow within a natural range plays an important role in promoting the social-ecological sustainability of a river basin. In order to determine the extent of the natural range of variation, this study assesses hydrologic flow thresholds for the Lower Ganges River Basin. The flow threshold was calculated using twenty-two “Range of Variability (RVA)” parameters. The impact of Farakka Dam on the Lower Ganges River flow was calculated by comparing threshold parameters for the pre-Farakka period (from 1934 to 1974) and the post-Farakka period (1975–2005). The results demonstrate that due to water diversion by the Farakka Dam, various threshold parameters, including the monthly mean of the dry season (December–May) and yearly minimum flows, have been altered significantly. The ecological consequences of such hydrologic alterations include the destruction of the breeding and raising grounds for a number of Gangetic species, the increase of salinity in the southwest coastal region of Bangladesh and a reduction of fish and agricultural diversity. The major findings in this paper have a number of policy-level implications to aid water sharing mechanisms and agreements between the government of Bangladesh and India. The methodological approach presented in this study is applicable to other river basins.

Swimming alone? The role of social capital in enhancing local resilience to climate stress: a case study from Bangladesh

There has been increasing examination of resilience as a concept applicable to climate adaptation. In this paper, resilience is used to explore the layers of responses to past and present climate stress. It examines the factors and circumstances that may hinder or enhance resilience, providing insights into past and present adaptation processes that may be relevant for adaptation to future climate change. Specifically, this paper tests the value of social capital in influencing resilience to climate stress. While there are many examples where social capital influences resilience to climate stress, this paper aims to determine the relative importance of different types of social capital for enhancing resilience, by exploring how relationships of exchange and reciprocity influence responses to climate stress. This study involved case studies of specific communities in the southwest coastal region of Bangladesh. This case study highlights a complex rather than a uniformly positive relationship between social capital and enhancing resilience to climate stress. Specifically, it identifies four types of social capital-based support (with monetary support as a subset) and the interlinkages among the types (and processes) of social capital with diverse effects on resilience. It emphasizes the moral and ethical importance of reconceptualizing resilience with an emphasis on the most vulnerable, as resilience approaches that fail to recognize the differentiated nature of resilience, risk reinforcing vulnerability. Westernized concepts have important benefits, but crucial limitations when applied to the particular conditions, value sets and modes of community working in the south. The uncritical importation of social capital needs to be treated with caution, especially in the context of climate adaptation.

Impacts of Different Agro-Ecological and Management Practices on the Shrimp Productivity of <i>Ghers</i> in the Southwest Coastal Region of Bangladesh

The study was undertaken to investigate the impacts of water and soil quality parameters, and management practices on shrimp productivity of ghers in three agro-ecological areas of Paikgacha, Shyamnagar and Rampal in the greater Khulna district of Bangladesh. Five ghers of existing culture systems from each of three locations were selected for this study. Findings revealed that water quality parameters including salinity, alkalinity and dissolved oxygen contributed significantly (p<0.05) and positively to shrimp productivity. Phytoplankton production also showed a positive correlation with shrimp productivity. Soil quality parameters including salinity, potassium and calcium content showed positive correlations with shrimp yield. In relation to management practices, stocking density, sources of PL form natural sources and supplementary feeding showed significant (p<0.05) and positive correlations with shrimp productivity. Water exchange also showed a positive correlation with shrimp yield.DOI: http://dx.doi.org/10.3329/pa.v18i2.18170 Progress. Agric. 18(2): 149 - 155, 2007

Impact of Climate Change on Food Security in South-West Coastal Region of Bangladesh

The study was carried out during March to April 2010 to identify the impacts of climate change on food security in context of southwest coastal region of Bangladesh and to Original Research Article American Journal of Experimental Agriculture, 4(12): 1916-1934, 2014 1917 address appropriate strategies to overcome it. Multistage sampling technique was adopted to select the households. Four villages of 3 unions of Dacope upazila were selected purposively from 9 upazilas of Khulna district. Twenty households were taken from each selected village. The heads of households were taken as the respondents to carry out the survey. Collected data were analyzed to identify percentage, mean, standard deviation, standard error of mean using statistical software SPSS 16. The study demonstrated the sources of income in two time periods: 2010 and 2003. In 2003, 62.5% of the respondents were engaged in agriculture, followed by 22.5% in fisheries, and 5% in small business. There happened a drastic change in income sources due to compulsion by climate change. In 2010, share of agriculture was drastically declined to 47%, whereas, fisheries increased to 27% and similarly, share of small business and day laborer increased to 7% and 5% respectively. Study revealed that cyclone resulting 89% respondents to shortage of drinking water, followed by 75%, 65%, 50%, and 42% to food shortage, property loss, homeless, and decreased production respectively. Most of the respondents were unable to fulfill their daily needs as there was a gulf of differences between the income and expenditure of the people of the study area reflecting the extent of misery of coastal lives. Alternative livelihood adaptation practices such as cultivation of vegetables on floating bed, multi cropping, salt tolerant crop or cultivation of beans, gourds and other vegetables on embankment’s surrounding should be adapted.

Fish-Paddy Crop Rotation Practice In South- West Coastal Region Of Bangladesh: A Profitable Technology For The Poor Farmers

The study was conducted at the farmer’s pond at Sadar Upazilla of Bagerhat District, South-west coastal region of Bangladesh during the period from May 2006 to April 2007 to understand the present status of crop rotation practice and assess the production and cost benefit ratio of the existing culture practices. Two treatments viz., the crop rotation with paddy (T1) and the shrimp-prawn-fish culture (T2) were used in the studies. Shrimp (Penaeus monodon), prawn (Macrobrachium rosenbergii), and catla (Catla catla) were stocked at 20000, 10000, and 250 individuals/ha, respectively, in both treatments. In T1, aquaculture phase was from May to December 2006, and the episode of paddy (BRRI dhan 28) cultivation was initiated after full harvest of aqua products and continued till April. Similar farm inputs were given for the common components in both the treatments. Shrimps were harvested four months following stocking in both T1 and T2 treatments.. In T1, production of shrimp, prawn, and catla were 347.20, 355.35, and 140.4 kg/ha, respectively and in T2, productions were 354.38, 432.37, and 204.7 kg/ha, respectively. In T1, total paddy production was 6200 kg/ha. Net benefit in T1 and T2 was Tk. 300,477 and Tk. 262,561/ha, respectively. DOI: http://dx.doi.org/10.3329/bjar.v38i3.16924 Bangladesh J. Agril. Res. 38(3): 389-399, September 2013

A molecular insight of some probiotic bacteria to address their antagonistic activity against pathogenic vibrios causing shrimp mortality

The molecular basis of antagonistic activity of a number of probiotic bacteria was analyzed using plasmid curing method. Earlier, six bacteria having potential probiotic activity under laboratory conditions were screened from 96 isolates which were obtained from shrimp rearing environment from south-west coastal region of Bangladesh. Among the isolated probionts, five were subjected to plasmid curing method and three were found to harbor plasmids, as was revealed in an agarose gel electrophoresis. Curing of these plasmids demonstrated that the bacteria lost its antagonistic activity, indicating the activity could be plasmid-borne. The antagonistic activities of the rest two isolates however, were not plasmid-oriented as no plasmid was recovered from them. DOI: http://dx.doi.org/10.3329/jbas.v37i1.15688 Journal of Bangladesh Academy of Sciences, Vol. 37, No. 1, 115-120, 2013

Monitoring the presence of chloramphenicol and nitrofuran metabolites in cultured prawn, shrimp and feed in the Southwest coastal region of Bangladesh

Presence of nitrofuran and chloramphenicol in farmed prawn and shrimp is a major concern in the export sector of Bangladesh. Rejections of consignments by the foreign buyers have been recurrent for the last couple of years due to detection of these banned antibiotics. The increasingly complex requirements for food safety assurance and traceability set by major export markets represent a threat to the trade of this significant sector. In this study, the status and trends of the presence of nitrofuran and chloramphenicol in freshwater prawn Macrobrachium rosenbergii (De Man) and marine shrimp Penaeus monodon (Fabricius) and in their feeds in the Southwest coastal region of Bangladesh were investigated. The prawn/shrimp farmers, feed manufacturers and feed sellers were interviewed with well structured pre-tested Questionnaires. Antibiotic residues present in the animal muscles, feeds and feed ingredients were detected using LC–MS–MS by the Fish Inspection and Quality Control Wing of the Department of Fisheries. The study reveals that farmers did not deliberately use those banned antibiotics, but these chemicals were detected in many M. rosenbergii and P. monodon samples in 2008, 2009 and 2010, in both fresh muscles, pre-export and post-export consignments. The percentage of contamination with this banned antibiotics in M. rosenbergii samples were 17.74%, 22.89%, 13.60% and in P. monodon samples were 12.65%, 15.79%, 11.85% in 2008, 2009 and 2010 respectively. Antibiotic residue data of 2008, 2009 and 2010 showed: (i) contamination of nitrofuran and chloramphenicol was more in M. rosenbergii than P. monodon; (ii) among four nitrofuran metabolites, nitrofurazone was found more frequently but in smaller quantities in 2009 and 2010; (iii) contamination of nitrofuran metabolites was more in prawns fed with commercial feed than those with home-made feed; and (iv) there has been a decreasing trend of the presence of nitrofuran and chloramphenicol in prawn and shrimp of Bangladesh.

Hydro-Meteorological Trends in Southwest Coastal Bangladesh: Perspectives of Climate Change and Human Interventions

The southwest coastal region of Bangladesh, being under tidal influence and dependent on sweet water supplies from upstream, has a unique brackish water ecosystem. The region, having vast low-lying areas enclosed by man-made polders, is considered to be highly vulnerable to climate change induced hazards. In this study, linear trends in hydro-climatic variables, such as temperature, rainfall, sunshine, humidity, sweet water inflow and tidal water level in the region are assessed using secondary data and following both parametric and nonparametric statistical techniques. Correlation between the sweet water flow from the Gorai River, a major distributary of the Ganges River, and the salinity level in the Rupsa-Pasur River near Khulna, a southern metropolis, is also investigated. The results reveal that the temperature in the Khulna region is increasing at a significant rate, particularly in recent years. The number of extremely cold nights is decreasing and the heat index is increasing. The sunshine duration has a decreasing trend and the humidity has an increasing trend. Rainfall is increasing in terms of both magnitude and number of rainy days. However, the annual maximum rainfall and the number of days with high intensity rainfall have remained almost static. The annual maximum tidal high water level is increasing and the annual minimum low water level is decreasing at a rate of 7 - 18 mm and 4 - 8 mm per year, respectively. There is a negative correlation between the Gorai flow and the river water salinity around Khulna. Dredging of the Gorai during 1998-2001 resulted in an improvement of the salinity situation in the Khulna region. The variation in water salinity, tidal water level and sweet water flows in different time periods indicates that the human interventions through upstream diversion and coastal polders have contributed more in hydro-morphological changes in the southwest than the climate change. However, there are some evidences of climate change in the meteorological variables at Khulna.

Evaluating pond sand filter as sustainable drinking water supplier in the Southwest coastal region of Bangladesh

This study investigates existing water supply scenario, and evaluates the performance of pond sand filter (PSF) in meeting drinking water demand of Dacope Upazila in southwest coastal Bangladesh. Questionnaire survey to the villagers reveals that PSF is the major drinking water sources (38 %) of the study area followed by tubewells (30.4 %), rainwater harvesting (RWH) systems (12.6 %), ponds (10.3 %) and others (8.7 %). The spot test and laboratory analysis show that odour, colour, pH, dissolved oxygen, hardness, calcium, magnesium, nitrate, sulphate and phosphate of the PSFs water meet Bangladesh standard. The efficiency of PSF in reducing total dissolved solids (TDS) (15 %) and potassium (8.2 %) is not enough to meet the standard of 20 % PSFs for TDS and one-third PSFs for potassium. The study proves that PSF is unable to remove coliform bacteria by 100 % from highly contaminated water. Hence, disinfection should be adopted before distribution to ensure safe drinking water. Majority of the PSF’s users (80 %) are either partially satisfied or dissatisfied with the existing system. The beneficiary’s willingness to pay for drinking water technologies seems that the combination of PSF and RWH could ensure sustainable drinking water in coastal region of Bangladesh.

Social supremacy and its role in local level disaster mitigation planning in Bangladesh

PurposeThis paper aims to discuss issues related to disaster mitigation planning provisions in Bangladesh, one of the most disaster‐prone countries in Asia. It seeks to concentrate on the issues related to the role of local groups in establishing cyclone shelters.Design/methodology/approachIn February 2008, a field study was conducted in the Southwest coastal region of Bangladesh. Combining the most recent empirical data, the location of cyclone shelters and the social supremacy structure are explored in this paper. Vulnerability due to infrastructure is defined here on the basis of available infrastructural facilities i.e. cyclone shelters, by using catchment area analysis in the geographical information system (GIS) software ArcGIS. The paper bases its argument on the assumption that the location of an infrastructure item like a cyclone shelter is dependent on the influential and motivational power of local elites and not on the necessity of the deprived people. Vulnerability, from this perspective, is interpreted in this study as a result of socio‐political supremacy in establishing cyclone shelters in coastal regions of Bangladesh.FindingsThe results indicate that locally supreme groups are located the closest to the cyclone shelter and may control local‐level disaster mitigation planning.Research limitations/implicationsThe paper outlines the “social supremacy” concept based on one rural union and the communication rationalities of the general people. Both describe the ways of identification, the social spectrum of public interests as well as the decision‐making process in rural Bangladesh.Originality/valueThe paper contains valuable information regarding rural society and its socio‐political structure as well as planning problems in coastal Bangladesh.

Characterization of water quality in shrimp ponds of different sizes and with different management regimes using multivariate statistical analysis

Coastal shrimp aquaculture in Bangladesh is mostly practiced in an agricultural unit called a Gher, which is a special type of agricultural field with elevated surrounding embankments/borders situated by the side of a river that is used to grow rice in winter and shrimp in summer. Ghers of different sizes are managed in different ways. An on-farm project was carried out to study the effects of Gher size and their related management practices on water quality, shrimp production and the economic returns of shrimp farming in the Southwest coastal region of Bangladesh. We present here the results of this project with respect to water quality as explored through factor analysis, which was applied as a way to understand the nature and extent of the effects of different variables. For the majority of the variables and factors, one-half to two-thirds of their variability was explained by changes over time (months), and a further one-quarter to one-third was explained by Gher size and associated management practices. The alternating dry/monsoon season and water management practices determined long-term and large-scale (annual) water exchange in the Ghers that mainly affected processes related to live and dead particles suspended in the water column. Processes related to decomposition and nitrification were more dependent on short-term (days) water circulation in the Ghers, which is turn was reliant on the time span between the exchanges of water in the Ghers and river. Our results show that improved management leads to higher natural and shrimp productivity in the smaller Ghers and strongly support the argument put forward by the policy makers and scientific community in Bangladesh that the smaller the Gher, the better they can be managed and the better the possibility of increased shrimp survival and production.