Flood control,drainage and irrigation projects in Bangladesh and their impact on soils: an empirical study

The combination of a rising population and increased food demand has placed tremendous pressure on the land resources of Bangladesh. These pressures are exacerbated by the annual wet-season floods which frequently devastate much of the agricultural land. Successive governments have therefore sought international aid to assist in the development of flood control measures. Of particular importance are 14 major schemes which aim to provide protection from 20–25 year return floods by the construction of earth-embanked enclosures. There is no doubt that these schemes have been very successful in protecting valuable agricultural areas from floods and hence increasing agricultural production. There is, however, growing evidence from a range of sources for long-term deterioration in soil fertility within the project areas. The study reported here is the first to systematically examine the changes taking place in soil properties following the establishment of a flood control, drainage and irrigation project. Comparison of two soil series, sampled from within and without the project area, demonstrate that within six years of project establishment, significant adverse changes have occurred in several soil properties; these include increasing acidity and a decline in available nutrients. The changes are attributable to a combination of poor management strategies and the absence of the annual flood input of silt. As Bangladesh cannot afford any decline in agricultural output, it is vital to establish whether adverse changes recorded here are occurring in other projects. This can be achieved by the establishment of a nationwide programme of soil fertility monitoring. © 1998 John Wiley & Sons, Ltd.     

Efficiency of oxbow lake management systems in Bangladesh to introduce cage culture for resource-poor fisheries

A total of 5488 ha of oxbow lakes in Bangladesh has recently gained importance as a potential fishery resource. The growing need to utilize this resource to a fuller potential requires consideration of cage culture by resource-poor fishing communities as a compliment to existing stock enhancement programmes. In the present study, the existing management systems of eight lakes are reviewed. Water quality was analysed with reference to the largest lake, i.e. Lake Baluhar. During the present study, > 100 cm transparency indicated the suitability of a lake for cage culture. Other water quality parameters, especially dissolved oxygen, ammonia and nitrite concentrations, also indicated suitability for cage culture. Non-fisheries activities, such as the use of agricultural pesticides in the lake catchment and jute retting in its basin, were identified as the most harmful to fish by the majority of the fishermen. An integrated pest management programme using rice–fish based rearing systems in the lake catchment is recommended. It is further recommended that a unified management system should replace the existing dispersed systems under different management bodies.     

The use of allozymes at three life stages influences genetic variation analysis and clustering in Cicer arietinum germplasm collections

Levels of genetic variation using 6 enzyme systems for a total of 11 interpretable loci were examined in chickpea (Cicer arietinum) originating from 9locations in Bangladesh. The measurement of genetic variation at enzyme loci was carried out on the seed embryo, on the early leaves of seedlings and on the mature leaves at the vegetative stage. A total of 592individuals, including 240 seeds, 200 seedlings and152 mature leaves were investigated. Using electrophoretic data, chickpea was found to express higher percentages of polymorphic loci at the seed stage (36–64%) than at seedling (22–56%) or the vegetative stage (11–44%). The proportion of mean number of alleles and the average mean observed heterozygosity also were higher at the seed stage when compared to the seedling and vegetative stages. Unique alleles were absent, and only differences infrequencies could be noticed. Positive values of the fixation index were noted for pgm-1 and 6pg-1 for all stages and in both mnr loci for the seed embryo's. A trend towards lower genetic distances of all possible pairs of populations could be observed when comparing those of seed embryo's with seedlings or mature leaves. This trend was even more pronounced when pooling the data of 9 populations into their 3regions. Slight differences in genetic distances caused a separative clustering of population 3 at seed embryo, of population 2 at seedling and of population5 at vegetative stages. It is suggested that careful examination of enzyme polymorphisms at different developmental stages is a prerequisite before drawing conclusions on the genetic distance between germplasm collections from different origins since small differences in the data entry for clustering results in ties that may affect tree topologies. This revised version was published online in July 2006 with corrections to the Cover Date.     

Forest-based betel leaf and betel nut People in Bangladesh： approach Lawachara National Park （LNP） farming of the Khasia indigenous to biodiversity conservation in

An exploratory survey was conducted among the Khasia living in Lawachara National Parkt （LNP） to investigate their depend- ency on the protected area （PA） for livelihoods, betel leaf hill farming, traditional forest conservation and perceptions of the PA, Field data were collected by interviewing 48 household heads from two villages （punjis） located inside the LNP and visiting their farms.： The economy of the Khasia was forest-based. They were largely dependent on betel leaf hill farming in LNP and nearly 71% of their mean annual income was de- rived from this irrespective of farmer category. On average, about 14% of the incomes of the poorer farmers came from forest produce followed by 10% and 6% for medium and rich farmers respectively. Hills and forests were the foundations of their lives and livelihoods, and LNP was the life-blood of Khasia survival. As a sustainable production system, this farming practice plays a vital role in conserving biodiversity in LNP and might be replicated elsewhere.     

Qualitative risk assessment of transmission pathways of highly pathogenic avian influenza (HPAI) virus at live poultry markets in Dhaka city,Bangladesh

Analysis of environmental samples obtained from the Live Poultry Markets (LPMs) of Dhaka City, Bangladesh, has revealed that the highest degree of prevalence of highly pathogenic avian influenza A (HPAI, H5N1), besides other subtypes of the LPAI virus, poses the plausible risk of transmission of these viruses between human and poultry species. The present study was conducted using the OIE risk analysis framework to assess the risk level of each pathway successively. The estimated risk parameters were integrated towards to obtain the overall risk level for each specific HPAI transmission pathway using the matrix adapted by Cristobel Zepeda accompanying other expert consultations. The relevant data obtained from published and unpublished sources, together with survey data of field observations, were used to formulate and confirm the risk pathways and their associated risks. The results revealed that the risk of the release of the HPAI virus was medium when exposure was high. Additionally, the consequence would be considered very high with a medium degree of uncertainty for all parameters. Ultimately, the overall risk for transmission was estimated as medium with a medium degree of uncertainty. The findings of this study reveal that there is a significant threat that HPAI virus transmission could occur among poultry and humans and effectively sustain within the environment of the LPMs. Our findings are primarily focused on public health considerations, the hygienic slaughter of poultry and the relevant cleaning and sanitation practices conducted in the LPMs to support evidence‐based decision‐making processes. The findings of the study have the potential to be used to formulate effective risk reduction measures and can be further adapted in low‐resource settings without major infrastructural changes required of the LPMs. All of which would reduce the risk of HPAI virus release and further lessen the degree of exposure and transmission in established LPMs.     

Identification of male sterility maintainer lines for Ogura radish (Raphanus sativus L.)

‘Ogura radish’, a cytoplasmic genetic male sterile line, was crossed with four local and three Japanese cultivars to identify maintainer lines. Out of seven F₁ families, one cross involving a local cultivar, Aushi, produced 100% male sterile (MS) progeny. The crosses involving the other two local cultivars, Tangail Local and Kuni, produced about 90% MS progeny, indicating the presence of maintainer gene(s) for male sterility. The fourth local cultivar, Tasaki, produced 100% male fertile (MF) progeny. All three exotic cultivars appeared to possess the chromosomal gene(s) for controlling the male sterility. In BC₁, BC₂ and BC₃ generations, segregation of MS plants were more frequent when ‘Aushi’ was used as recurrent parent. The expression of male sterility was not affected by seasonal influences. Thus the local cultivar ‘Aushi’ may be used as maintainer line for ‘Ogura radish’. To produce hybrid seed, ‘Tasaki’ can be used as pollinator line as it exhibit high heterosis with ‘Aushi’. This revised version was published online in July 2006 with corrections to the Cover Date.     

Production and economic return of shrimp aquaculture in coastal ponds of different sizes and with different management regimes

Coastal shrimp (Penaeus monodon) aquaculture in Bangladesh is mostly practiced in a special type of field/pond situated by the side of a river -- called a Gher -- that is used to cultivate rice in winter and shrimp in summer. Ghers of different sizes are managed in different ways. In order to understand the effects of Gher size and their corresponding management practices on the production and economic returns of shrimp farming, we conducted an on-farm study in three small (1–5 ha), three medium (6–10 ha) and three large (>10 ha) Ghers located in the coastal Southwest region of Bangladesh. The mean harvest weight of shrimp was similar in all Ghers, but survival rates were higher in the small (50%) and medium (37%) ones than in the large (18%) ones. The high mortality in the large units led to a production that was lower than one-half of that in the small Ghers (about 80 and 200 kg/ha, respectively). The total variable costs per unit area were similar in all Ghers, but the importance of different items varied with Gher size. In the small Ghers, there are relatively high investments on inputs and labor. This expenditure results in lower shrimp mortality and higher production, which in turn results in gross returns that are larger than the total costs -- hence, a positive and high net return. In large Ghers, the fixed costs are larger than in the small ones simply because of the size of the pond. Variable costs include higher investments in post-larvae and labor than in small Ghers, and lower inputs applied only at pond preparation. This results in higher shrimp mortality and lower production, which in turn results in gross returns that are smaller than the total costs -- hence, a negative or low net return. These findings have positive implications for the future policy formulation of coastal shrimp aquaculture in Bangladesh.     

Nile tilapia (Oreochromis niloticus) seed production in irrigated rice-fields in Northwest Bangladesh—an approach appropriate for poorer farmers?

Participatory research was conducted with poorer farmers in two communities, Girai (G) and Bahagili (B) in NW Bangladesh to assess the production of Nile tilapia seed in irrigated spring rice-fields. All the selected households (G = 15; B = 4) had previous experience producing common carp (Cyprinus carpio) in the rice-fields allocated a separate plot in which a deeper area had been excavated for this trial. Mature GIFT strain Nile tilapia (12 female and 6 male; 121 ± 34 g and 158 ± 54 g size, respectively) were supplied to each household irrespective of the size of their trial plot (mean < 0.15 ha). The trial started in the spring rice season (boro) in February and ended at the end of main season (amon) in December 1999. Management practices, production and sales of fish were monitored weekly.The majority of farmers succeeded in producing fingerlings in their plots; 11% failed totally but around 70% produced more than 2000 fingerlings from a single plot. Production during boro and fallow period was much higher (> 90% total) than during the subsequent amon crop (< 10% total). Total production was highly variable among households but not different between the two study areas (G = 4092 ± 3277; B = 3730 ± 4232 fingerlings household^− 1). Daily production of fingerlings per unit area was relatively low (< 1 fish m^− 2 day^− 1) but efficiency of production was high, averaging 17.3 fingerlings. kg^− 1 female day^− 1. Mean individual harvest weight was 21 g.Most fingerlings were sold (43%) and/or stocked for further culture in their own grow-out system (39%), but some were used directly for household consumption (17%).     

Dynamics of floodplain fisheries in Bangladesh, results of 8 years fisheries monitoring in the Compartmentalization Pilot Project

Floodplain fisheries were monitored from 1992 until 2000 in the Compartmentalization Pilot Project in Tangail, Bangladesh. In permanent floodplains about 165 ± 28 kg ha^?1 of fish was caught annually. For seasonal floodplains, this figure was 83 ± 23 kg ha^?1 yr^?1. The fish catch exhibited a strong seasonal variation, with the highest catch in October, when the floodwater recedes towards the river, and the lowest catch during the dry season in April/May. The annual catch varied with the extent of flooding, with high catches in wet years and low catches in dry years. The extent of flooding was quantified through a Flood Index. Plotting the annual yields against this Flood Index provided a significant relation (P < 0.05), confirming the existence of a flood pulse. The fishing effort (f) and the catch‐per‐unit‐effort (CPUE) were significantly related (P < 0.05), whereby the fishing effort increased with increasing CPUE. The results are discussed within the frame of fisheries management in Bangladesh and highlight the need for long‐term data for proper evaluation of fisheries projects and the development of management schemes, and the difficulty of applying standard surplus production models in floodplain fisheries.