GENERAL
A vast tract of low lying tidal flood plain in the coastal area of Bangladesh is flooded twice in a day. For many years, these lands used to be protected by dwarf embankment under the initiative of local Zamindars. Paddy cultivation in rotation with fish production were the main activities of the people of the area.
Dykes constructed by the Zamindars were of inadequate section, low quality and required continuous maintenance. Dykes often collapsed due to hydrostatic pressure and errossive action of wind and current. Drainage facilities provided were also inadequate.
After abolition of Zamindari system in Bangladesh, the Government started construction of Coastal Embankment Project in 1961 under USAID assistance. An area of about 5000 sq. miles were given protection in the districts of Khulna, Barisal, Noakhali and Chittagong.
The Coastal Embankment Project was intended to increase agricultural production by preventing saline water inundation, reducing the flood hazards and preserving sweet water in the internal channel system. Effect of river confinement and future land use pattern were not taken into consideration and century long practice of paddy-cum-fish culture were stopped. An important consequence of the river confine ment was the rapid river siltation. This problem was very much pronounced in the western zone of the delta and many of the drainage sluices could not effectively function during the monsoon result inundation within the polders.
Coastal Embankment Project, however, has provided a favourable infrastructure for the spread of brakish water aquaculture and with the increase of shrimp price in the world market, many entrepreneurs started shrimp culture in many scattered locations in poldered areas disregarding the ban on entry of saline water within BWDB Poldered areas.
Incentive gained by shrimp culturists is quickly responding by gradual encroachment into paddy area. The present day culture is different from the paddy-cum-fish culture of the pre CEP times. Particularly in Satkhira area. Expansion of shrimp farms are affecting paddy production, livestock and domestic forestry. Since shrimp culture is less labour intensive, the question of labour employment may be a buring problems if shrimp farming expands in leaps and bounds. Future planning should, therefore, strike a balance between all these constraints and a fair income distribution.
HYDROLOGY
Hydrology of the coastal plaints of Bangladesh presents a complicated interaction of fresh water flow from the upstream, the tides and tidal flows from the Bay of Bengal Tropical Cyclones, storm surge and other meteorological effect from the sea and the physiography of the coastal plaints.
Projects concerned for these areas has to be planned and designed to utilize the available resources and to stand against constraints. In a complicated area like this there can be large number of alternatives for development whereas some of hydrologic elements may be constraints to some projects the others may be advantageous. As an example, salinity is a constraint for rice farming whereas it is a resources for shrimp culture.
Hydrology chapter is, therefore, intended to provide a general picture of the Hydrologic elements in the area - data from which may be used for general planning and selection of alternatives for further intensive study at which stage further data collection may be necessary for design of the project selected for implementation.
Hydrological Setting, Topography and Geology presents a general hydrologic environment of the area. Rainfall, tidal levels and flows and salinity distribution are major hydrologic elements that will affect planning of any schemes for the area. Rainfall is a resource for agricultural activity but along with dominant tide levels may create serious drainage problems. As such, frequencies of both these elements have been provided.
Salinity has its variation round the season. With the on-set of monsoon the salinity profile recedes and with the withdrawal of monsoon the salinity profile invades island.
Salinity intrusion at any point depend upon salinitant sea face, rate of diffusion of the intruded salinity and the fresh water flow from upstream. In localised basin areas, rate of exchange of basin water with the river flow any create difference in salinity. In order to high light this situation experimental results for two selected basins have also been included.
The climate and rainfall distribution of the area is of tropical nature dominated by south-west monsoon of the Indian Ocean. There are three distinct season. The warm season lasts from March to May. The highest temperatures of the year occur during this period. About 15% of the annual rainfall occur during this period mainly as thunder storm.
The monsoon season normally begins in June and continues through October. Minimum temperature may 90°F, humidity approach the saturation point, skies are overcast and 75% to 80% of annual rainfall occur during this period. Most of the destructive cyclone storms occur during pre-monsoon and post monsoon period, i.e., April-May and Oct.-Nov.
The cool season extends from November through February and is generally pleasant and confortable. Rainfall is infrequent, the minimum temperature vary from 45°F & 50°F and skies are generally cloudless.
Annual rainfall in the coastal area varies from 1200 mm to 4400 mm and rainfall increases towards sea as will be evident from annual fainfall isohytes.
The tide in the Bangladesh coast is semidiurnal with significant diurnal inequality. This diurnal inequality in successive high tide may range up to 1.5 to 2.0 ft. which is likely to have significant influence on the planning of tidal inundation or drainage project. Apart from fortnightly tide, the high tide starts increasing from January and attains highest value in July-Sept.
With the increase of high tide, the salinity also increases, attains highest value during April/May and starts rapid falling after June.
Records of salinity at Khulna shows that salinity may rise from a few hundred micro mhos/cm in January/February to about 10,000/13,000 micro mhos/cm in April/May.
In Satkhira area, where salinity is normally high, the variation is, however, lower. For example, in January/February, the salinity is 5,000 to 7,000 micro mhos/cm and this may to upto 30,000 micro mhos/cm in April and May.
It may, however, be noted that Khulna area receives monsoon flow from the Ganges through Gorai. As such, recession of salinity in Khulna area depends upton arrival of monsoon flow from the Ganges. In the western part, i.e., Satkhira area the recession of salinity depends mainly on the premonsoon and monsoon rainfall.
In Cox's Bazar area, the estuaries under the dominance of Matamuhuri river salinity responds quickly with the rise and recession of the flow of the river. A strong inverse co-relation has been formed between salinity of sample stations, with the Matamuhuri flow. The rapid recession of salinity depends upon the rainfall over Matamuhuri catchment.
SOIL AND LAND POTENTIALITIES
The soils of the tidal area have been broadly classified depending on parent materials, topographic situation etc. into three catagories:
Grey floodplain soils,
Acid sulphate soils, and
Calcareous alluvium.
Grey floodplain soils both include saline and non-saline soils and are developed in non-calcareous alluvium. They occupy middle Meghna and Ganges tidal floodplains as well as areas in the old Meghna estuarine floodplains, and in the Chittagong coastal plain. These soils are shallowly to deeply flooded in the monsoon season, but mainly dry in the dry season, except in some basin centre.
Acid sulphate soils occupy the Khulna and Chakaria Sundarbans, and small areas adjoining them. These soils resemble grey floodplain soils in the wet state, but they become toxically acid if allowed to dry out. This soils mainly occur under mangrove forest and are tidally flooded with salt water for most or all of the year.
Calcareous alluvium includes the soils of the Ganges floodplain and the young Meghna estuarine floodplain. Flooding is mainly deep in the Ganges floodplain while in the young Meghna estuarine floodplain it is shallower and tidally controlled.
The soils of the sample areas (Satkhira and Chakaria Sundarbans) belong to the Ganges floodplain and acid sulphate soils respectively.
Field Investigations
Field investigations were carried out in the sample areas to assess the impact of shrimp culture in relation to rice cultivation. Two sets of tests were carried out. Firstly, a complete profile of the soils were analysed so is to correlate the soils of the observation points with the soil series identified by the Soil Resources Development Institute; secondly, samples were collected mainly for a period of 8 months, starting from October 1982 to May 1983 for determination of soil-water chlorinity.
Physical Properties
The soils of the Satkhira areas do not pose any problem for agricultural production (mainly transplanted Aman) but soils of Chakaria Sundarbans are toxic and unsuitable for agricultural production.
Concluding Observations
Under average rainfall conditions shrimp culture does not seem to have any damaging effect on rice cultivation since rain and fresh river water inundation prevent accumulation of salt. But with less than normal rainfall and specially when the soil surface is exposed to accumulation of salt by copillary rise in the top layer if is generally observed to result in reduced crop yields.
BIOLOGY
The present investigation was carried out in three areas: (i) Chakaria, (ii) Khepupara, and (iii) Satkhira areas, which come under the tidal areas of Bangladesh and form the major nursery ground of shrimp, fin fishes and other organism's. The aim of the study is to gather some knowledge on ecology, community structure of plankton with special reference to shrimp post larvae and benthos of the areas. This report includes informations on:
Physico-chemical parameters of waters of the areas.
Population composition and seasonal abundance of zooplankton of the area with special reference to commercially important shrimp post larvae.
Population composition and abundance of organism's of beam net catch with special reference to settlement of juvenile shrimps at Chakaria and Satkhira area.
Abundance and seasonal distribution of macrobenthos in fish ponds of the three areas.
Analyses of fish fauna of the Behundi net catches in the three areas.
Analyses of harvests from the fish ponds in Chakaria and Satkhira area.
The average water temperature of the three areas was more or less similar and the water temperature was always found to be influenced with distemperature.
The average secchidics depth was remarkable high at Chakaria and the highest was noted in the winter (97.5 cm) and the secchidisc depth dropped suddenly (22.7 cm) as the monsoon approached. A similar treand in fluctuation of secchidisc vigibility was noted in Khepupara (31 cm - 9 cm). On the contrary the fluctuation in secchidisc vigibility was the minimum in Satkhira (14.25 cm - 7.42 cm) and the vigibility was high in monsoon and low in autum and winter.
The average pH of water at Chakaria and Satkhira was 7.4 and 7.3 respectively whereas that of Khepupara was 6.8.
When the yearly average content of dissolved oxygen is considered the highest was recorded in Khepupara (5.9 ml/l) and the lowest was noted from Satkhira (4.39 ml/l) whereas the Chakaria area stood in between the two areas (5.4 ml/l).
The highest amount of monthly mean salinity was recorded in the waters of Chakaria (16.2% O) and the lowest in Khepupara (6.9% O), whereas at Satkhira it was 13.7% O. A drastic decline in saline content was found during monsoon at Chakaria (9.9% O to 1.9% O, 11.7% O to 2.8% O) and at khepupara (11.8% O to 3.19% O). On the other hand more or less a gradual drop in saline content was found in waters of Satkhira.
The highest orrurrence of zooplankton was noted at Chakaria area (Monthly average 418.248/m3) and the lowest at Khepupara (125.760/m3). The Satkhira area also supported a reasonably high concentration of zooplankton (monthly average of 309.841/m3).
The concentration of total organism was recorded to be high during night at surface in all the three areas of observation.
The density of shrimp larvae was more or less similar at Chakaria (monthly average abundance of 4.328/m3) and at Satkhira (monthly average of 4.22/m3). The lowest density of shrimp larvae was recorded at Khepupara (monthly average abundance of 1.085/m3).
The maximum number of shrimp larvae was recorded from June to August at Chakaria and Satkhira area whereas the density was high from November to January at Khepupara. The peak occurrence was noted in June (16.73/m3) at Satkhira and in July (22.272/m3) at Chakaria. The highest density was found in November (3.316/m3) at Khepupara.
At Satkhira area 1.36% of total organism's were shrimp larvae whereas at Chakaria 1.035% of total organism were shrimp larvae. At Khepupara only 0.862% of total organism were shrimp larvae.
The penacid shrimp occupied 0.919% of total founa with the maximum density of 26.807/m3 in July at Chakaria area. The Satkhira area was found to hold more or less simillar concentration (0.92% of total founa) of penacid shrimp with the peak (11.37/m3) in June. At Khepupara the penacid shrimp was recorded to constitute only 0.29% of the total organisms.
Of the penacid shrimps four species viz. Penacus monodon, P. indicus, Metapenaeus monoceros and M. brevicornis were noted to be the major founa at Chakaria and Satkhira area. Among these organisms Penaeus monodon was found to be the dominant founa at Chakaria area with the monthly occurrence of 1.707 indv./m3). At Satkhira area Metapenaeus monoceros was the dominant species among the penacid shrimp (monthly average occurrance of 1.142 organism/m3). Among the penacid shrimp, Penaeus monodon P. indicus, Metapenaeus monoceros were recorded from Khepupara and P. monodon was the dominant species among the penacid shrimp.
In the present observation the highest density of organisms in beam net catch was recorded at Chakaria area, the frequency of the occurrance was lesser in Satkhira. Of the penacid shrimp, Penaeus indicus was the dominant species at Chakaria whereas Metapenaeus monoceros occupied the highest position at Satkhira in beam net catch.
A remarkable difference in the seasonal abundance of macro-invertebrates was noted between ponds of two areas. The Chakaria area showed rich population during winter whereas Satkhira area during rainy season.
The highest density of shrimps at Behundi catch was recorded at Satkhira (505.6 indv/Kg.) and the lowest at Chakaria (172.5 indv./Kg.). The Khepupara area occupied the second position (492.9 indv./Kg.). Metapenaeus monoceros and M. brevicornis were the dominant species in all the three areas. Penaeus monodon and P. indicus were found to be common in all the three areas.
The fishes in ‘Behundi catch’ were noted to be dominant at Khepupara (monthly average of 279.08 indv./Kg.). The Chakaria area ranked second position (monthly average of 249.30 indv./ Kg.) and the Satkhira came third (monthly average of 244.5 indv./Kg.). Hilsa ilisha was found abundantly at Khepupara whereas Harpodon nehereus and Mystus qulio were dominant species in Satkhira. Mugil tade showed the highest occurrance in Chakaria area.
AGRO-AQUACULTURAL ECONOMIC STUDY
The areas surveyed for the agro-economic study include Satkhira, Ashasuni, Debhata and Kaliganj upazilas in the Satkhira district and Chakaria Sundarban upazila in the Cox's Bazar district. The presently utilized as well as prospective areas for brackish water fish culture, in the selected poldered area, (where Hydro-Biologic Survey was considered) were treated as sampling universe. The two-stage stratified random sampling technique was used as sampling design for the survey. In Satkhira area a random selection of 10 percent of villages was made to constitute the first stage sample, from which 10 percent households from each selected village formed the second stage sample representing one (1) percent of total house holds of the sampling universe. In case of Chakaria area, 50 percent of the villages was taken as the primary sampling unit and 10 percent of households of each selected village constituted the secondary sampling unit. The parameters considered pertinent to the agro-economic profile of the study area population are narrated in the sections following.
Population
The age structure in Satkhira area shows a clear preponderance of relatively younger population. The population not exceeding nine years of age constitutes 35%, whereas this group accounts for 29% in the total population of the country. The age group below 15 years is formed by 46%, which is 5% above the national figure. The proportion of the labour force group (15–59 years) accounts for 50% compared with 54% in the population of the country. The age group of 60 years and above is formed by 3.2% of the study area population and 4.5% of the country's.
Chakaria area is also characterized by predominance of younger population. In fact its predominance here is more manifest than in Satkhira. The age group of 0–9 years constitutes 39%, which is to a little higher than that of Satkhira. The below 15 years segment accounts for 48.5%, which is 2.5% higher than that of Satkhira. The working age cohort is much smaller here accounting for only 37.6 percent; this group in Bangladesh and in Satkhira is represented by 54% and 50% respectively. The age group of 60 years and above is also of a much smaller size.
Land Ownership and Tenurial Structure
In the Satkhira survey area, the proportion of owner having not more than one acre of land is found fairly close to the country's data; however the distribution of small/medium farmers (owning 1.00–4.00 acres) is less favourable in the sample area. On the other hand, concentration of large farmers (owning over 4 acres) is much higher in Satkhira than in the country as a whole.
The tenurial structure of the survey area also differs significantly from the findings of the Land Occupancy Survey (LOS). In the sample, land under owner-cultivator (75.5%) is much large than that of LOS (56%) and incidence of owner-cum-tenant farming is far lower (19%) than in that of LOS (44%). Farms under pure tenancy, however, occupy a large area in the sample (5.4%) than in the LOS (0.4%).
In Chakaria area the owned land is much lower than the access land, accounting for 38.6% and 61.4% of the total operated land respective. Tenurial structure in Chakaria area significantly differs from that of the Satkhira area and the country as a whole. Fifty six percent of the land of the country is operated by owner farmers, whereas in Chakaria that operate only 26%. The proportions of land cultivated by the owner-cum-tenant group and the tenant group are much higher viz, 59% and 15% respectively compared with 44% and 0.4% for the whole country.
In Satkhira area, only 24% of the land of owner-cum-tenant farmers is under paddy cultivation; the remaining 76% area is under shrimp culture. Similarly, 23% of tenant farmer's land is under paddy and the remaining 77% under shrimp culture.
Farmer's allocation of land to various uses reveals an interesting characteristic of Chakaria area. The highest proportion of land is allocated to crop-cum-shrimp-cum-salt cultivation (42.5%) followed by crop-cum-salt (20.9%), only salt (16.7%), and shrimp-cum-salt (11.4%), less than 10% is allocated to exclusive paddy (7.2%) and shrimp (1.3%).
Occupational Structure
In Satkhira area, 77% of the employed labour force is engaged in crop cultivation. They include a 10% segment having other minor occupations in addition to crop cultivation. Twenty one percent of the Labour force is engaged in non-farm occupations like business, services etc. Fishing is a relatively unimportant occupation engaging only 2%.
In Chakaria area, only 7% of the employed work force is engaged in crop cultivation, 31% and 40% engaged in crop and salt cultivation respectively, along with other activities; 6.4% employed in shrimp production. Business (7.7%), service (1.9%) and other occupations (5.8%) together absorb 15% of the employed labour force.
In Satkhira area nearly 6% of the male labour force is without employment. The highest incidence of unemployment is found among shrimp farmers (12.6%) and the lowest in the medium (1.00–4.00 acre farmer group (2.6%). Quantum of non-utilisation of available manpower, calculated on the basis of man-days available but not used, is 16%. Again the extent of non-utilisation is the highest among the shrimp farmers (20%), followed by the landless (18%) and the farmers of all size (15%).
The Chakaria area has about nine percent (3% higher than in Satkhira) of the total male labour force without work. The highest rate of unemploy ment is found among farmers owning than 4 acres of land (20%), followed by farmers owning 1 to 4 acres of land (17%), and crop/salt/shrimp farmers (7.9%). Man-days not used average 16% of the man-days available which is incidently same as incase of Satkhira.
Income and Profite
Incomes from different crops, salt and shrimp culture vary due to cost of production and unit sale price differentials. In Satkhira area, the total cost of production per acre for paddy cultivation has been estimated to be Tk.964.00, including cost of inputs (Tk.295.00) and wages (Tk.669.00). Netting out the cost, net return from T.aman cultivation on one acre of land comes to Tk. 1776.00 only. The fact that 63% of the total labour employed is family labour, it leads to retention of Tk.606.00 with the farming family. The net income accruing to the family is Tk.2382.00 which includes net return and the retained labour income. On the other hand, output from one acre of land under shrimp culture amounts to Tk.8390.00 with the cost of production estimated at Tk.4276.00. Netting out the cost, net return from shrimp culture on one acre of land comes to Tk.4114.00, which is 2.3 times higher than that of paddy.
In terms of employment generation paddy cultivation is more favourable than shrimp culture. For one acre of land paddy requires 63.3 mandays of labour whereas shrimp requires only 24 mandays. Based on this calculation, employment per acre of land under shrimp is 38% of that under paddy. The cost per work place in shrimp, however, is much higher than in paddy cultivation. But the relative share of wages out of the total net income is lower under shrimp culture than in paddy cultivation. In paddy, slightly less than one fourth of total income is paid out in wages while under the existing method of shrimp culture, it is only 15%.
In Chakaria area, four types of cultural practices are found : viz. paddy production only, salt production only, shrimp culture only an shrimp culture following salt production. The gross value of salt from one acre of exclusive salt cultural land amounts to Tk.7545.8. Netting out the cost of production (Tk.4466.1), the net return come to Tk.3079.8. Whereas the gross value of output from the land used for shrimp culture following salt production has been estimated to be Tk.13252.6. The estimated cost of production amounts to Tk.5863.8. Netting out the cost of production from gross value, net return amounts to Tk.7385.6. In case of shrimp culture only the gross value and cost of production have been estimated to be Tk.6160.00 and Tk.1277.0. The net profit accounts for Tk.4883.00. Paddy produces the lowest value of output and return, amounting to Tk.3208.00 and Tk.2427.00 respectively. Comparative productivity and profitability of the products and cultural practices shows that intensive land use practices producing shrimp culture following salt cultivation is very much encouraging in the area. Exclusive shrimp culture and crop cultivation under existing cultural practices is the weakest candidate for use of resources.
In terms of employment, salt-cum-shrimp has the highest generation capability and that also pays the highest wage rate on one acre of land. It employes 157 to 169 mondays of labour including 137 to 148 for salt cultivation and 20–21 for shrimp culture.
Next in the scale is paddy, which employes 65 mandays. The lowest is shrimp accounting for only 20–21 mandays. The income earned by labourers in salt production is 45%–47% higher than in case of exclusive paddy and shrimp.
CONCLUSIONS AND RECOMMENDATIONS
The survey area is typical of rural Bangladesh. Although its demographic and economic characteristics differ somewhat from the country as a whole, the deviations are minor. Introduction of shrimp cultivation in Satkhira area produces initial adverse effects on the subsistence economy. The level of employment is reduced; income accruing to the labourers declines in relative as well as absolute terms; income accruing to landlords (income from rent) and entrepreneurs tend to be the same group of people; their share increases while that of the agricultural labourers declines. With adoption of improved methods of cultivation, the absolute levels of income for all the groups increase, though the relative share of the labourers remains low and the income accruing to them grows at a much slower rate.
The adverse impact assumes a closed economy. A more accurate description of Bangladesh, however, would be an open economy. Because of the higher international price of shrimp, Bangladesh gains from increased production and export of shrimp. The expected gain from substitution of shrimp for paddy under the existing shrimp cultivation methods is ambivalent, but from improved cultivation method it is clearly very high. The higher international income would make augmenting cereals supply easier through import, thus raising the aggregate level of welfare. Though the income distribution becomes more skewed, the total income as well as absolute income of all groups rise.
The above analysis points to the need for a policy package including: expansion of shrimp cultivation; greater efficiency in shrimp production by adoption of improved methods; credit facilities for financing the required investment and higher working capital needs to meet operational cost; organization of marketing and storage facilities; extension services for dissemination of the knowledge of improved methods and related information etc.
The survey area is a typical. Its land allocation and utilization patterns show a high degree of diversification and modernization and shift away from subsistence agriculture towards commercial production.
The occupational structure shows considerable diversification. Though the occupations are all within the agriculture or rural sector broadly defined, dependence on any particular activity is minimal.
The Chakaria area occupies a unique position in the field of salt production in the country. Over ninety percent of the domestic salt production is done here. More importantly, climatological conditions make the place suitable for expension of modern salt industry based on solar evaporation process; and the vast tract of khas land permits establishment of salt farms of optimal/efficiency size. There is no other alternative location for salt industry with similar climatological and institutional advantages. Salt is not a usually traded item. So, the country must produce its own requirement.
In respect of employment generation, income distribution, and enhancement of wage income relatively as well as absolutely, salt production contributes much more than either shrimp culture or paddy. Public policy, therefore, should be directed towards encouragement of salt production in Chakaria and Cox's Bazar area and restriction of exclusive shrimp culture.
