PEOPLE'S REPUBLIC OF BANGLADESH
MINISTRY OF FISHERIES AND LIVESTOCK
FISHERIES RESEARCH INSTITUTE

BRACKISHWATER AQUACULTURE IN BANGLADESH: A REVIEW CONTENTS

DR. MAHMUDUL KARIM

FAO/UNDP TA-PROJECT BGD 83-010
IDA/WB AGRICULTURAL RESEARCH II PROJECT
REPORT NO 12, JANUARY 1986

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CONTENTS

SUMMARY

PREFACE AND AKNOWLEDGEMENTS

1 INTRODUCTION

2 CULTURE OPPORTUNITIES

2.1 Culture waters and area

2.2 Distribution of the culture area

2.3 Species for culture

2.4 Seed availability and collection

2.4.1 Species and numbers collected

2.4.2 Collection centres

2.4.3 Collection gear

2.4.4 Collection season

2.4.5 Seed sorting

2.4.6 Marketing and transportation

2.4.7 Seed price

3 FARMING PRACTICE

3.1 General farming pattern

3.2 Farm construction

3.3 Traditional culture techniques

3.4 Culture improvement

4 TECHNICAL PROBLEMS AND QUERIES

5 GOVERNMENT PLANS

6 BIBLIOGRAPHY

ANNEXES

TABLES

Table 1 - Distribution of shrimp farming areas over districts in Bangladesh

2 - Main collection centres for P. monodon seed

ANNEXES

Annex A - Distribution of shrimp farming areas

B - Changes in shrimp culture area over time

C - Percentage distribution of shrimp farms by districts

D - Shrimp farming areas by zilas and upazilas

E - Behundi jal (fixed bag net)

F - Mobile nets

G - Period of occurrence and abundance of selected fish and shrimp juveniles in Khulna region

H - Technical problems and queries

I - Public sector projects related to brackishwater aquaculture development and research

SUMMARY

1. Very rapid expansion of brackishwater shrimp farming has taken place in Bangladesh since the early seventies; this is particularly attributed to the incessant demand and increasing market price of shrimp in the world market. The Third Five Year Plan (1985– 90) has accorded high priority to brackishwater aquaculture in view of its vast potential for shrimp and fish production and rural employment.

2. By the beginning of 1986, brackishwater aquafarming covered an estimated area of 115,000 ha. This accounted for a 121 percent increase over the 1982 figure (52,000 ha).

3. Currently, over 78 percent (by area) of the shrimp farms is located in the Satkhira, Khulna and Bagerhat districts; the rest of the farms are in the Cox's Bazar area.

4. Brackishwater aquaculture alternating and/or simultaneous with transplanted Aman paddy cultivation is the general practice in the southwestern part of the country. In some parts in Cox's Bazar region aquaculture is rotated with salt production.

5. Penaeus monodon is by far the most important culture species. In many farms in the southwestern region, where the salinity is low for most part of the year, Macrobrachium rosenbergii is cultured together with paddy. Other important species that occur in the farms are P. indicus, Metapenaeus monoceros and M. brevicornis. Mullets are the most important brackishwater fish compatible with shrimp. During the paddy season, some freshwater carp species are also stocked.

6. Culture practice, until the beginning of the current decade was quite primitive with no or very little efforts for pond preparation, pest control, selective stocking, nursing, supplementary feeding and water management. The shrimp production rate was around 50 kg/ha of P. monodon per year. With the subsequent introduction of improved culture techniques through the combined efforts of the Government and some international agencies, there is an upward trend in the farm production and economic return. Currently, the P. monodon production rate is possibly 60–200 kg/ha.

7. Since selective or supplementary stocking of P. monodon postlarvae is becoming increasingly popular, the demand for stocking material has substantially increased. Hitherto shrimp culture depends entirely on the wild seed. Seed collection has developed into an expanding industry, employing many thousands of people (mostly teenager boys and girls). Sharp increase in the seed demand and the upward trend in the seed price warrant exploration and exploitation of new seed grounds on priority basis.

8. The farmers experience many technical problems during the culture proces. Technical queries are also made by the fishery officers connected with brackishwater aquaculture. A list of problems and queries frequently encountered is added to this report (Annex H).

9. The public sector activities to promote shrimp culture include demonstration, training and extension of improved culture techniques, establishment of new or upgrading of existing shrimp farms in the private sector, and establishment of shrimp hatcheries. A Brackishwater Fisheries Research Station (BFRS) particularly oriented to aquaculture is being established under the umbrella of the Fisheries Research Institute. A list of public sector projects devoted to brackishwater aquaculture is presented in Annex I, which also includes university research projects already carried out or under implementation.

PREFACE AND ACKNOWLEDGEMENTS

The Fisheries Research Institute of Bangladesh plans to establish a Brackishwater Fisheries Research Station under the IDA/WB Agricultural Research II Project. The FAO/UNDP, providing the technical assistance component for the above purpose, appointed a Soil Specialist (Dr. Mahmudul Karim) as a national consultant for five and a half months to recommend a suitable site for the Research Station. The consultancy started on 1 May 1986. His final report (FAO/UNDP TA Project BGD 83-010, Report No 11) on site selection was issued in November 1986. In fulfillment of the Consultant's Terms of Reference, the present report reviewing the current status of brackishwater aquaculture in Bangladesh, has also been prepared.

During the field studies, the following people were extremely helpful in establishing contacts with relevant persons:

• Mr. A.H.A. Jalil, Deputy Director of Fisheries, Khulna Division;
• Mr. Chatur Krishna, District Fishery Officer, Khulna;
• Mr. Jahaid Hossain, Upazila Fishery Officer, Paikgacha;
• Mr. Abdul Jalil, Chairman, Rampal Upazila;
• Mr. S.M. Babar Ali, Chairman, Paikgacha Upazila;
• Mr. Shahidul Islam, Deputy Commissioner, Satkhira.

Valuable technical information was received from the following persons:

• Mr. Ashraf Ali Shaikh, District Fishery Officer, Bagerhat;
• Mr. Rezaul Karim, Senior Scientific Officer, FAO/BOBP, Shrimp Culture Demonstration Farm, Satkhira;
• Mr. Abul Kashem, Project Officer, FAO/BOBP, Dhaka;
• Dr. Aftafuzzaman, medical practisoner and shrimp farmer (and ex-minister of fisheries), Satkhira;
• Mr. Habibur Rahman Khandker, Senior Scientific Officer, Shrimp Culture Demonstration Farm, Chakoria, DOF;
• Mr. Swapan Kumar, Scientific Officer, Marine Fisheries Research and Management Project, Cox's Bazar.

The Consultant expresses his indebtness to a large number of farmers who, when interviewed, patiently narrated their experience and supplied valuable field data.

Dr. J.C.J. van Zon, Teamleader of the FAO/Euroconsult consultant team for Fisheries Research Institute promptly provided all the necessary supports for smooth accomplishment of the consultancy work. He also made available to the Consultant several valuable reports relevant to brackishwater aquaculture development in Bangladesh.

The whole-hearted co-operation from the FRI Director, Dr. M. Asadur Rahman, is gratefully acknowledged.

(Mahmudul Karim)

INTRODUCTION

(01) Existing in a very rudimentary form for decades, brackishwater aquaculture in Bangladesh had been until recently nothing more than a casual activity in some tidal flood plain areas in the southwest part of the country.

(02) In the early seventies, Bangladesh entered the world export market for shrimp. This crustacean, which was locally cheap and not even accepted as food by many locals, suddenly became a very high priced commodity. Since then much attention has been focused on increased production of this crustacean. The public sector efforts concentrated on the exploitation of shrimp from the sea by operating trawlers. The increasing demand and steadily rising prices of shrimp also caused a silent revolution in the brackishwater aquafarming sector: what was merely a casual activity of little economic significance, emerged as a multimillion taka farming industry in a few years time. Increased by leaps and bound, the shrimp culture activities were spread over a 26,000 ha area by the beginning of the current decade.

(03) Surprising though, all this development took place in the private sector, without any extension, demonstration or new infrastructure support from the Government of Bangladesh. It is only since 1980, the starting year of the Second Five Year Plan, that brackishwater aquafarming has officially come to prominence.

In the Third Five Year Plan (1985–90) high priority has been given to brackishwater shrimp and fish culture. In view of the urgent socio-economic needs of the country (for domestic consumption, for export and for rural employment), the favourable ecological condition for shrimp culture and the existence of large areas with high production potential, this national priority for brackishwater aquafarming development is most justified. According to the Third Five Year Plan projection, brackishwater aquaculture will extend over 80,000 ha, as against 55,812 ha in 1984/85. By the end of the plan period, the production will expectedly increase to 34,000 MT, from a 1984/85 production of 9,000 MT. Nearly 18,000 MT of exportable shrimp would possibly come from aquaculture; this quantity would be 60 percent of the shrimp quantity projected for export in the terminal year of the Third Plan.

(04) The present shrimp farming area is reported to have already far exceeded the Third Five Year Plan target. At the beginning of 1986, shrimp culture activities spread over 115,000 ha, distributed over several coastal districts (Annex A). The production per unit area is, however, still rather low. The need for increase of the production rate by intensification of the culture methodologies is currently being emphasized. Thereabove, the farmers are facing a number of technical problems, that need systematic analysis and appropriate solution. The planned Brackishwater Fisheries Research Station (BFRS) under the Fisheries Research Institute will hopefully meet the research requirements for the brackishwater aquaculture sector of the country.

2. CULTURE OPPORTUNITIES

2.1 Culture waters and area

(05) Brackishwater aquaculture is mostly practiced in low-lying tidal flood plains within Water Development Board (WDB) polders, that were originally constructed to reclaim land with potential suitability for agriculture. In many areas, e.g. in Rampal and several other upazila's in Bagerhat District, the private farmers have constructed light dykes along the river banks for dual purpose of agriculture and aquaculture.

(06) Only those areas that are low enough to permit at least 50 cm of inundation by spring tides throughout most of the year, are normally used for shrimp culture. Excavation of land for construction of brackishwater shrimp farms is not in practice in Bangladesh. Pumping, to supply water from the surface or from sub-surface layers, is also not used for aquafarming.

(07) In some places (quite common in Paikgacha, Rampal, Pirojpur, Patuakhali, and elsewhere) many small domestic ponds are connected with tidal creeks; these ponds are used not only for domestic washing, but also for shrimp and fish culture with various degrees of intensity.

(08) A survey conducted by the Directorate of Fisheries (DOF) revealed that in 1982/83 there were 52,000 ha of shrimp farms in Bangladesh. The shrimp culture activities quickly expanded, and by 1984/85 total farming area was estimated at 70,000 ha (Aquatic Farms Ltd., Hawaii, USA, engaged by the Asian Development Bank for Bangladesh). The latest estimates, made by DOF officers located in the coastal districts and currently officially used by the Directorate of Fisheries, indicate that in the beginning of 1986, the shrimp culture area exceeded 115,000 ha.

2.2 Distribution of the culture area

(09) The distribution of the shrimp farming areas over districts in 1982/83, 1984/85 and January 1986 is summarized in Table 1. The most spectacular increase in farming area took place in the Khulna District, recording a 272 percent increase in January 1986 over 1982/83.

(10) The changes in the culture area with time are graphically presented in Annex B. The percentage distribution of the shrimp farms by district and time is given in Annex C. According to the latest estimates, (January 1986), the percentages of the total farming area covered by the Districts of Satkhira, Khulna, Bagerhat and Cox's Bazar are respectively 14.5, 41.3, 23.0 and 29.8. In the same year, the southeast zone of the country comprised over 79 percent of the total shrimp farming area; the remaining 21 percent laid wholly in the Cox's Bazar District of the southeast zone.

(11) An overview of the culture area and of the number of farms per upazila is presented in Annex D.

Table 1 - Distribution of shrimp farming areas over districts in Bangladesh

(1) Others: Jessore, Bhola

2.3 Species for culture

(12) Several species of shrimp, crab and fish may naturally occur in the brackishwater aquafarms. Only two genera of shrimp, Penaeus (mainly P. monodon) and Macrobrachium (mainly M. rosenbergii) are deliberately stocked in the farm ponds. P. monodon is by far the most desired culture species. M. rosenbergii is stocked only in areas of low salinity. Although spawning and larval development of M. rosenbergii occur in the brackishwater region (10–15 ppt salinity), its further development normally takes place in freshwater. The species may also grow well in waters of low salinity.

(13) Metapenaeus monoceros, a rather small sized shrimp, is a welcome intruder because of its export quality; the species abundantly occurs in nature. P. indicus and P. merguensis occur in small quantities in the southwest zone of Bangladesh. They are also welcome in the farms; the two species may grow to a fairly large size and are well exportable. Metapenaeus brevicornis, a small shrimp, makes up a substantial contribution to the total production. This species was more or less considered a pest in the culture systems, but it has, of late, entered the export market to a limited extent.

(14) Amongst the fin fishes, mullets Liza and/or Mugil spp.) are the most desired genera; they are autostocked. The young ones of these fishes are occasionally collected from the wild and stocked along with shrimp.

During the low-saline period, starting with the onset of the monsoon, some farmers stock freshwater carp (Bangladeshi and Chinese species) and/or tilapia (Oreochromis nilotica, O. mossambica).

The most bothersome species of fish occurring in the culture systems include a number of predators, e.g., Lates calcarifer, Eleutheronema tetradactylum, Glossogobius giuris, and Mystus menoda. Mudskippers are also quite common. Congresox eels occur occasionally. Except for the eels, all other predator fish have high demand and command a good price in the local markets, but they can decrease the shrimp harvest substantially.

2.4 Seed availability and collection

2.4.1 Species and numbers collected

(15) Shrimp farming in Bangladesh still entirely depends on natural seed supply. P. monodon is the only salt water shrimp of which postlarvae are collected on commercial scale for stocking. It is estimated that the number of P. monodon postlarvae collected in 1985 was in the order of 1–3 billion.

M. rosenbergii postlarvae and juveniles are collected in the Khulna region for stocking in freshwater ponds or in low salinity brackishwater shrimp farms. No estimates are available of the number of M. rosenbergii seed collected annually.

Collection of mullet seed seems to be an occasional practice in the Satkhira and Khulna districts.

2.4.2 Collection centres

(16) The main collection centres for P. monodon seed are shown in Table 2. There are apparently vast areas in the mangrove forests, supposedly rich in seed supply, that are still lying completely unexploited.

2.4.3 Collection gear

(17) Basically two types of seed collection gear are encountered: fixed and mobile. The fixed type is a bag net, locally called Behundi jal (Annex E). The net is made of a synthetic material called velon. The screen has a P-24 quality (24 meshes per 2.5 cm lenght). About 15 m2 material is needed for one net; two guide wings require extra material of the same quality. The cod end is generally made of second-hand synthetic cloth. The net is fixed near the shore with a bamboo pole and can be operated from the shore.

Table 2 - Main collection centres for P. monodon

The mobile nets may be triangular or rectangular. They are made of bamboo or mangrove twig frames and P-24 velon screen (Annex F). The gear is operated either by pushing or pulling.

(18) There is a clear scope for improvement of the existing seed collection gears to achieve more effective seed collection under varied environmental conditions, such as on the open sea beach, in tidal areas with mangrove bushes, in rivers with strong currents or floating trash, on the tidal flats, etc.

2.4.4 Collection season

(19) The seed collectors report that P. monodon seed occurs in the main collection centres throughout the year. In the Khulna region, the period February-May represents the peak seed collection as well as pond stocking season. Later in the year the seed demand declines, since there will be not much time for stocked shrimp to grow to good grades before the monsoon starts freshening the pond and river waters. In the Cox's Bazar region the peak seed collection period is April-June.

(20) M. rosenbergii postlarvae are reported to be available in the Khulna region from April. Its demand peaks in July, when most of the P. monodon is generally harvested, the water salinity drops and the large farms are ready for stocking freshwater species. The periods of occurrence and abundance of selected shrimp and fish fry are presented in Annex G.

2.4.5 Seed sorting

(21) The seed collectors transfer their catch along with floating mangrove twigs, leaves, etc. to earthen bowls. A group of small children spreads the collection along with water in white enamelled flat plates and sorts out the P. monodon seed with plastic spoons or freshwater mussel shells, and throws away the rest of the shrimp postlarvae and fish fry on the shore. This leads to a collossal damage to the shrimp and fish resources every year.

(22) Detailed quantitative and qualitative analyses of the collections made during the seed collection efforts have never been attempted. Rough observations during field visits suggested, that P. monodon postlarvae constitute at the most one percent of the total collection; larvae and postlarvae of miscellaneous shrimp, crabs, mysids, fish, etc., make up the rest. If one percent of the collection counts 1–3 billion (estimated number of P. monodon postlarvae collected from the wild), the remaining 99 percent would count about 99–297 billion animals. This is an enormous number of organisms, having the potential of producing a large quantity of much needed animal protein for human consumption.

2.4.6 Marketing and transportation

(23) The seed collectors normally sell their seed to the seed traders. The seed normally passes through a few tiers of middlemen before it reaches the farms. At every change of hand, the seed price obviously goes up. Head-loading, country boats, motorized boats, rickshaw, vans, bicycles and buses are employed for seed transportation. Alluminum vessels of 20–30 litre capacity are the most popular containers for long distance transportation. The water in the container is changed a few times, if the transporter considers it necessary or finds it feasible. The temperature and the salinity of the changed water often widely differ from those of the original container water. The seed transporters sometimes put table salt into the container water with the belief that it will keep the seed healthy and strong. Estimates of seed mortality during transportation vary from 10–50 percent but it could well be higher: no experimental data on seed mortality are available.

2.4.7 Seed price

(24) During the last six years, the P. monodon seed price has gone up from Tk 40–50 in 1980 to Tk 400–600 per thousand postlarvae of about 15 mm size in 1986. The maximum price of the seed coincides with the peak stocking season, which in the Khulna region is February-May. Just before the monsoon and during the low saline months, P. monodon culture is limited only to a few high saline areas in Shyamnagar; the P. monodon seed then sells at a very low price. (Tk 30/1000). The off-season price of P. monodon seed drops to as low as Tk 10–15/1000 in cox's Bazar area.

(25) The price of M. rosenbergii seed (25–50 mm) currently ranges from Tk 500–1000 per thousand in Satkhira area; The same quality seed sells at about half the price in Paikgacha area.

Mullet seed (20 mm), if at all available, sells at Tk 200 per thousand in Satkhira area, while in Paikgacha area, the species commands only one-fourth of the above rate.

3. FARMING PRACTICE

3.1 General farming pattern

(26) Combination of aquaculture with agriculture is the normal parctice in the southwest zone. The farming pattern basically is as follows:

During the high salinity period (January-July):

• culture of marine and brackishwater shrimp and fish and harvesting of the marketable individuals.

During the low salinity period (August-December):

• continuation of rearing of the undergrown shrimp and fish of euryhaline nature in the low-lying areas and ditches in the fields;
• culture of freshwater fish and shrimp together with the euryhaline brackishwater species;
• cultivation of a slightly salt-resistant transplanted Aman paddy in the elevated parts of the fields;
• harvesting of the residual shrimp and fish.

(27) Most of the shrimp culture activities are carried out in large dyked areas, called polders. They are locally known as Ghers, meaning earthen enclosures. The dyked brackishwater region is suitable normally for one crop of transplanted Aman paddy during August-December, when the water and soil salinities are low. Agricultural crop production during January-July is difficult. The increase of the salt content of the top soil in the dry season caused by capillary rise of the saline ground water, limits the possibilities for cultivation of a second crop. Freshwater for irrigation is not available since both surface water and ground water are saline during the dry months.

There is still another problem: the soil is acidic in many places. When exposed to the sun, the soil acidity increases further, reducing soil productivity.

(28) Instead of keeping the land fallow during the high salinity period, many farmers find it rather profitable to utilize the low-lying and adequately submersible lands for fish and shrimp farming. Thus, many tidal flood plains are used for agriculture during the wet months and aquaculture during the dry months (rotation).

3.2 Farm construction

(29) Using individual small plots for aquafarming is presently technically not feasible. The well-to-do farmers, either individually or in groups, take a large number of contiguous plots (large and small) within a WDB polder on one to a few years' lease from the land owners.

(30) Various farmer groups construct sub-dykes, separating their farms. Each farm has its own water inlet and outlet, mostly by wooden structures. In Cox's Bazar area, reinforced cement concrete (RCC) pipes are also used. The WDB dykes are cut open and the wooden sluices are placed in the cuts to take in or drain out water from or to adjacent canals. The inlet sluices are placed at a level higher than the ground level; outlets are placed at the ground level. Sluices of various specifications are encountered, but average dimensions are 45×45×1200 cm. The planks are about 2.5 cm thick. They are mostly of unseasoned and untreated wood of Sundari' Garjan, mango, blackberry, and others. The most common range of the diameter of RCC pipes used is 22–30 cm. No engineering devices are adopted to arrest water leakage around the sluice structures or the shutter boards.

3.3 Traditional culture techniques

(31) By mid-December, cropping of paddy is normally completed. Harvesting of finfish and any residual stock of marine shrimp is also completed. Macrobrachium rosenbergii (if stocked at all) may still grow on to a sufficiently large size; the farmers would therefore prefer this shrimp to remain in the field. This can be done if there are suitable ditches or canals that can be used as sanctuaries. The field itself, along with the paddy stumps, is normally exposed to the sun until the beginning of February. Then the P. monodon seed appears in good numbers and the spring tides are high enough to adequately inundate the field. The total period of field drying varies from farm to farm and from place to place.

(32) Until recently, no screens were used in the sluice structures to prevent entry of predator animals into the farm. Screens to prevent escape of the autostocked animals were also not used, based on the belief that autostocked animals (and particularly P. monodon shrimp) would not leave the farm with the outgoing tide water before they have grown to a large size. Sometimes farmers did use coarse bamboo screens in the drainage sluices to retain the stock, but the screens were too course to serve the purpose effectively.

(33) Selective stocking was unknown until rather recently. A few farmers started practizing supplementary stocking with P. monodon and M. rosenbergii postlarvae or juveniles. Seed collection was limited to Satkhira and Kaliganj areas. A nursery prctice was not followed. The concept of the need of liming, fertilization and artificial feeding to enhance shrimp production was still to be introduced. Unaware of the ecological needs of the shrimp, the farmers' concern was only to facilitate entry of as many shrimp seed as possible into the farm, and not to maintain the required physico-chemical qualities of the water.

(34) By using these traditional methods, with no or very little efforts for pond preparation, liming, fertilization, pest control, selective stocking, nursing, supplementary feeding, and water management, the shrimp production rate was low, probably not exceeding 50 kg/ha of P. monodon per year.

3.4 Culture improvement

(35) From the early eighties, the Government of Bangladesh has been taking definite efforts to improve the traditional culture practices. With the help of an FAO/SIDA assisted demonstration farm located at Satkhira, and through a series of training courses also assisted by FAO, the Government has introduced a number of improved culture techniques.

(36) Technologies most visibly transferred to the farmers level during the last few years are:

• Nursery rearing of postlarval shrimp to juveniles before stocking them into large grow-out ponds. A part of the Gher is separated by a low and narrow dyke, and this area is used as a nursery pond. Water is passed through fine-mesh synthetic screens to check unwanted animals. Some farmers undertake pre-stocking pond prepartion by ploughing and application of cow dung. Some farmers resort also to supplemental feeding of the postlarvae;
• Screening of the grow-out pond sluices with closely spaced bamboo splits, with imported synthetic netting, or with a combination of both, to prevent/reduce intrusions of predator and competitior organisms;
• selective stocking with P. monodon postlarvae collected from various rivers. Most farmers, however, still allow autostocking of P. monodon (obviously, along with a heterogenous mixture of other shrimp and fish). They do so when some of the most destructive predator fishes do not occur or show a minimal presence in the supply river.

(37) The Government demonstration and extension efforts have also evinced good interest amongst many farmers in pre-stocking pond preparations, including ploughing, liming, manuring and chemical fertilization. In fact, many progressive farmers have already started using some of these production inputs. However, their use is often haphazard, and not on any scientific base. This often leads to inappropriate application of the expensive inputs. One example can be cited here: during the consultant's field visit in Paikgacha, an enthusistic farmer was taking all measures to deep-plough his field with a tractor, hoping that deep ploughing would greatly enhance the farm's productivity. According to the soil survey report of the Soil Resources Development Institute, the farm was located in an acid-sulphate area. The possible risk of exposing the acid-loaden sub-surface soil was explained to him. The farmer thereafter changed his plan.

(38) During the consultancy period, a limited survey of the use of production inputs was conducted. The quantity of cow dung, if used at all, was reported to vary from a few kilogram to 90 kg/ha. The rate of lime application was 2–10 kg/ha, and that of TSP and urea was each 0.5–10 kg/ha. It was not possible to correlate the use of the above imputs at the stated rates with the aquatic production, but it was clear that the farmers were very responsive to new technologies. The farmers also appeared to have realized the need of better pond and sluice designs and construction, of better water management and of supplementary feeding. They understand often the “why” of this measures, but they did not know the “how”.

(39) Adoption of improved techniques was found to be more common in the Satkhira district than elsewhere in the country. The recent production rate of P. monodon in Satkhira area is reported to be 65–250 kg/ha, which is also higher than elsewhere. In 1985, the FAO assisted shrimp culture demonstation project at Satkhira produced 81– 212 kg/ha of P. monodon. Adding all other shrimp and fish harvested, the production was 260–549 kg/ha, with an average of 428 kg/ha. One of the private farms just across the Bagkhali river in Cox's Bazar reported an average production of 370 kg/ha of P. monodon while a well managed one hectare pond produced nearly 1.5 t/ha.

TECHNICAL PROBLEMS AND QUERIES

(40) During the reconnaissance survey work in various shrimp farming areas, the consultant took the opportunity of interviewing many shrimp farmers to find out what kind of technical problems they normally face. Discussions were also held with the fishery officers located in the coastal zilas and upazilas, to assess the technical problems encountered and to collect the queries frequently made by the local shrimp farmers. Based on this field information and individuals' views, coupled with the consultant's own practical experience gathered in the past *), a list of problems and queries has been prepared under 11 heads (annex H).

(41) It is hoped that the Fisheries Research Institute will find the questionnaire provided in Annex H helpful in prioritizing its applied research activities in its Brackishwater Fisheries Research Station (BFRS), to be constructed in 1987 in Paikgacha.

*) The consultant, as FAO/Bay of Bengal Programme Aquaculturist, had been associated with the implementation and monitoring of a shrimp culture demonstration project at Satkhira from 1981–85.

5. GOVERNMENT PLANS

(42) The Government of Bangladesh has attached high priority to brackishwater aquaculture. Eight of the projects included in the Third Five Year Plan are either wholly devoted to brackishwater aquaculture development, or have specific components that are relevant to brackishwater aquaculture development or research. The Third Five Year Plan outlay for the fisheries sector is Tk 3,500 million of which an approximate amount of Tk 2,500 million will be spent for aquaculture development and research. The share of the brackishwater sector will be around Tk 1,400 million; this represents 40 perent of the total financial outlay for the entire fisheries sector and 56 percent of the allocations earmarked for aquaculture development and research. A list of the relevant projects with the plan allocations, approval status and the co-operating agencies is presented in Annex I; the project purpose, as far as relevant to brackishwater aquaculture only, has been highlighted below the name of the project.

(43) Brackishwater aquaculture research projects already implemented or under implementation at various universities are also listed in Annex I.

6. BIBLIOGRAPHY

Anon., 1979
Draft final report, Annex-B. Proposed fisheries components for an agricultural credit project. Agricultural Credit Studies Project, prepared by Nathan Associates, USA for Bangladesh Bank, Dhaka.

Anon., 1984
National Water Plan Project. Second Interim Report, Vol. VII-Fisheries. Master Plan Organization, Ministry of Water Development & Flood Control, Bangladesh. Prepared by Harza Engineering Company International.

Anon., 1984
Bangladesh coastal aquaculture project engineering study - Draft Report, Vol. I. Prepared by Development Consultancy Services Ltd. and Engineering Consultancy Services & Associated Ltd., Dhaka for the World Bank.

Anon., 1985
Shrimp culture in the semi-saline zone of the Delta. Delta Development Project (BWDB), Technical Report No 13, Vol I, 60 Pp., Arnhem, Haque.

Anon., 1985
Shrimp culture in the semi-saline zone of the Delta. Delta Development Project (BWDB), Technical Report No 13, Vol. II, 102 Pp, Arnhem, Haque.

Anon., 1985
Report on tidal area study. Draft report prepared by Development Consultancy Services Ltd. and Engineering Consultancy Services Ltd., Dhaka for FAO/UN.

Anon., 1985
List of projects for the Third Five Year Plan, Planning Commission, Govt. of Bangladesh.

Anon., 1985
Report on engineering study (Vol. I) - Bangladesh coastal aquaculture project (World Bank). Prepared by Development Consultancy Services Ltd. & Engineering Consultancy Services Ltd., Dhaka.

Anon., 1986
Bangladesh Second Aquaculture Development Project preparation report. Prepared by Aquatic Farms Ltd., Hawaii, USA for the Government of Bangladesh and the Asian Development Bank.

Anon., 1986
Draft feasibility report on package-1, Khulna Coastal Embankment Rehabilitation Project TA No 665-Ban, Vol. I. Prepared by Agricultural Development Corporation (ADC), Seol Korea in association with Associated Consulting Engineer (Bangladesh) Ltd.

Anon., 1986
ibid, vol III.

Ali, M. Liaquat, 1983
Shrimp farm survey in coastal area of Bangladesh, Dhaka (mimeo).

Chowdhury, A.Q., 1986
Fishermen community and development of closed water fishery in Bangladesh.

Funegaard, P., 1986
Shrimp seed - any to sell? Come to Satkhira, Bangladesh. FAO Bay of Bengal News, Issue No 22.

Karim, M., 1986
Site selection for the Brackishwater Fisheries Research Station (BFRS), FAO/UNDP TA-project BDG 83-010, Report No 11, 44 Pp.

Karim, M., 1986
Integrated farming of shrimp, fish, paddy and goat at Satkhira. FAO/BOBP/Rep. Madras, India.

Kibria, C., 1983
Prawn and shrimp resources of Bangladesh, Dhaka (Mimeo).

Mahmood, N., 1986
Effects of shrimp farming and other impacts on mangroves of Bangladesh. Paper presented at the Third Session of IPFC Workshop on Inland Fish/Mangrove, 22–25 June, Bangkok, Thailand.

Majumder, M.R., 1983
Shrimp culture status and extent in Cox's Bazar area, Dhaka (mimeo).

Marr, J.C. associates, 1985
Twenty year fishery development plan for Bangladesh. FAO/UNDP.

Smith, W.G., 1982
The tidal area study - a preliminary report. FAO/UNDP Fisheries Resources Survey System, Dhaka (mimeo).

Smith, W.G., 1982
The tidal area study - a preliminary report FAO/UNDP Fisheries Resources Survey System, Dhaka (mimeo).

ANNEXES

ANNEX A
DISTRIBUTION OF SHRIMP FARMING AREAS

ANNEX B
CHANGES IN SHRIMP CULTURE AREA OVER TIME

ANNEX C
PERCENTAGE DISTRIBUTION OF SHRIMP FARMS BY DISTRICTS

1982/83
1984/85
Jan. 1986
K= Khulan B= Bagerhat S= Satkhira C= Cox's Bazar

ANNEX D
SHRIMP FARMING AREAS BY ZILAS AND UPAZILAS

* Brackishwater aquaculture in Bhola is very crude and mostly consists of just sheltering the wild shrimp and fish of heterogenous species in the defunct courses of rivers and canals. There are opinions that the process cannot be called aquaculture.

** Data not available

ANNEX E
BEHUNDI JAL (FIXED BAG NET)

ANNEX F
MOBILE NETS

ANNEX G
PERIOD OF OCCURENCE AND ABUNDANCE OF SELECTED FISH AND SHRIMP JUVENILES
IN KHULNA REGION

ANNEX H
TECHNICAL PROBLEMS AND QUERIES

A. Farm construction

01 What practical measures are recommended to prevent or reduce erosion of the pond dykes?

02 What structural improvements in the traditional sluice boxes should be provided to check excessive water leakage through or around the water control structure?

03 What should be the architectural design of a pond and the associated structures for intensive culture of P. monodon? M. rosenbergii?

04 What type of structural design is suggested to ensure reasonable water circulation in large ghers?

05 What should be an ideal design for a shrimp nursery pond?

06 How can the pest control screens be made most effictive without drastically interfering with the water flow through them?

07 Is there any mechanism for automatic cleaning of the pest control screens?

B. Seed

01 During the new moon and full moon periods, there are heavy incursions of P. monodon postlarvae on or near the Cox's Bazar sea beach. What technnique is most effictive for collecting the postlarvae on a large scale?

02 Where are the new prospective seed grounds for P. monodon and other culturable marine shrimp and finfish?

03 Where are the best places for gathering M. rosenbergii postlarvae and juveniles?

04 What methods are suggested to attract the postlarvae of P. monodon, M. rosenbergii and other shrimp species in a river or a mangrove creek to make the seed collection efforts more rewarding?

05 What gear is recommended for mass collection of advanced P. monodon, M. rosenbergii postlarvae, which are benthic in habit?

06 What are places where P. monodon postlarvae are available in large quantities throughout the year?

07 When do P. monodon postlarvae occur in larger quantities - at day time or night time? During low tides or high tides?

08 What are the most satisfactory methods to quickly sort out the P. monodon, P. indicus and M. rosenbergii postlarvae from heterogenous collections?

09 How to quickly identify the culturable shrimp seed and mullet fry in a live field collection?

10 What arrangements are recommended for bulk transportation of the shrimp seed over long distances?

11 Is it feasible to carry M. rosenbergii seed for commercial culture of this shrimp to the northern districts of the country?

12 In case of non-availability of artificial oxygen facilities (e.g. oxygen cylinder, oxygen bags, etc.), what measures are recommended for long distance transportation of the shrimp seed?

C. Nursing

01 What would be the most practical way to acclimatize the shrimp and fish fry in the pond environment before stocking them into the pond?

02 What salinity range would be suitable for P. monodon nursing?

03 What kind of shelters and substrata would be locally suitable for P. monodon nursery ponds?

04 How to control the predatory fish in a nursery pond that cannot be immediately dried?

05 How to stimulate growth of natural food organisms in a shrimp nursery pond?

06 What kind of water management is recommended in shrimp nursing?

07 What kinds, quantities and methods of artificial feeding are recommended for shrimp fry?

08 How can nursing be best parcticed in a situation where a nursery pond does not exist or cannot be created?

09 What should be the stocking density in a nursery pond?

10 How to quickly gather juvenile shrimp for transfer from a nursery pond to a juvenile growing pond?

11 What techniques are recommended to transfer the juveniles from a nursery pond to an isolated grow-out pond in a pond complex?

D. Field preparation

01 In some farms, though the field is thoroughly ploughed, exposed to the sun for a long time, and fertilized, the growth and production of shrimp are not satisfactory. On the other hand, some nearby farms not ploughed, not thoroughly dried, and not fertilized generally produce better crops. What could be the reasons?

02 In some dug-out ponds, the shrimp either suffer heavy mortality or demonstrate poor growth. What could be the possible reasons for this and how to solve the problem?

03 How to determine the requirements of lime and fertilizers for a shrimp farm?

04 Cow dung in large quantities is unlikely to be available for manuring shrimp farms. What alternatives can be used under Bangladesh conditions?

E. Water supply and management

01 Would it be technically and economically feasible to use underground water (fresh or saline) either to raise or to dilute the water in a culture pond?

02 Would it be economically feasible to use a pump for supplying water to a brackishwater aquaculture farm?

03 Is it advisable to use table salt or dehydrated sea water salt in shrimp ponds to stabilize pond salinity when the pond water tends to get freshened due to rains?

04 What should be the water management techniques for fertilized ponds?

05 How often and how much water should be changed from the farm?

06 What precautions should be taken to save the shrimp from the deleterious effects of sudden salinity drop due to heavy rains?

07 What depth of water is recommended for a nursery pond and a grow out pond for shrimp?

F. Feed

01 What food and how much food should be used for P. monodon and M. rosenbergii farming?

02 How to prepare formulated dry feed and how to store it for several months under rural conditions?

03 What local ingredients would be most suitable for formulated dry feed preparation? What would be the cheapest but most effective water-stable binding material?

G. New culture species

01 P. indicus seed occurs in Cox's Bazar area in far greater number than that of P. monodon. Is it possible to culture P. indicus on sufficiently profitable basis in Bangladesh?

02 While P. indicus has a higher or at least the same price as P. monodon in the international market, why the former species receives only half the price of the latter in Bangladesh?

03 How big does P. indicus grow in ghers? What is their rate of growth at different stages?

04 What do mullets and Scatophagus eat in nature?

05 Metapenaeus brevicorcis is a prolific species of small size and is regarded as a pest in the shrimp farms. Shrimp of similar size sells at quite high price in many foreign countries. Is it possible to suitably process the small shrimp and promote its export at a sufficiently lucrative price?

H. Pests

01 What kind of pest control mechanisms would be effective at the inlet sluice of single unit shrimp ghers of large size, as common in Bangladesh?

02 What techniques could be adopted to remove fairly large size predator fish (Lates, Eleutheronema, Glossogibius and Mystus) from a shrimp farm?

03 What techniques could be employed to concentrate the metapenaeid shrimp and crabs and remove them from a P. monodon pond?

04 Is it good to have lots of floating filamentous algae and/or rooted vegetation in the pond? If not how to control them?

05 How to check avian predation particularly of P. monodon postlarvae which, by habit, cling to the pond peripheral vegetation?

06 How to handle crab hole and rat hole problems in the dykes?

I. Pathological problems

01 Sometimes, large populations of the shrimp in culture fields have soft shells and spongy muscles. After harvest, the animals quickly loose their body fluid and weight. What are the preventive and curative measures for this problem?

02 The body surface of the shrimp or crab is often covered with a patch of whitish slimy coat. What is this due to? Does this cause any pathological problems to the animals? If so, how to treat or avoid it?

J. Environmental factors

01 What are the salinity minima for P. monodon and P. indicus survival and growth? What is the salinity range most ideal for best survival and best growth of the two above mentioned species?

02 Is the winter temperature of water in Bangladesh too cold for the culturable shrimp? What precautions should be taken to ensure good survival of the shrimp (postlarvae and adult) during the winter months?

03 What could the farmers do to guard the shrimp for any possible environmental stress during a period of continuous rainfall, or during a prolonged period of cloudiness and drizzling?

04 How can artificial aeration be provided (mechanically and manually) in an intensive or semi-intensive culture pond (either for nursing or for grow-out)?

05 What are the maximum salinity levels at which Catla catla, Labeo rohita, Cirrhina mrigala, Hypophthalmichthys molitrix, Oreochromis nilotica, O. mossambica and Ctenopharyngodon idella survive and grow normally?

06 Does frequent water exchange create any siltation problems in the canals and fields inside the polder? If so, what measures should be taken to counter the problem?

K. Harvesting

01 Is it possible to prevent the undersized P. monodon from being undesirably trapped or bag-netted while harvesting the marketable individuals? If so, how?

02 How to carry out partial and complete harvesting of a pond with submerged mangrove plants or their remnants?

03 Large crabs with strong chaelepeds often cause heavy damage to the high priced shrimp and fish caught in a trap. How to prevent the crabs from entering the traps (Dhosna)?

ANNEX I
PUBLIC SECTOR PROJECTS RELATED TO BRACKISHWATER AQUACULTURE DEVELOPMENT AND RESEARCH

* A Estimated cost (in million Taka)
B TFYP allocation at 1984/85 prices (in million Taka)
C Estimated share of brackishwater fisheries development & research (in million Taka)
D Implementing agancy
E External agencies involved/may be involved in brackishwater component

** The brackishwater component or the financial allocation indicated thereto is not reflected in the List of Projects for the Third Five Year Plan for the fisheries sector