Aquaculture practices in mangrove area.
- 1. INTRODUCTION 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. 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. 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. 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.
- 3. Culture waters and area 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. 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. Species forculture 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. 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. 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. FARMING PRACTICE 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. 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
- 4. 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. Figure: Farming practice in mangrove area Traditional culture techniques 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
- 5. 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. 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. 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. 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.
- 6. As per adoption of managerial practices we may visualize following types of culture in Bangladesh which includes Sundarbans to a) Traditional b) Extensive c) Semi‐intensive d) Intensive e) Paddy cum fish culture f) Bhasabada fisheries Monoculture of shrimp in aqua farm is discouraged as this significantly increases the risk of disease outbreak. Traditionally, polyculture practice is encouraged. However there are some issues which have negative impact on aquaculture and fisheries sec tor. These are: Two types of stocking/harvesting regimes exist Multiple (continuous) stocking/multiple (continuous) harvesting: Single stocking/single harvesing The main fish species currently cultured in the Sundarbans areas 1. Bagda chingri (Tiger shrimp) 2. Golda chingri (Giant freshwater prawn) 3. Parsia (mullet, Liza parsia) 4. Bhangan (mullet, Mugil cephalus) 5. Magur (walking catfish, Clarias batrachus) 6. Tengra catfish 7. Catla 8. Rohu 9. Silver carp 10. Tilapia 11. Guppy (ornamental fish) 12. Molly (ornamental fish) 13. Swordtail (ornamental fish) Several species opportunistically enter shrimp ponds, and are harvested and sold as ‘bycatch’ 1. Bhetki (sea bass) 2. Scatophagus argus 3. Milkfish 4. Baila (goby) 5. Therapon (Therapon perch) 6. Besides Crabs form an important crop here The ultimate objectives of aquaculture sector development area 1. To increase the income and employment of the population 2. Raise the nutritional status 3. Maximize economic returns from unit water area 4. Increase the availability of fish in domestic market at reasonable price and 5. To enhance the foreign exchange earnings.
- 7. Major problems in the shrimp farming sector are as follows: 1. Pond leases 2. Water supply 3. Feed quality and supply 4. Diseases 5. Finance system tied to monopoly purchase rights 6. Chain of traders 7. Icing shrimp 8. Shortage of raw material for processing 9. Unplanned development Steps taken for extension / Diversification of aquaculture: 1. Under Extension programme continuance of the Central Sector Scheme viz. Statistical Survey is necessary during the 10th Five Year Plan period. 2. Setting up of regional branches of C.I.F.T/C.I.B.A/National Institute of Cold Water Fishery/National Bureau of Fish Genetic Resources/C.M.F.R.I in WB 3. R & D efforts for genetic management for fish should be immediately started because the resources of sea are not unlimited. 4. Import of parent stock (brood fish) in the ornamental fishery sector. 5. Waving of Import Duty on Artemia for prawn & shrimp hatchery and Ovaprim (ind ucing agent) in fin fish hatchery. 6. Setting up of modern fish feed industry with high FCR value. 7. As exploitation of sea resources has almost reached optimum level in inshore fishing, it is an immediate necessity to start cultural operations in respect of Mudcrab, Seaweed, A lgae (spirulina), Catfish, Oysters etc. 8. Transfer of technology for Seabass breeding. Steps those are necessary for Sustainable Aquaculture: 1. Farm registration with Aquaculture Authority 2. Optimizing input use (feed, fertilizers etc.) 3. Avoiding usage of antibiotics 4. Monitoring residue in farm products 5. Appropriate disease management 6. Water quality management (both inlet & outlet) 7. Farm hygiene maintenance and post harvest handling 8. Trainingto farmers on GAP
- 8. Major problems faced by shrimp aquaculture sector are as follows: 1. Pond leases: Lease period for ponds and bheris are between one and three years durat ion. This is too short a time for longer term investments, and there is no incentive for shrimp farmers to improve the infrastructure of the pond, let alone drain the pond and prepare the substrate properly. The regulation for shrimp pond leasing need to be standardized, and lon ger lease term specified. Fivee year or more is desirable. 2. Water supply: The water supply is not properly designed in may areas. In some cases, the outflow from one pond forms the inflow to an adjacent pond. Pollution of the water s upply is also a problem. Organic sludge settles on the pond bottom and requires removal. A eration is needed to break down the BODs. The nutrients initially result in good phytoplank ton growth in February which is beneficial to shrimp and mullet growth. However, by April cloudy weather sets in, resulting in dying and decomposition of the phytoplankton and low er water quality. Disease outbreaks sometimes begin as a result. 3. Feed quality and supply: Feed is considered the second most important issue for the s hrimp farming industry. The supply of shrimp and fish pellet feed is a problem. In lieu of a dequate quality feed supply, farmers are forced to use local feed materials, and these do not also result in maximal growth. 4. Diseases: The production of shrimp from farms is threatened by white spot and other diseases. Shrimp are said to be most prone to disease outbreak in July‐ August during the monsoon (possibly due to the abrupt change in salinity in ponds). Mortal ity is heaviest under monoculture, and less under polyculture. Previously, higher stocking d ensities were used (3,000 PL per ha) but this resulted in frequently disease outbreaks. 5. Finance system tied to monopoly purchase rights: Adequate finance for shrimp farmin g is not available from finance institutions. This drives shrimp farmers to take loans from sh rimp traders, who demand monopoly purchase rights of the shrimp crop in addition to repa yment of the loan a high interest rates. Loans should be made available at normal interest rates by finance instit utions 6. Chain of traders: The system of having several intermediate traders between the shri mp farmer and the processing plant (as well as the fraudulent practice of ‘cooling’ shrimp in cold water to increase their weight) results in deterioration in quality of the shrimp.61 Atte mpts by plants to buy directly from shrimp farmers have not been successful because the tra ders have monopoly rights to purchase the shrimp in exchange for giving loans to the farme rs. 7. Icing shrimp : There is also the problem of preserving shrimp after harvest, as icing of shrimp is not properly done. There is not enough ice available, or in the right locations. 8. Shortage of raw material for processing: Processing plants suffer from a shortage of s upply of raw material, especially high quality raw material which would realize premium prices on export markets 9. Unplanned development: Much of the existing shrimp farming development was un planned. No survey has been conducted to determine the areas suitable for shrimp farming. Farms are set up where soil conditions are unsuitable for bagda (too acis, high pyrits content , high organic matter content). A survey needs to be done and potential shrimp farming are as identified and categorized in terms of their suitability for shrimp farming.
- 9. 10. Regulation of shrimp farming activity: are not regulated. Such criteria as stocking ti me and stocking density are up to the framers There is no control over farming practices, su ch as initial stocking density and use of chemicals. The shrimp farming practices. Conclusion The beneficial influence of mangrove forests is not limited to the immediate geographical area in which they grow. They exert balancing ecological influences that are felt far beyond their immediateboundaries. Although exploitation of mangroves for a long time and large- scale conversion of man-groves to aquaculture and other forms of resources have caused serious consequences, it is not impossible to rehabilitate the resources if proper attentionis paid and effective management programs is for mulated and practiced. A number of reports suggest that the mangrove Sundarbans of Bangladesh has been under a simple, easy-to-implement management regime which was installed more than a hun-dred years ago. The management regime has ensured sustainability and if the management practices are followed properly, this will ensure maintenance of the stands in stable condition for an indefinite period of time.Bangladesh is as rich in terms of its naturalresources as it is poor in terms of its inadequateresource utilization and mobilization of its large human population to productive and development purposes. Therefore, Bangladesh has to give a new look to its natural resources particularly to the coastal resources of how they can be used for sustainable social and economic development of the country.In old days, there was very poor knowledge on mangroves, and the forests were exploited without any scientific background, not considering the future implication of the exploitation. However, in recent days, knowledge of different aspects of themangrove resources has increased greatly and mangrove resource conservation, management anddevelopment have been paid considerable nationaland international attention. It has been fully realized and recognized in recent times that we are dependent to a great extent on the mangrove for- ests and they must be conserved for our owninterests.Destruction of mangrove for coastal farming isnow a global problem that has created considerable debate worldwide and need proper attentionand immediate action. The numbers of shrimp producing and consuming nations are very few.These relatively few countries should provide a clear field of action on specific demands. Thegovernments of these producing and consumingcountries have a fundamental responsibility to enact legislation and enforce regulations to protectcoastal and marine environments from destructiveaquaculture practices. References 1. ADB/UNDP,1995. Developmentperspectivesof the ForestrySectorMasterPlan.Bangladesh. Ministryof Environment andForest.Governmentof the Peoples’Republicof Bangladesh. 2. Balley, C.1988The social consequencesof tropical shrimpmariculture developmentOceanShore Management113144Google Scholar 3. Baran, E., Hambrey, J.1998Mangrove conservationandcoastal managementinSoutheastAsia: whatimpact onfisheryresources?MarinePollutionBulletin37431440Google Scholar 4. Begum,A.,Nazmul S.M., 2002. Social aspectsof Shrimpaquaculture inBangladesh.Report preparedunderthe WorldBank,NACA,WWF andFAO ConsortiumProgramonShrimpFarming and the Environment.WorkinProgressforPublicDiscussion.Publishedbythe Consortium. 5. Blower, J.1985aForest InventoryProject,Bangladesh.Wildlifeconservationinthe Sundarbans. ProjectReport151OverseasDevelopmentAdministration,LandResourcesDevelopment CentreSurbiton,UK39GoogleScholar 6. Blower, J.H. 1985bSundarbans forestinventoryprojectBangladesh.Wildlife Conservationin SundarbansOverseasDevelopmentAdministration(ODA)EnglandGoogle Scholar 7. Chaffey, D.R.,Sandom, J.H. 1985Forest InventoryProject,Bangladesh:aglossaryof vernacular plantnamedand a fieldkeytothe treesOverseasDevelopmentAdministrationEngland23Google Scholar