Cover Image
close this bookShort-term training programme on GIS (Geographic Information System) for fisheries (1993)
View the document(introduction...)
View the documentObjective of the training programme
View the documentProgramme and Resource Persons
View the documentName of the Participants and their Organizations
View the documentInaugural Programme and Addresses
View the documentGIS for Fisheries - An introduction
View the documentFisheries Development Plan of Bangladesh
View the documentData Requirement for Inland Fisheries Planning and Development
View the documentPrinciples of Remote Sensing - Airborne and Satellite Remote Sensing
View the documentSatellite Data Processing and Image Analysis
View the documentFundamentals of GIS
View the documentApplication of Remote Sensing to Environment with Special Reference to Inland Fisheries and Aquaculture
View the documentApplication of Remote Sensing and GIS in Shrimp Farming Areas of Bangladesh
View the documentRemote Sensing Applications for Marine Fisheries Resources in Bangladesh
View the documentPond Concentration Studies in Bangladesh
View the documentInventory of Inland Waters (Based on Study of SPARRSO, 1984)
View the documentFormulation of Periodic Atlas of Structured Information of Fisheries Resources

Application of Remote Sensing and GIS in Shrimp Farming Areas of Bangladesh

Dr. M.A. Shahid
Bangladesh Space Research and Remote Sensing Organization (SPARRSO) Agargaon, Sher-E-Bangla Nagar, Dhaka-1207

1. Introduction

Bangladesh has a long coast and large areas of rich tidal lands. This coastal area offers an ideal place for aquacultural development, specially for shrimp farming due to its high productivity and availability of large number of culturable species of shrimp and fish. Presence of natural mangrove forests in Satkhira-Khulna-Bagerhat and Cox’s Bazar areas provides a unique ecosystem in this coastal region. This ecosystem supports a characteristic groups of shrimps, fish, edible crabs and also carries food for fisheries upon which many coastal communities depend.

Shrimps and fish are being traditionally cultured along the coast for a long time. But now-a-days, shrimp farming areas are rapidly increasing horizontally due to steadily rising price of shrimp in the international markets. In most of the places, these expansions of shrimp farming areas have resulted in low production causing ecological and environmental problems.

The main problem for proper planning and sustainable development of coastal fisheries in Bangladesh is a crucial lack of baseline information about the physiographic environment which make it difficult to assess resources and start efficient development. The conventional methods to collect these information are time consuming and expensive and need a lot of manpower. It is very difficult to visit the coastal areas and error may crop up due to variation of different field survey teams. Alternatively, improvement of remote sensing techniques has provided an effective means to overcome most of the problems.

Remote sensing data offer some unique advantages. These are:

* good coverage of a larger area at a time,
* synoptic view of a given area,
* repetitive coverage of the same area at regular intervals
* provision of high scale data,
* high flexibility for surveying an area at a precise time and at a designated scale.

2. Objectives

The objectives of this lecture are to present the applicability of remote sensing in the assessment and monitoring of coastal shrimp farming areas of Bangladesh. This will focus on the following points:

* Overview of whole coastal zone to find out the areas with maximum shrimp farms along the Bangladesh coast,

* Increasing trend of shrimp farming in agricultural and mangrove forest areas,

* Impact of spatial changes of shrimp farming and mangrove forest areas on coastal environment,

* Geographical Information System (GIS) for planning, development and management of coastal shrimp farming at sustainable levels.

3. Overview of the Whole Coastal Area

An overview of whole coastal area was made to find out the areas with maximum shrimp farms. Landsat (MSS) data of January-February 1977 and February-March 1984 were used for this study. As band 7 of Landsat MSS is water absorption band and band 5 is vegetation absorption band, therefore, imagery of these two bands were blownup to 1:1,000,000 scale for visual interpretation of shrimp farming and mangrove forest areas. Colour composites of Landsat (MSS) bands 4, 5 and 7 were also used for visual interpretation of these features. Results obtained from the study were also compared with the shrimp farming areas estimated through conventional method. These data indicated that shrimp farming areas are rapidly increasing in south-western region (Satkhira-Khulna-Bagerhat) near the Sundarbans mangrove forest and south-eastern region (Chittagong-Cox’s Bazar) near the Chokoria Sundarban mangrove forest.

3.1 Increasing Trend of Shrimp Farming in Agricultural and Mangrove Forest Areas

The overview study on the whole coastal area using Landsat multispectral imagery and false colour composites showed that shrimp farming areas are increasing in Satkhira-Khulna-Bagerhat and Chittagong-Cox’s Bazar regions. Some specific sites were selected from these areas for detailed study and to find out the increasing trend of shrimp farming areas over time and place. These selected areas were Paikgacha and Rampal thanas of Khulna and Chokoria and Maiskhali thanas of Cox’s Bazar districts.

3.1.1 Paikgacha and Rampal Area

These two areas are located in the deltaic part of southwestern Bangladesh. Most of these areas are traversed by-innumerable rivers and were once part of the Sundarbans and are covered by dense mangrove forests. These two areas were selected to locate and measure the increase of shrimp farming area in agricultural lands. Methodology of the study included visual interpretation of Landsat MSS and TM and SPOT imagery, followed by stereoscopic interpretation of aerial photographs, computer analysis of Landsat TM CCTs and incorporation of groundtruth information. The data used in the study included black and white aerial photographs taken during February 1975; colour infrared aerial photographs taken during February 1983; Landsat data (FCC of MSS bands 4, 5 & 7) of February-March 1984; Landsat TM imagery and CCTs of October 1988, and SPOT imagery (FCC) of February 1989.

The results obtained from the black and white aerial photographs taken during February 1975 showed that there was only 1,860 ha of shrimp farming area and that all of these shrimp farms were established outside the coastal embankments by simple dyking along the riverbank. The results obtained from colour infra-red aerial photographs of February 1983 and a Landsat colour composite of March 1984, however, after comparing with ground truth data showed that the shrimp farming area had been increasing extensively inside the coastal embankment in Paikgacha and Rampal areas. A SPOT false colour composite of multisectral bands showed this expansion very clearly.

For further detailed study, three specific sites were selected. Maps were prepared showing the shrimp farming, agricultural lands settlements and water areas at 1:10,000 scale. These maps showed the situation as of February 1975, February 1983 and February 1990, as well as the increasing trend of shrimp farming areas inside the coastal embankment from 1975 to 1990, which were predominantly paddy growing land. The average rates of increase of all sites are shown in Table 1. The settlement and water areas remained almost same. Thus, it was found that the rate of increase of shrimp farming areas was high during the period from 1983 to 1990 and very low during the period from 1975 to 1983.

Table 1. Average Annual - Rate of Increase/Decrease of Shrimp/Agriculture Area for all sites

1975 to 1983

1983 to 1990

1975 to 1990

AARI (%)

AARD (%)

AARI (%)

AARD (%)

AARI (%)

AARD (%)

5.6

1.1

22.6

12.9

13.6

6.6

(Source: Shahid et al. 1990 and 1991)
AARI = Annual Average Rate of Increase (Shrimp Farm Area)
AARD = Annual Average Rate of Decrease (Agricultural Area)

3.1.2 Chokoria and Maiskhali

The Chokoria and Maiskhali thanas are located in the district of Cox’s Bazar in the south-eastern part of the country. The Chokoria thana is mostly coastal plain of Matamuhuri river. A small mangrove forest is located in this thana and is popularly known as Chokoria Sundarban due to similarity of their species composition with the Sundarban mangrove forest. Maximum area of the Maiskhali thana is covered by hills and the remaining part is the coastal plain.

These two areas were selected to locate and measure the increase of shrimp farming area through denudation of mangrove forest. Methodology and data used for these areas were same as previous one.

The shrimp farm and mangrove forest areas obtained from colour infrared aerial photographs of 1983 showed that there were 3380 ha of shrimp farm and 4359 ha of mangrove forest in Chokoria thana. Among the shrimp farming areas, 2555 ha were identified in the mangrove forest of Chokoria Sundarban that were created by removal of mangrove forest. But in the Maiskhali thana only 533 ha of shrimp farming and 2586 ha of mangrove forest area were identified. Most of these forests were planted by Forest Department. On the other hand, 5612 ha and 6613 ha of salt belts were also identified in Chokoria and Maiskhali thanas respectively.

The results of further study on the Chokoria Sundarban area showed that during 1975, the whole of the area was covered by mangrove forest. But result obtained from Landsat TM data of December 1987 showed that almost all mangrove forest were denuded for shrimp farming.

4. Impact of Shrimp Farming on Coastal Environment

The results of these studies clearly indicate that the shrimp farming areas are encroaching agricultural lands of south-western region and these areas are expanding through denudabing the valuable mangrove forests in the south-eastern region.

The shrimp farming may be profitable from the economic points of view. This economic attractiveness of shrimp cultivation caused a rapid increase in areas under shrimp farming in the saline and semisaline tidal rivers of Satkhira, Khulna and Bagerhat. An uncontrolled increase of area under shrimp culture, however, does not seem to be justified. The long term effect of soil salinity should be taken into consideration.

The effect of salinity increase in south-western region has been observed in perennial trees and bushes. Trees like coconut, mango, date and palm respond immediately to higher salinity levels in the soil. Yield reductions are impressive; and it has been observed during groundtruthing that new plantations have been; failing completely. On the other hand, in areas with continued shrimp cultivation, a typical household with a kitchen garden, a pond with fresh water or a reliable tubewell, cattles, ducks and chickens become rare. The cows are reducing in number for lack of food and the remainder are shipped to polders that do not have much shrimp cultivation.

The international markets for shrimp is not a stable one as was noted in 1990. Price fluctuations render the prospects for earning foreign exchange uncertain. Nevertheless, the area under shrimp farming is increasing year after year. The present type of extensive shrimp cultivation, however, may not prove to be very beneficial to Bangladesh. Therefore, we need sustainable and scientific development of a type of shrimp cultivation that earns more and more foreign currency but with less cost to society. Shrimp cultivation could be intensified in smaller areas with a protective salinity buffer and combined with paddy cultivation.

It is now well-known that mangrove forests and their ecosystem play an important role for coastal as well as offshore fisheries and there is a direct relationship between them. The mangrove plays an apparently important role in supplying the nutrients to the fisheries of shrimp farms in the mangrove areas should be done in such a way that neither the mangrove ecosystem nor the fisheries they support are affected. Compared with other development uses, however, aquaculture appears to be the type of utilization that best preserves the ecological condition of mangrove as a biologically balanced environment.

There is possively an optimum ratio of shrimp farm area to mangrove forest area. So the farm should be constructed in such a way that sufficient mangrove litterfall is provided to sustain the biological link essential to maintain the adjacent fisheries.

International Union for Conservation of Nature and Natural Resources (IUCN) 1983, suggested that shrimp farms should not exceed one ha of pond for four ha of natural mangrove forests. But it is not constant for all the countries. Rabanal (1977) stated that in developing shrimp farm, a buffer area of at least 400 metres should be allowed between open water (sea or river) and construction of shrimp farm.

5. Geographical Information System (GIS)

GIS is an information system that is designed to work with data referenced by spatial or geographic coordinates. This technique can be used for development and management of coastal shrimp farming area in Bangladesh. The most important use of GIS is to locate suitable sites for shrimp farming and culture of fish in cage. But before operating GIS, it is better to establish location criteria relative to the known demands of the industry. The data for location criteria can be obtained from a variety of sources. Remote sensing can provide an important source of information to assess site suitability, land cover and land uses. Land uses adjacent to the site will indicate the sources of pollution and other possible water quality problems.

Because the use of mangroves and other wetlands for aquaculture is a sensitive issue, mangrove areas need to be carefully defined in the GIS data base. Remote sensing offers an exceptional opportunity to complete and update its existing mapped areas.

6. Conclusion

These studies demonstrate that shrimp farming and mangrove forest areas can conclusively be identified and located by remote sensing techniques. The Landsat (MSS) data can effectively be used to overview the surface features of the coastal area. The colour infrared (IRC) aerial photographs have provided most revealing information to delineate the shrimp farming, mangrove forest and agricultural areas. The results of these studies have provided information for changes in time frame and these have been found to be very useful in analysing spatial changes for better planning and sustainable development.

7. References

IUCN, 1983. Global Status of Mangrove Ecosystem. Commission on Ecology Paper No. 3, (Eds. Saenger, p., E.J. Hegerd, and J.D.S. Davis), International Union for Commission of Nature and Natural Resources (IUCN), 88p.

Rabanal, H.R., 1977. Forest Conservation and Aquaculture Development in Mangrove Areas. In: Proc. International Workshop on Mangrove and Estuarine Areas Development for the Indo-Pacific Region, Manila, The Philippines., p 145-152.

Shahid M.A., M.A.H. Pramanik and Shahadat Ali, 1990. Remote sensing Applications in Coastal Shrimp Farming Areas, Asian Pacific Remote Sensing Journal, Vol. 4, No. 2, p 3-18.

Shahid M.A., M.A.H. Pramanik, M.A. Jabbar and Shahadat Ali, 1992. Remote Sensing Application to Study Coastal Shrimp Farming Area in Bangladesh, Goecarto-International A multi-disciplinary Journal of Remote Sensing, Vol. 7, No. 2, p 5-13.