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Advantages of technology on marine life
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Abstract Intensive shrimp farming has developed rapidly in response to dramatic increase in Seafood demand. It has become a thriving business in many developing countries including Thailand. Shrimp farming and aquacultural activities are mostly carried out in mangroves and coastal regions as they provide a nice habitat. But intensive shrimp farming has adverse impact on mangroves and marine environment. An attempt has been made to find the effect of effluent from shrimp ponds on neighboring surface water bodies in terms of suspended solids and organic matter. The residual salts from the dried shrimp ponds are generally thrown on nearby land. This is causing serious salinity of the soil thus making the arable land infertile and turning them into wasteland. As a case study, a coastal province of Thailand has been undertaken. This paper investigates the environmental impact of shrimp farming on landuse pattern, surface water bodies, marine water, mangrove forests and agricultural land using satellite data. |
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Despite the apparent
economic success of intensive shrimp farming, its sustainability has been a major concern
of the industry. The externalities associated with modern production have become
increasingly evident and now confront difficult problems related to effluent discharge
(Landesman 1994). The effluent laden discharge form shrimp pond can be a potential for
nutrient enrichment and eutrophication of natural water bodies and its impact on coastal
environment has caused greater concern (Phillips et. al. 1993). Increasing, eutrophication
in natural water can lead to ecologically undesirable consequences. Shrimp farming, while
generating important benefits has also contributed to degradation of coastal environment
and this threatens sustainability of the production. The risk of failure increases with
greater stocking density, which requires extra intensive management, meaning more food
input, more water exchange. It relates directly to greater amount of waste being produced
in the ponds, which may eventually reach the flash point of pond carrying capacity by
poisoning with excessive waste.
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| Shrimp farming and Aquacultural activities are mostly carried out
in mangroves and coastal regions all over the world. The intensive shrimp farming has
significant impact on mangroves and marine environment as well. It has been realized that
the polluted water discharge from shrimp farms causes deterioration of water quality of
adjacent water bodies like mangroves and coastal zone. Coastal zones are places of ending
changes. Effective inventorying and monitoring of these changes are required for the
understanding and managing these environments (Pundharikanthan, 1997). |
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| There are many conventional methods to find out the
impact of all concentrations on the ecosystem. These conventional methods only give us the
concentration of pollutant at a particular point or so but can not show the dispersion
pattern or extent of pollution at the same time. Much harder to detect is pollution that
has had great length of time to disperse and hence cover large area, or pollution that
does not emanate from a point source (Clark, 1993). Remote sensing provides better tool to serve all these purposes to give synoptic coverage of water bodies. The greatest advantage of remote sensing technology is that it provides augmented view of spatial and temporal variability of water quality and land use status which can not be obtained by any conventional measuring techniques. Several workers have utilized the satellite remote sensing and GIS for detecting and analysing water qualities like ch-a, SSC, Chemical composition etc. (Alfoldi (1982), Lathrop and Lillesand (1991), Clark (1993)). In the present study an attempt is made to determine the environmental changes that has occurred due to shrimp farming in Ranong, Thailand. The interpretation from satellite data has been compared with past records to estimate the changes. The focus in present work being discussed in this paper is effect on water quality and degradation in forest and mangrove area. |
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| Study Area The study area is located at western coast of Thailand. It has extensive mangrove forests and dense tropical vegetation. The vegetation predominantly comprises of evergreen forests, coconut, rubber and palm plantations. The shrimp farms are frequently seen inside the mangroves or adjacent to it. The physical location of the study area can be given as 9o 50¢ 00¢¢ N to 10o 00¢ 00¢¢N and 98o 30¢ 00¢¢ E to 98o 40¢ 00¢¢ E. The study area is shown in figure 1. The study area has high hill ranges that are covered with tropical rain forests. There are numerous streams flowing down these hills carrying silt and organic wastes in the marine regions. Landsat TM digital image in all the bands has been acquired for the study region falling under scene path no. 130 and row no. 053. Topographic map nos. NC 47-6 and NC 47-10 were used for generating the base map and geo-referencing the satellite data. |
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Methodology Landsat TM bands have been analysed for better understanding and interpretability of marine and coastal vegetation cover. It is found that FCC generated with bands 432 has offered a synaptic coverage revealing the landuse categories such as vegetation species, urban dwellings, shrimp farms, river channels, and suspended sediments. In addition it is found that FCC 531 was more useful in extracting information on minor channels and effluents from shrimp farms. The different vegetation species have also become very distinct in this band combination. Using these two products the areas covered by shrimp farms have been delineated and an inventory has been prepared. By traditional surveying this task is very difficult and often not possible. The pollution control authorities have strict instructions to treat the wastewater and then shrimp farmers are allowed to dump in adjoining channels but rarely such treatment is carried out. There is no check in absence of viable monitoring techniques. In FCC 531 it is evident that effluent from shrimp farms is of different quality showing yellowish shade. This waste is generally a amino compound which are fed to shrimps in form of proteins. The effect of this and other waste regularly dumped in streams is toxic and has adverse effect on fishery and other aquatic life. |
Environmental Impact Due to Shrimp Farming From the published records and inventory from satellite data an analysis is shown in Figure 3 on degradation of mangrove areas in the study area. It is evident that there is gradual decline in mangrove areas since 1961 till 1996. The reason of loss in mangrove Area is attributed to rapid growth in shrimp farming in the region. Shrimp farms are generally developed by clearing mangroves and using the easily available seawater for the ponds. The effluent from Shrimp ponds find a way to the adjoining channels and are further transported to the sea.
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