| Abstract: | Soth west coast of india is blessed with a series of wetland systems popularly referred to as backwaters covering a total area of 46128.94 ha. these backwaters are internationallyrenowed for their aesthetic and scientific values including being a repository for several species fish and shell fishes. this is more significant in thatthre wetlands( Vembanad, Sasthamcotta & Ashtamudi) have recently been designated as Ramsar sites og international importance.Thirty major backwaters forming the crux of the coastal wetlands from an abodefor over 200 residentry and migratory fish and shellfish species. the fishing activities in these water bodies provide the livilihoodto about 200,000 fishers and also provide full time employment to over 50,000 fishermen. this paper describes the changes on the environmental and biodiversity status of selected wetlands, during 1994-2005 period. the pH was generally near neutral to alkaline in range. the salinity values indicated mixohaline condition ranging from 5.20-32.38 ppt in the 12 wetlands. the productivity values were generally low in mostof the wetlands during the study, where the gross production varied from 0.22gC/m3/ day in Kadinamkulam to 1.10gC/m3/day in the kayamkulam. the diversity of plankton and benthos was more during the pre monsoon compared to the monsoon and post monsoon periods in most of the wetlands.the diversity of plankton and benthos was more during the premonsoon compared to the monsoon and post monsoon periods in most of the wetlands.the average fish yield per ha.varied from 246kg in valapattanam to 2747kg in azhikode wetland. Retting of coconut husk in most of the wetlands led to acidic pH conditions with anoxia resulting in the production of high amounts of sulphide, coupled with high carbon dioxide values leading to drastic reduction in the incidence and abundance of plankton, benthic fauna and the fishery resources.The major fish species recorded from the investigation were Etroplus argentimaculatus, Mystus sp., tachysurus sp. and Hemiraamphus sp. . The majority of these back waters are highly stressed, especially during the pre monsoon period when the retting activity at its peak. The study has clearly reflected that a more restrained and cautions approach is needed to manage and preserve the unique backwater ecosystems of south west india. |
| URI: | http://hdl.handle.net/purl/1892 |
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| Bijoy S Nandan,.pdf | (916.1Kb) |
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