SBR- Content.pmd - INBO

7 - FisheriesFertiliser run-off into water bodiesoften results in eutrofication as thewater becomes overly nutrient rich.Eutrofication may increase the yieldof certain fish species, but it isgenerally accompanied by a declinein the number of fish species andbiodiversity. The increase in land areaunder agriculture production and theintensification of agriculture has alsoincreased the use of insecticides andpesticides. 123 An analysis of 20 fishsamples of two fish species in theMekong Basin in Thailand in JuneCommercialisation of agriculture increases the use offertiliser and pesticides1988 showed that all samples were contaminated with at least one type of organochlorinepesticide. Dieldrin, DDT and its metabolites were the most encountered organochlorines, eventhough both DDT and Dieldrin are banned from importation into Thailand. 124Recently, the use of pesticides banned in Thailand, Viet Nam and many other countries has beenreported in Cambodia. 125 In 1999, 100 percent of 81 specimens of 27 different fish species (16freshwater and 11 marine) taken from Cambodia were contaminated with organochlorines andpolychlorinated biphenyls. DDT was the predominant pesticide found at levels ranging from 0.5 –25 nano gm per gm of wet fish. DDT levels were higher in freshwater fish than marine, suggestingthat the DDT originated from inland river catchments. 126 DDT is used extensively during the earlyrainy season to control insects, and mosquitoes in particular. 1273. Aquaculture3.1 Importance of aquacultureAquaculture in the region is a diverse activity encompassing production and sale of fry and fingerlingsand the raising of wild or artificially-produced fry and fingerlings in enclosed or semi-enclosedwater bodies for sale and home consumption. In addition to the farming process, the supply ofinputs, and the handling, processing and marketing ofaquaculture products are the basis of rural livelihoods in manyremote parts of the basin. 128Giant fresh water prawnsCapture fisheries and aquaculture are closely interlinked withthe culture of several farmed species being completely orpartially dependant on capture fisheries for seed supply. 129 Wildriver catfish (P. bocourti) seed is stocked in culture cages alongthe Mekong River in Thailand. Wild river catfish seed andgiant freshwater prawn (Macrobrachium rosenbergii) postlarvaeare still the only sources of seed available for culture insome areas of Viet Nam. Small wild fish are also an importantfeed source for intensive cage culture of snakeheads, catfish,sand goby and seabass (Lates calcarifer) in Cambodia andThailand. 130119