The lower Mekong River supports one of the world's largest inland fisheries. The total fishery of the Mekong inundation zone from Kratie to the Vietnamese border (but excluding the Great Lake-Tonle Sap inundation zone) was estimated to be about 75,000-80,000 metric tonnes in the l970s (Mekong Committee, 1976a). The annual flooding is of vital importance in maintaining this fishery for several reasons. The inundation zone provides the spawning and nursery grounds which supply the bulk of the young fish to repopulate most water bodies in the basin, including the main river and its tributaries, the many swamps and oxbows, and the paddy fields. The floods transfer millions of tons of suspended and dissolved solids into the water from highlands to lowlands and from the surface of land which has been lying fallow for several months. The flooding also releases nutrients from the soil, vegetation and inundated organic debris. Water enriched in this manner annually supports an explosive expansion of the riverine fish populations.
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