Artemia population changes on Orumieh Lake

Estimation of Artemia resources on Uromieh Lake during (years2002-2003) showed huge reduction of Artemia cysts and biomass stocks than the previous years. Reduction of average annual precipitation in west Azerbaijan province during last 6 years than previous years from 32centimeter to 21centimeter has reduced the annual entered waters from the lakes basin rivers into the lake from(3.5-4.0)billion cubic meters to(1.8)billion cubic meters. During this period the entered fresh water in to the lake has been reduced, however the evaporation rate from 5750 square kilometer of Lake Surface has been continued at 3to4billion cubic meters per year. In spite of the fact that there are more than 5 billion tons salts on Uromieh Lake and that about 2 billion cubic meters of lake water is decreased annually due to negative balance between entered water and evaporation rate from Lake Surface, the water salinity on the lake has increased From 220 g/l in 1999 up to high saturated level atthe present. Increasing salinity on lake water up to high saturated level has caused to salt precipitate on lakes bottom and the Ionic exchange between lake water and beds natural precipitates that necessary to provide needed ions to photosynthesis was interrupted, so that the quality and quantity of primary productions on the lake has decreased and the lake has change to oligotrophic condition and in some seasons the turbidity of the lake has increased up to 5 meters. Above mentioned integrated factors have reduced Artemia stocks on lake during a few last years and this has resulted in stopping the cysts and biomass harvesting.

Iranian Fisheries Science Research Institute

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