International Journal of Biology Reports

fa The effects of drought on reproduction mode of Artemia urmiana عمومى General پژوهشي Research Urmia lake is located at the northwest of Iran with 5 m average depth .Variations of water discharge and evaporation causes the lake itself to rise and fall, fluctuating by 0.6 to 0.9m. In addition to seasonal variations, there are also longer periods of fluctuations, lasting from 2 to 100 years, with water level fluctuations of 1.8 to 4.0 m. Drought year began from 1999 because of low precipitation and preventing of freshwater input to lake Urmia with Dyke and Dam constructed on rivers. Therefore the average depth was decreased and the salinity was increased from 140 g/l in 1993 to 310 g/L in 2002. A comprehensive monitoring and analytical program began in 1993, employs frequent surveys of Artemia populations, measurment of environmental data, and mathematical modeling to understand the dynamics of the Artemia population in Urmia lake. This information is then used to establish the timing and harvest limits for the commercial fishery in the lake. Since 1993, there  have been six years with large populations of Artemia and record cyst harvests, and three years with relatively poor cyst harvests. In this study, watery years (1993- 1998) and drought years (1999-2003) were compared and following conclusions were obtained: Artemia is stressed by high salinity but even in high salinity more than 300 ppt, active Artemia were observed in Urmia lake. The tendency of A.urmiana  is towards to oviparous. According to analysis variance (one way) data concluded of sampling Artemia and water salinity of urmia lake during 1993-2000 , there are significant differences <95%  ( p<0.05) between salinities group (less than 172 ppt and more than 172 ppt ) and changes reproduction mode from  ovoviviparous to oviparous were obtained. In salinities <172 ppt some populations of Artemia  produced nauplii but   in   salinities >172 ppt only cysts production were observed.   Artemia urmiana, dryness, reproduction model 37 46 http://injbir.com/browse.php?a_code=A-10-1-8&slc_lang=fa&sid=1 M. Hafezieh Yes Iranian Fisheries Science Research Institute (IFSRI), Agricultural Research Education and Extension Organization (AREEO), P.O. Box: 15745/133. Tehran, Iran Sh. Masaeli No Iranian Fisheries Science Research Institute (IFSRI), Agricultural Research Education and Extension Organization (AREEO), P.O. Box: 15745/133. Tehran, Iran