en پژوهشي Orginal research papers <span style="FONT-FAMILY: "Times New Roman","serif" FONT-SIZE: 12pt mso-bidi-language: AR-SA mso-fareast-font-family: 'Times New Roman' mso-ansi-language: EN-US mso-fareast-language: EN-US">A study was conducted to evaluate the correlation between selected physico-chemical parameters of water and their effects on growth of Rainbow trout (<i>Oncorhynchus mykiss</i>) in raceway system in the area of Sarab Gerdu, Iran. The samples were collected from twenty raceways (270- day old fish, surface area 55m² flow rate 150 ls^-1 total production 15 T). Physico-chemical parameters were the fluctuations of total ammonia nitrogen, dissolved oxygen, turbidity, nitrogen (nitrates), phosphorous (phosphates), total dissolved solids, electrical conductivity, fluoride, boron, pH, temperature, total hardness, and alkalinity. Multivariate analyses were conducted employing three categories of parameters including A, B and C. The results of the study showed that temperature and pH<span dir="rtl"></span><span dir="rtl"></span><span dir="rtl"><span dir="rtl"></span><span dir="rtl"></span><font size="3" face="Times New Roman"> </font></span>variations were similar. Dissolved oxygen with negative similarity coefficient, _0.618 was located in the third category while positive coefficient, 0.479 of other parameters except for pH and temperature (second category) and dissolved oxygen (third category) was located in the first one. pH value was not in a standard range due to increase in water temperature. This, in turn had impact on other parameters, such as :::union:::ized ammonia, a toxic chemical, to fish. Our result demonstrated that nitrate concentration is the most significant chemical parameter for fish growth in this area. Similarity, increase in concentration of dissolved oxygen in the water (from 3.30 mgl^-1up to 12 mgl^-1) was necessary to promote productivity.</span> multivariate analyses; raceway system; aquaculture; rainbow trout 245 254 http://jifro.ir/browse.php?a_code=A-10-1-5&slc_lang=en&sid=1 R. Moogouei r_moogoui@iau-tnb.ac.ir 1003194753284600133 1003194753284600133 Yes A.R. Karbassi 1003194753284600134 1003194753284600134 No S.M. Monavari 1003194753284600135 1003194753284600135 No M. Rabani 1003194753284600136 1003194753284600136 No A. Taheri Mirghaed 1003194753284600137 1003194753284600137 No