Abstract: About 70 percent of Earth's surface is composed of water, but only 2.5 percent is fresh water. an‎d a small amount of fresh water is available which makes up the aquatic world. Therefore, optimum use of water resources is very important. In this study, the region has been selected target that the land and water in these areas are useless during the rearing rainbow trout. In this study, the rainbow trout (Oncorhynchus mykiss) was investigated because it is one of the most important cultured species in the Iran and world. The place of study located near at Tajan downstream river area. Duration of the rearing lasted 120 days in autumn and winter (October to March). This experiment was performed at two weight treatments (34.91g±0.14SE and 60.09g±0.13SE) and each treatment consisted of three replicates of 200 pieces (16 square meters) with an aeration intensity of rain water changes 0.2L/s for each pool. Fish feeding in the experimental treatments done according to the number and weight of the fish and the water temperature is calculated as the average of three times a day and due to the high turbidity of the water was floating extruded feed. During rearing period, water physic and chemical factors, nutrition and growth rates were determined. The results showed that Tajan downstream river except for the warm months of the year: June, July, August, September and October, is suitable for rearing salmon because of water temperature of below 20 ° C. But during the period of fish rearing only two parameters, turbidity and suspended solid was excessive and because the turbidity due to plankton organisms has been no impact on fish growth. Studies have shown that initial weight introduced, caused between different parameters of growth and nutritional in two treatments including survival rate, condition factor, feed conversion ratio, specific growth rate and protein efficiency ratio by Duncan test at the five percent which there was no significant difference (P<0.5). Percent survival of fish juveniles in treatments 1 and 2 was determined 91.5 and 93.83, respectively. The rate of survival rate indicates adaptability and tolerance of trout fry in the adaptability to the new environment (water downstream Tajan River). Also treatments 1 and 2, respectively, parameters specific growth rate (1.39 and 1.63) and feed conversion ratio (1.37 and 1.66) were appropriate amounts to the standard conditions for rearing trout. Therefore, careful management of talent in this area there is a period of 7 months for rainbow trout. Introducing weights to the lower growth rate of juveniles with respect to the initial price of rainbow farming can be more economical. The use of unusable soil and water resources for agriculture, industry and health with aimed at developing aquaculture as a practical means to produce healthy food and creating employment is considered easy and cost.

قزل آلاي رنگين كمان , پرورش , آب پايين دست رودخانه , رودخانه تجن

تهران ﻣﻮﺳﺴﻪ ﺗﺤﻘﯿﻘﺎت ﻋﻠﻮم ﺷﯿﻼﺗﯽ ﮐﺸﻮر

ﺟﺪاول، ﻣﻨﺤﻨﯽ ﻫﺎ و ﻧﻤﻮدارﻫﺎ

ﺳﺎزﻣﺎن ﺗﺤﻘﯿﻘﺎت، آﻣﻮزش و ﺗﺮوﯾﺞ ﮐﺸﺎورزي - ﻣﻮﺳﺴﻪ ﺗﺤﻘﯿﻘﺎت ﻋﻠﻮم ﺷﯿﻼﺗﯽ ﮐﺸﻮر 51888