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During the last two decades 200 millions of kutum fingerlings were released into the Caspian Sea Rivers annually which supported more than 17 thousand tons of catch yield.  Retrieving agents were used by many researchers for homing behavior of fishes. To understand the effects of morpholine on kutum fisheries return rate, this project was conducted from 2004 to 2008 using elastomer tagging method for return rate evaluation. Brooders were selected from Khoshkrud River and breeding were done in Shahid Ansari hatchery, Rasht. Totally 5480 fingerlings (4-5g.) were used for determining the dose effects of morpholine (3 treatments: 5×10^-7, 5×10^-5, 5×10^-2mg/lit) in return rate and homing of fishes. Totally, 505 fish were caught out of which 34 had visible implant elastomer (Abc) tags. Return rate was higher in morpholine treatments (0.32%) compared to controls (0.09%). Results revealed that there were significant differences between kutum return rates exposed with 5×10^-5mg/lit (0.62 %) with other treatments i.e.: 5×10^-7 (0.15%) and 5×10^-2 (0.37%) during the experimental period (P<0.001). There were significant differences in sex ratio [M(1.42): F(1)] in recaptured kutums in Khoshkrud River ( x2=6.4  &alpha= 0.05  df= 1).Recapturing rate was  6.7 % compare to recapture rate during last 5 year (5%) revealed that morpholine can be used for return rate enhancing in kutum fishes.

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