Determination of Length and Weight Relations in SPF Rainbow trout (0ncorhynchus mykiss) Male and Female Fish of Different Population in order to Choose the Best

This research was done to compare length and weight relations in SPF rainbow trout male and female fish of different population in order to choose the best for cross breeding in Tonekabon cold-water fish research center. Collected pre-mature rainbow trout fish from IVO verified propagation centers of West Azarbayjan, Mazandaran, Kohkiloye and Boyerahmad, provinces, divided to seven treatments each with three replications and cultured in cement raceway pond with 10 kg density per cubic meter after tagging for tracing economic growth qualification and bio- securing. Feeding were done based on 2 to 3 percentages of body weight, three times per day, using Skeretting products of 40 to 45 crude protein percent and water exchanged 4-6 times, daily. Biometric indexes of fishes and physico chemical water parameters were measured during different growth stages. Since male and females placed in the same culture condition, so environmental parameter changes and genetic interactions variances were not influenced. Growth equations survey revealed that the highest b index of male broodstock, 3.15 was found in Maroofi propagation center in West Azarbayjan province which is showed growth isometric, the highest b index of female 3 was in Sarshar center (Mazandaran province). Invariability in fish sizes were caused by reduced heterozygosity which made economical performances by harvesting same weight and length fishes during shortages period. The highest correlation index R2 of male fish 87%, were observed in Maroofi center (West Azarbayjan) followed 0.86, 0.84 and 0.82 in Sharshar (Mazandaran), Ghorbani (West Azarbayjan), Fakhari (Mazandaran) and Yasooj (Kohkiloye and Boyerahmad) centers, respectively. Based on obtained data, the best broodstock of rainbow trout fish were selected and made identification certificate for cross breeding.