Age structure of migrant Kutum (Rutilus frisii kutum kamensky, 1901) into the Tonekabon River
Subject Areas : New Technologies in Aquaculture Development
Keywords: Keywords: Age structure, Tonekabon River, Kutum (Rutilus frisii kutum),
Abstract :
A study was conducted to determine age structure of Kutum Rutilus frisii kutum during its migration to Tonekabon River in spring 2006. A total of 156 specimens were examined. Males and females included 4 age groups, 3+ to 6+ in males and 4+ to 7+ in females. The overall sex ratio was 1:1.33 in favour of males. The age groups of 3+ and 7+ were dominant in male and female respectively. In both sexes, standard deviation of weight was higher than of length. Furthermore, there was a significant increase in standard deviation of weight besides increasing in age. Condition factor was the highest at age 6+ years in male and 7+ in female. Growth model was allometric (positive for females and negative for males) for both sexes. Back-calculation estimated by Fraser-Lee equation showed that for all age groups of both sexes, the back-calculated lengths were less than observed lengths. The parameters L∞, k and t0 of von Bertalanffy growth equations were computed as 130.62cm, 0.06 year-1, -0.21 and 79.87cm, 0.11 year-1, -0.38 for female and male respectively. The results provided basic information on age structure of Kutum in Tunekabon river, in addition, offer evidence that need more in-depth studies of all migratory populations in rivers of south of Caspian Sea.
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