Effect of Shahid Rajai dam on population dynamics of the Ponticola cyrius in down stream Tajan River

To study the effect of Shahid Rajai Dam on Population dynamics of P. cyrius in downstream of the dam, during the April 2012 to March 2013, sampling was carried out monthly by electro fishing. A total of 564 specimens from the first station, 219 specimens from the second station and 263 specimens from the third station were examined and the sex ratio of male to female 1:1.42, 1:1.2 and 1:0.91 respectively, that was the first station with 1:1 were significantly different (p<0.05). At first station, both sexes were four groups of 0+ to 3+ years old, while at the other stations, there were three age groups of 0+ to 2+ year old. Pauly growth pattern in all stations and both sexes were calculated positive allometric. The relationship between length and weight showed a high correlation (more than 0.97). Bertalanfy growth equation was calculated for both sexes’ at all three stations. Absolute fecundity at three stations was 570.87, 330 and 303.5 respectively. Mentioned parameters were determined that the significant temperature difference between the stations caused substantial increase in abundance, longevity and fecundity, and provided a favorable habitat for P. cyrius near the dam.