Effects of Alborz Dam in Babolrood River on some reproductive characteristics of Squalius cephalus

This research has been conducted in the Babolrood River (Mazandaran province) for evaluation effects of Alborz Dam on biological characters of Squalius cephalus for one year. The sampling was done monthly at behind and below the dam and samples were collected by Electroshoker. In total, 251 Squalius cephalus caught. Total length, fork length, standard length, body weight, age, sex, gonad weight, egg diameter and liver weight measured and recorded. In station 1 (behind the dam), average of total length and body weight for males was 120.44±23.36mm and 23.23±1.43g, respectively. Also, for females average of total length and body weight was 148.33±18.73mm and 39.91±1.41g, respectively. In station 2 (below the dam), average of total length and body weight for males was 117.08±18.31mm and 22.15±7.17g, respectively. Also, for females average of total length and body weight was 131.47±19.61mm and 31.90±1.62g, respectively. The age of the samples belonged to seven age groups. Sex ratio of female to male, at behind and below the dam was obtained 1:1 and 1:1.69, respectively. Changes in diameter of the eggs in behind the dam were between 0.41 to 1.36mm (average 0.94±0.29mm) and at below of the dam were 0.15 to 1.12mm (average 0.75±0.15mm). Absolute fecundity at behind the dam was estimated minimum 1308, maximum 14911 and average 6417 and at below the dam was estimated minimum 1277, maximum 12779and average 5111. The fecundity rate between the two stations, no statistically significant difference (P>0.05). The mean percentage of sexual maturity index (GSI) for male and female at behind the dam was 2.52±2.39% and 4.66±3.83%, and this index for male and female at below the dam was 3.7±2.56% and 4.09±2.61%, respectively. Mean liver index (HSI) for male and female at behind the dam was obtained 1.18±0.09% and 1.25±0.07%, and for male and female at below the dam was 0.66±0.30% and 1.03±0.27%, respectively. According to results of this study, fish in upstream and downstream of the Alborz Dam in many of the reproductive characteristics had a similar situation.