Effect of urban wastewater on age and growth of Chub Squalius cephalus (Linnaeus, 1758) in the Gheshlagh River, Sanandaj

In order to determine the age and growth of Chub in the Gheshlagh River of Sanandaj, two areas were selected; one in upstream of the river (Naysar; high water quality) and the other in downstream (Soaryan; impaired water quality). A total of 280 fish specimen were caught during four seasons. The overall male to female ratio was 1:1.86 in Naysar and 1:0.61 in Soaryan. Both ratios were significantly different from the expected 1:1 ratio (P<0.01). The age of individuals was from 0+ to 5+ in both areas. The overall length-weight relationships were calculated as negative allometric in Naysar and isometric in Soaryan. The fork length and body weight of fish samples in Soaryan were significantly larger and heavier than those in Naysar in most of age classes and in both sexes. The average asymptotic length was calculated as 28.2 cm for male and 35.5 cm for female based on von Bertalanffy growth equation for all fish samples in Gheshlagh river system. The overall condition factor was estimated as 1.53 and 1.5 for male and female, respectively. In most of age classes, the condition factor was significantly larger in Soaryan fish samples in comparison to Naysar samples. Results showed that some Chub biological parameters were different between two study areas. These differences could be due to the entrance of Sanandaj wastewater into Gheshlagh River in Soaryan area.