Impact of changes in water quality on the infestation of the common carp Cyprinus carpio with fish lice Argulus foliaceus in aquaculture in Erbil province, Iraq

The present study investigates that seasonal distribution and intensity of infestation of Argulus foliaceus in common carp (Cyprinus carpio) in Taq Taq, Kurdistan Region, Iraq, in relation to ecological factors such as temperature, pH, electrical conductivity (EC), and salinity. A total of 90 fish were taken throughout 2024, and parasitological examinations were conducted to assess infestation rates. The results revealed a clear seasonality, with the highest infestation rates (0.667) in summer and early autumn (June–September) when water temperature rise (8.3–19.2°C) and pH levels were slightly alkaline (pH 8–9). Infestation was lowest in winter (December–February), this was due to the reduced temperatures (3.4–5.3°C), which was not favorable to parasite metabolism and reproduction. Statistical analysis revealed that there was a high correlation (p < 0.01) between intensity of parasite infestation and water temperature. This study indicates the impact of ecology on A. foliaceus distribution and also the potential economic threat it poses to aquaculture. Proper environmental management, regular monitoring, and targeted interventions are essential to mitigate infestations and safeguard fish health in aquaculture settings.