Effect of Water Quality Parameters on Isopod Parasite Alitropus typus (Aegidae) of Ectotherms in Chashma Lake, Pakistan

Freshwater lakes are sensitive ecosystem and respond to the episodic changes from its surrounding environment. The physico-chemical factors of water and biological processes determine the quality of water which in turn indicates the diversity of fauna and flora that the water would support. However, the ecological factors of lake correlating with parasitic isopods under natural conditions are poorly understood. The aim of this study were: i) assessment of monthly variations in water quality parameters of lake, ii) identification and determination of parasitic Isopod burden (Aegidae: Alitropus typhus) on freshwater fishes, iii) impact of water quality parameters in relation to parasitic isopod infestation in freshwater fishes of Chashma Lake, northwest of Pakistan. The results indicated identification of Alitropus typus, which was observed on majority of fresh water fishes namely: Labeo calbasu, Labeo rohita, Cyprinus carpio, Labeo gonius, Crossocheilus lalius, Cirrhinus mrigala, Notopterus notopterus, Wallago attu, Ompok pabda, Sperata sarwari, Chana marulius, Chanda baculis, Xenentodon cancilla, Gudusia chapra and Puntius sophore. The correlation matrix showed perfect significant (p<0.05) association between water temperature, hardness, free CO2 and conductivity. The linear regression model was applied between water quality parameters and isopod infestation, negative trend was observed for turbidity, DO, free CO2, alkalinity and hardness, while positive trend for water temperature, pH, water clarity and ammonia. On the basis of biological productivity, the lake has been categorized as mesotrophic to hypereutrophic in different seasons. The findings suggested that deterioration of water quality with changing seasons resulted to high stress response in fishes making them vulnerable to parasitic infections. Due to the presence of Alitropus typus on majority of freshwater fishes, we are also able to make the judgment that these Isopods have less host specificity. However, further s tu die s o n fish parasitological research, disease control and maintenance of health relationship between fishes and water quality parameters should be needed to implement in tropical lakes.