A field investigation into the effect of sewage effluent and general water quality on selected immunological indicators in carp (Cyprinus carpioL.)

Carp were held in cages at several sites on a river catchment in South East England. Following exposure to river water, various indices of immune function were measured. These includedin vitrolymphocyte proliferation assays, pronephric and splenic somatic indices and serum lysozyme activity. A significant reduction in both the proliferative responses of T and B lymphocytes and in serum lysozyme activity was recorded in groups of exposed carp in comparison with a control (high water quality) site. The observed lysozyme differences were not reflected in total serum protein levels. Glucose assays were performed to assess chronic stress levels in the fish. This established whether immunological differences were a secondary response due to stress or a direct consequence of water quality. Based on data presented here, it is suggested that the water quality in the River Lea exerts a detrimental effect on fish immunity. However, any additional detrimental effect of treated sewage effluent on carp immunity was not apparent.