author(s)
Noor M Salman

abstract
The objective of the present study was to detect histopathological changes in Tilapia fish were obtained from meeting point Tigris River, with the Diyala River in Al-Zaafaraniya area. As well as description clinical signs and behavior of Tilapia fish. The weights ranging from (40-70)gm, mostly females and total length ranging from (15-17)cm. transferred to Ichthyopathology Laboratory of college of Veterinary Medicine in University of Baghdad by cork to conduct the necessary tests in a sterile laboratory conditions. Results of Histopathological changes in gills characterized by Epithelial lifting of secondary lamella, Central Venus Sinus congestion and secondary lamella fusion. Fish behavior was recorded showed abnormalities after exposure to the various degree of contamination such as swimming disorders, the fish tended together at the surface, decrease in respiration rate, fast movement, fish weakness, opened and closed in operculum festally, this study referred to importance of environmental pollution and its direct relationship on fish from its influence histological on gill fish which is considered the most important organ of the fish, it is responsible for the process of breathing and gaseous exchange in the fish.