The present study aimed to estimate percentage of red and white muscles fibers in two species of bony fishes belong to two different families which represented by Tenualosa ilisha (Hamilton , 1822) that belongs to the family Clupeidae and Cyprinus carpio (Linnaeus , 1758) that belongs to the family Cyprinidae . The samples were collected from local market at holy Karbala province. The results show difference clear in mean values of muscles numbers at different studied length groups, and the percentage of red muscles fibers were less than that of white muscle fibers at different body regions (R1,R2,and R3) among species. The total average of red muscle fibers values ranged between (4.23 - 11.08 %) while the total average of white muscle fibers ranged between (88.30 - 95.33 %) in both fishes species. The results also showed the percentage of red muscle fibers increased toward posterior end of the body (at caudal peduncle) which related with their role movement and swimming of fishes. From the results of the present study, we can conclude that both species under investigation are stayers fish depending on the proportion of red muscle fibers in muscle system in fish body.
