This study was applied on 140 fishes of two species, T.zillii as member of Cichlaidae and M.seheli as member of Mugilidae collected randomly and seasonally from Lake Temsah to investigate the prevalence of photobacteriosis. Isolates from two fish species were identified by morphological characterization, biochemical tests and API20E as Photobacterium damselae. 15 fish of M.seheli and 22 fish of T. zillii were infected with Ph. damselae subspecies damselae while 6 fish of M.seheli and 9 fish of T. zillii were infected with Ph.damselae subspecies piscicida. Total prevalence of Ph.. damselae subspecies damselae was 26.42% while prevalence of Ph. damselae subspecies piscicida was 10.71%. Prevalence of photobacteriosis was the highest in summer season and the lowest in winter season. Histopathological studies in naturally infected fishes revealed that there was necrosis and degeneration in livers and kidneys with congestion of blood vessels and hyperplasia in melanomacrophage centers in spleen.
