Bolti fish (Oreochrom niloticus) were caught from two different sources (farm water and river water), whereas Mullet fish (Mugil cephalus) were caught from farm water and marine water. Upon caughting fish, pH value and fish oil stability parameters were determined, then fish were subjected to storage at low temperatures (4^oC, 0^oC and -18^oC) for different periods (24 hours, 40 hours and 3 months, respectively). Changes in pH values and oil stability parameters were recorded during storage periods. The obtained results revealed that: pH values of Bolti fish were 6.82 and 6.93 for farm  and river water respectively, where the values of Mullet fish were 6.14 and 6.73 for farm  and marine water, respectively. Upon subjecting fish to storage at low temperatures, slight and gradual decreases in pH values, were recorded, then the pH values were slightly increased thereafter, specially in case of refrigerating temperature (4^oC). Fish oil oxidation parameters (peroxide value, anisidine value, totox value ,diene and thiobarbituric acid) as well as oil hydrolytic rancidity parameter (free fatty acids) increased with prolonging storage period even at low temperature (4^oC, 0^oC and -18^oC). The lowest changes were recorded in case of storage at (-18^oC), where the highest ones were found at refrigerating temperature (4^oC). It could be concluded that fish must be kept at low temperatures after caughting to increase the shelf life of fish , and reduce the risk of forming the unsafe compounds resulting as a function of fish oil autoxidation .