I cannot directly answer your question, but I can offer a tip...Match the Hatch.

It is a term I use often. Match the hatch. It basically means matching your bait or lure to what the fish are eating at the time.

If the perch you are talking about are Nile Perch, then they have no single food source. They will eat what ever is there at the time. But, at times one particular food might be in plenty.

Lake Nasser, being a man made lake, might be "stocked". That is fry (baby fish) might be released into the lake to keep numbers up. If that is the case, then the perch would go for small live fish. Or maybe there are seasonal food sources like grasshoppers etc.