im a keeper of nile perch i have 1 at around the 18"mark sold as lates niloticus and im growing 2 smaller ones that are around 6" that where sold as sp.im wondering what you mean about royal? do you mean the pattern on the body which changes depending on there moods and loose as they grow or are you taking about a differant sub species? i got a few books on nile perch but havnt come across royal unless its a common name for one of the following?
l. angustifrons-lake tanganyika region
l. japonicus-easy to identify japan
l.longispinus- lake rudolf region
l.macrophthalmus lake victoria apparently not a pure niloticus
l.mariae big eye lates
l.microlepis-commn name fork tail
l.stopperii-common name sleek lates
as far as im aware {very limited info on the net and inbooks} theres very little difference in the majority of them except the japonicus other than slight regional variations in juvenille patterns.
