Did someone ask about world record sizes? lol
Like most fishes in captivity, typical and/or average sizes are larger then typical or average size in the wild.
Agreed.
Unfortunately what's typical, is that most hobbyists overfeed their fish, typically with foods that are higher in protein and fat than a wild fish would typically ever see on a daily basis, in the wild. I have bred and raised a LOT of L. caeruleus over the years, both line bred over many generations, as well as F1, offspring from my friends WC group that he collected in Malawi. IMO 5" should not be a typical size, for a male fish that in the wild is typically 3 1/2". But that's just my personal opinion.
I used to tease a local breeder about his labs, they were a beautiful German line bred strain, but overall fairly large, with females in the 5" range. His line to me always was "I Feed to Breed". lol I'll never for get that, but I raised offspring of his as well, and by controlling the diet I kept his labs the same size as the rest of mine over the years. I guess it's a personal thing, no right or wrong way, I'm just not into power feeding.
My friend who spent 6 months working for the late Stuart Grant at Malawi told me that he was shocked at how small the fish in the lake were, until he realized that he was guilty of the same thing with his fish at home, overfeeding nutrient dense food. He said he barely recognized many species due to the size difference.
Kyle is also the only white person that I know of that has collected as many yellow labs in Lion's Cove, or anywhere else on the lake for that matter - collecting over 100 in a single day. If he says that in the wild they average 2 1/2" - 3 1/2" , then I reckon that is the true average size for this species, in the wild.