Growth inhibiting hormone

For the breeding of Resplandor (my HM plakat betta) I have done a lot of reading and I came across a phenomenon called the 'growth inhibiting hormone'. Apparently the largest fry release this hormone in order to slow the growth of the rest and have 'more territory' aka more food for themselves.

Of course in the wild this will definitively keep competition at bay and I can imagine that the slower flowing the water, the more influence this will have over other fry in the neighbourhood.

A betta breeder considers that the fast growth she obtains with her bettas (her bettas start colouring up after 3 weeks instead of the normal 8-10 weeks) is thanks to the good food but not in the least to the daily water changes that she performs to remove or dilute this hormone.

She prefers the daily water changes over separating the larger fry from the smaller ones.

Have other people here noticed this phenomenon? Do fish from high current water bodies release this hormone as well?

I have read about the phenomenon, however I did not test it at all. I don't see the fish in areas with current would have even a remote chance for having this adaption. The amount of water rushing through would dilute the hormone quickly resulting in no effects in competition with a lot of wasted energy put into creating inhibitive hormones. I can see this only being an effective tool when it comes to loving in small ponds, even then just how much can be secreted from a tiny fry at that size?

It actually is a well known issue in fry raising. It doesn't take a lot. Young fish rarely go into the current. You catch them in ponds, puddles and eddies off the main stream - in the calmest and slowest parts of the habitat. Lift up broad leaves or grasses hanging from the bank onto water a few centimeters deep, and that's where the fry are. So the hormones would actually have a lot more effect than we might think.
Fish chemical communication is overlooked in tanks, but the chemicals build up,. Corys are famous for that - not growth hormones but warning compounds.

More reasons for water changes...

Fasinating. I've always done frequent water changes in fry tanks to remove excess hormones but didn't know exactly how they worked.

I am actually seeing a big difference in fry size so now that I have filled up the tank, I will start to do water changes.