The only changes I have seen was a tendency for one strain of Peacock Gudgeons to have more black pigmentation in the fins. As most members of this list know females have a black line along the anal fin which is for me the earliest sex differentiation cha
racteristic. This particular strain were getting black in the first and secnd dorsals as well in both males and females. There was no noticeable change in vigour but I have never raised more than 40-50 fry per spawning anyway with this species.
Bruce Hansen ANGFA