Caudal Fin Development in Double Red Aggies

[tjd]

I have a brood of double red aggies that are over 6 months old and 2.5+" in length. Of the remaining 11 males there are 7 that developed the pronounced spade like shape in the caudal fin 2 to 3 months ago, the remaining have varying degrees of roundness to their fin. All have dorsal fins that reach almost to the back of the caudal fin.

Does anyone know what is the reason for the difference in the caudal fin shape? Genetics, dominance, or something else? The males with the spade like fin tend to be a little more aggressive. The females also attempt to mate with them more so.

Thanks,
Tom

 

[fishgeek]

sounds like it maybe a testosterone thing, just from your description

my aggies in growout never seem to have more than 1 or 2 obvious males , then when i remove theose males new ones seem to appear, perhaps the round tail is part of the sneaker male look

andrew

 

[tjd]

Hey thanks. I have heard of Discus giving off hormones that inhibit the growth of smaller fish.

I'll try separating out some of the males and see what happens. Good to hear that someone else has experienced this as well.

Tom