Sexing A. nijsseni fry

[Nain]

My A. nijsseni spawned in mid-February and I now have 18 fry that are growing out. They are all between 3/8 to 1/2 inch in total length. I cannot with certainty tell the sex differences yet. All of the fry have a black blotch on the body starting from the base of the ventral fin that proceeds upward, this blotch being typical of an adult female. However, I do notice that 4 of the fry have no discernable caudal spot. These 4 fry seem to have less black on the ventral fins. Are these males?

 

[Neil]

Nain,
That is entirely likely, but not a sure thing. The black-mark patterning on nijsenni is a little tough with Juvs. Usually you have to wait for the fin development and the cheek spot to give you a better idea of sexing. Sometimes you can put them in a fish bag and shake them up a little. Female will get that lateral spot and cheek mark under the stress. But I would say it is best to just wait a little while longer.
Neil