I'm not sure you can vent a JD. You can with rift lake mouthbrooders because the eggs are so large. Once a female has laid eggs its easier to tell. The females will havesex organ is larger than teh anus. The males will be about teh same size.
With JD's you have to wait either until the breeding tube is down. Males are pointed, females are round. Another way to sex the fish is by the coloration on the gill plate.
