When looking at some fish, you can easily spot the physical differences between the two genders. For example, female beta fish have a white spot on their bellies. In the case of catfish, females have smaller heads than the males. With crappies, however, it is more difficult to tell the difference between a male and female. Still, it is not impossible to tell the gender of this extremely popular member of the sunfish family..
Size is not a good indication of sex because male and female crappies are usually the same size.
Look for eggs or newly hatched fish nearby. If the crappie is guarding a nest, this is a male. The females lay the eggs and then quickly leave the area.
Check the color of the belly and fins prior to and during spawning, suggests biologist Mike Colvin during an interview with "Game & Fish" magazine. On a male crappie, these areas will change to a black color. The coloration of the female will not change.
Look for a swollen belly prior to spawning season. Mature females can carry more than 100,000 eggs.