A yabby, also known as a freshwater crayfish, is a type of crustacean that is found throughout Australia. You can find them in rivers, creeks, lakes and other bodies of fresh water. They spawn in the colder months of December through February, where females carry about 1,000 eggs underneath their tails for three weeks. It is easy to tell the difference between a male and female yabby, especially in breeding season when you can see the eggs under the female yabbies.
Place rubber bands on the yabby's claws to keep it from snapping at you while you pick it up.
Pick up the yabby and look at the area where the walking legs are to see its reproductive organs, called gonopores. The walking legs are the four pairs at the bottom. Males have small bumps that look like pimples near the fifth pair of legs.
Inspect the yabby's third pair of legs if you don't see any bumps on the fifth pair of legs. Females have transparent, oval-shaped openings at the base of the third pair of legs.
Look for eggs on your yabby if you are unsure of the gender. They look like a bunch of grapes clustered near the tail. Females might or might not be carrying eggs. If you have one with eggs, look at her genitals near the second or third walking legs to see what females look like so that you can identify genders in other yabbies.