How to Tell a Boy Crayfish

Crayfish are not the easiest animals in the world to sex, as the gender differences are quite subtle. However, if you wish to breed them in a home aquarium or are just curious as to whether you have a male or female, it is possible. Keep a small group rather than a pair if you plan to breed crayfish, because it is easy to make mistakes.

Things You'll Need

  • Transparent plastic box
  • Magnifying glass
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Instructions

    • 1

      Obtain pictures of male and female crayfish of your species. While the difference between the genders is the same for most species, the exact details vary and it is helpful to have illustrations. Such pictures are available on marine biology and aquarium sites. You need pictures that show the undersides of the animals.

    • 2

      Compare the sizes of the crayfish, if you have more than one. Usually the males are bigger, with more developed claws but slimmer abdomens.

    • 3

      Carefully pick up the crayfish and turn it upside down. Alternatively, catch it in a transparent plastic box partially filled with water. This is less stressful for the animal, although you might not be able to see its body as clearly.

    • 4

      Locate the genital openings on the belly of the animal, using a magnifying glass if necessary. These are tiny holes next to each other. On males, these openings are generally between the last pair of legs before the tail. On females, they are between the third pair of legs before the tail. In some crayfish, the males have both male and female openings while the females tend to only have the female openings.