How Often Do Crayfish Molt?

How often do crayfish molt?
Written by Daniel Paul

You move to your crayfish tank and see an exoskeleton lying outside of your fish hideout. You think your crayfish has died, but don’t worry, it is alive but hidden somewhere because it has molted.

What Is Molting?

Molting is a process by which an organism sheds its hard outer skeleton (exoskeleton) to increase e in size. Like all other crustaceans, crayfish have to molt several times in its life. It is an essential process associated with several changes. The growth of these creatures depends on how often they molt.

Why Do Crayfish Molt?

Growth and reproduction are two biological processes that continue in crayfish life until they die. Growth requires periodic and frequent molting. It is necessary for crayfish because it’s hard and an inelastic shell doesn’t allow it to grow. Although the hard shell is responsible for protecting the internal soft organs, it limits the growth as well. The body of the newly-molted crayfish is delicate and flexible, allowing it to grow and expand rapidly.

Crayfish Body Structure

Crayfish have a multi-layered exoskeleton, which is hardened by Calcium salt deposition, except around the joints where it is soft and flexible. There are 20 body segments which are divided into three regions.

  • Hands with the eye and sensory appendages
  • Thorax with maxillipeds and five pairs of legs-like appendages
  • Abdomen with pleopods

All of the functional, jointed appendages are covered by an integument that replaces when molting occurs.

How Often Do Crayfish Molt?

Molting takes place at varying intervals, occurring mostly in Juvenile than in adults. A crayfish molts about 6 to 10 times during the first year of life. This number reduces to 3 to 5 times in its second year. Approximately 11 molts are required by a young crayfish to reach maturity. Crayfish grow around 7.5 centimeters (3 inches) in length.


  1. The crayfish of Tasmania “ASTACOPSIS GOULDI” may reach 40 cm ( 15.7 inches) in length and weight about 3.5 kg (8 pounds)

  2. The “CAMBARELLUS DIMINUTUS” of the United States reaches only about 2.5  cm (1 inch) in length.

  3. White-clawed crayfish can reach lengths of about 120mm, and weights of 70-80g

In culture ponds, frequent molting and rapid growth usually occur during the spring season due to the suitable warm water and sufficient food supply. A rapid increase in temperature above 80F may cause maturity at smaller sizes, especially when there is a shortage of food, and the population is over.

Factors Affecting The Molting Process.

The ponderable thing is that the rate of growth of juvenile profoundly influences by the following environmental factors:

  • Water parameters like suitable temperature (some crayfish are limited to molt in summer).
  • population size
  • Amount and quality of food available
  • Dissolved Oxygen level in the water

Behavior And Characteristics During Molting

Early Signs

  • Decreased appetite and slower activity level
  • Calcium deposition


  • finding a spot to hide
  • move onto its back and begin fanning its pincers
  • molting starts


  • New crayfish is bigger but vulnerable on several fronts
  • a softer shell that is vulnerable to predators
  • needs to eat the old skeleton to replace the Calcium and gain strength.

How Does Molting Occur?

The overall molt cycle includes the process of preparing for, performing, and recovering from shedding. We can divide this process into five stages.

1)   Pre-molt
2)   Late pre-molt
3)   Molting stage
4)   Post-molt
5)   Inter-molt


It lasts a few days in which the carapace thins out. Calcium deposition starts in the gastroliths that are present on the stomach walls. The flesh becomes densely-packed, and a new, soft, and flexible shell forms under the outer one. Just before molting, a crayfish absorbs lots of water, which causes swelling of the new layer of skeleton resulting in pushing out the older one.

Late Pre-Molt

The crayfish stop eating and seek shelter to hide.

Molting Stage

Molting can last from a few minutes to some hours, depending on environmental conditions and the size of the animal. During this process, the crayfish throws itself into a V-shape and lies on its side. Then it starts withdrawing from the old shell. A newly-formed crayfish emerges from the old skeleton through a split present between the cephalothorax and the abdomen.

During the next few hours, the crayfish( now lighter and vibrant in color) will absorb water, swell and grow 15% in size and 40-50% in weight. The new shell has the same features as the old one had.


Over the three to four days following the molt, the newly emerged exoskeleton hardens. The crayfish has to remain in hiding for at least a week or two as it is highly vulnerable to predation. Its naked body is extra delicate, and it needs time to get harden.


In this phase, the crayfish feeds a lot, consumes its own molted shell too that is enriched with Calcium. It accumulates the essential substances required for the next pre-molt. The tissue replaces the water that has gained before molting. In this way, the crayfish fully grows into its shell, and the cycle of molting and growing continues.

Crayfish As Pets

Crayfish can live in freshwater aquariums as pets. They are timid creatures and may often attempt to hide under rocks or leaves. They can molt in the same way that they usually do in ponds and rivers. It is prevalent for crayfish to die in the aquarium when trying to molt. There are many reasons, one of which is a bacterial disease.

Nutrition During The Molting

Crayfish need an adequate and appropriate diet for proper growth.

 For Calcium and protein:

  • Algae wafers, shrimp pellets, kale, cucumber, green beans, etc.
  • Their own molted shell
  • For Iodine
  • Reef Iodine supplement
  • Fish flakes


Crayfish can live in an aquarium as pets. Their growth depends on how often they molt. They show some unusual behaviors during molting like hiding, staying inactive and not feeding. They need more food after molting to grow adequately.