In the text below I shall try to give a short overview of some of the basics when breeding crayfish. Particular species may have other behaviours and demands. It should be said that my main experience as an aquarist is with relation to fish, but I shall try to convey what little knowledge I have.
Sexing crayfish isn't always easy. The genital openings are located in different places on the body depending on whether it's a male or a female. Males have their genital openings behind/under their posterior pair of legs. Females have their genital openings under the third pair of legs counted from the posterior. However, many individuals have a male as well as a female genital opening, making the sexing much more complicated. But these are always either male or female; usually male but you can't be sure.
Mating and egg carrying
In aquariums, spawning is possible any time of year. The male makes a little sperm packet and places it on the female's stomach. The female then spawns her eggs, passing them through the sperm packet so that the eggs get fertilized. It is not uncommon for the female to lose a claw during this process. She then places the eggs under her tail where they will be kept until they are ready to be released. How long this will be depends on the water temperature and the species, but it will be at least 4 weeks. A lot of other factors can also affect the length of the egg carrying period, such as water quality, and food supply and quality. The mother will watch over the young for a short time after birth.
The fry are very small when they are born but are fully developed miniature crayfish. Fry are usually detritus feeders, which means that they will feed on any decomposing plant parts and food leftovers they can find while scouring the bottom. Vegetable food is preferred and they can be fed boiled lettuce leaves that are left to decay in the aquarium. Be aware of the water quality. Fry are often very cannibalistic and a large aquarium is required if you want a higher number of fry to survive. Sorting fry for size may help the survival rate.
Now you know about their breeding behaviour and how to raise the fry, but how can you get them to breed in the first place? Well, first of all you have to give them the right environment and good food to get them in a condition in which they can spawn. Some species also need different triggers to breed. These triggers may be a change in the amount of light and number of light hours, a change in temperature, change of circulation, etc.
Crayfish usually accept most kinds of food, and I would recommend feeding them a diet based on boiled lettuce, sinking pellets, shrimps, and once or week or so, fish meat. This will get them in good condition and help the female survive the spawning period since she usually doesn't eat while she is carrying eggs.
Many crayfish species can be kept in relatively small aquariums, but I recommend using larger aquariums since this lowers the pressure on the females by the males. The aquarium should be decorated so that a lot of hiding places of suitable size are provided. Hiding places can be created using rocks, roots, flowerpots, coconuts, PVC pipes, and so on. It's important that there is at least one, and preferably several hiding places for each crayfish.
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