Quick Guide To Raising Crayfish
Called crayfish, crawfish and crawdads interchangeably, all terms refer to freshwater crustaceans resembling small lobsters that are rapidly gaining popularity as a food product and an aquaponic system accessory. Probably most known for their propensity for taking over non-native water sources, crayfish are becoming increasingly recognized for their usefulness in aquaponic systems.
Crayfish are kept in aquaponic system to promote cleaner filtration and maintain a smoother system. While crayfish are pretty sturdy critters, you will have to make some adjustments to your aquaponic system before introducing them.
The first adjustment your system will require is the addition of hiding places for the crayfish. When not mating, crayfish are extremely aggressive towards each other and will need hiding areas for escaping from their fellows. Most people use small, cut sections of two inch PVC pipe to house the crayfish. These can be dropped randomly onto the bottom of your tank or glued together in a honeycomb pattern with aquarium silicone.
You may also choose to band the claws of your crayfish shut. This is a good option if you notice that they have been catching your fish and tearing pieces from their fins. You will have to periodically replace the bands, since they may pinch when the crayfish molt, and will have to check them at least once per day. The bands will naturally deteriorate in the water, and one loose crayfish in a tank of banded ones will soon be the only live crayfish.
You may not have the opportunity to choose what type of crayfish you stock your system with, but if you plan on breeding them strive to acquire Australian Blue Claw or Red Claw crayfish. These are by far the most popular crayfish for aquarium raising because they go through fewer life cycles, making them easier and faster to grow to a mature size.
It may also be useful for you to understand how to determine the sex of your crayfish, especially if you plan to breed them. Most species have easily visible indicators; for instance, the female Red Claw will have small, round nodules on the third set of legs. Males have sexual organs on the first set of legs, closest to the tail, and have soft, red spots on their claws.
In general you may be able to determine the sex of your crayfish based on the mature size of the claws and tail. Males tend to have larger claws and a narrower tail, while females have smaller claws and a broader tail for carrying young.
Of course, it is easiest to tell the sex after the female has laid eggs. She will carry a nickel-sized cluster of red eggs on her tail. Once you notice these eggs, you must separate the female from the rest of the population or risk one of the males destroying her clutch. After the eggs hatch, the young will remain with their mother for some time. When you notice that they no longer return to her, you may place her back with the population.
The babies will reach a mature size on about six months, requiring eight to nine months if kept in a smaller tank. A size of approximately seventy grams is considered market size.
Crayfish that fight when you lift them from the tank indicate good water quality, while catatonic or slow-moving crayfish usually aren’t receiving enough dissolved oxygen.
You have several options when feeding your crayfish. Some people prefer to grow the crayfish’s food in the aquaponic system and report good results with wheat grass. You may also purchase sinking pellets from any pet store with an aquarium section. As mentioned before, crayfish can live with your system’s fish but may eat dead or sickly stock.
Except your crayfish to molt. This is the time when they are the most vulnerable as their shells will be very soft and weak. It is also the time when most people decide to test how tasty they are, since they are easier to clean at this stage.
You can acquire your crayfish from a variety of places, but don’t take them from public water sources unless you know from a reputable source that this is legal in your area. You can also find crayfish at some pet stores but will likely pay more for them. You other option is to purchase them live from a supermarket. Supermarkets, even ones that sell only cooked crayfish, will often sell you live ones cheaply by the pound.
Like freshwater prawns (For more information about freshwater prawns, check out our article “Adding freshwater shrimp and prawns to your aquaponic system”), crayfish will require some adjustments to your aquaponic system. But, also like prawns, they will help maintain a cleaner system and can co-inhabit in the same tank as your fish.
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