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Australian Red Claw Crayfish (Cherax quadricarinatus)
The Red Claw crayfish is a new and very promising aquaculture species. The Red Claw is very similar to the native American species, except that it grows to a HUGE size, almost to that of a lobster! This is a species with considerable potential for commercial culture. The features that made it suitable for aquaculture and the aquarium are its ability to withstand low oxygen levels and warm water associated with the tropics.
Australian Red Claw, Cherax quadricarinatus, is a tropical freshwater crayfish native to Australia. They are often called "freshwater lobsters" for their physical resemblance and large size. They are valued as both a food source and an ornamental species. The Red Claw crayfish is the more common species of tabby in Northern Territory, found in most lakes and rivers in North Australia. It thrives in any tropical freshwater environment. In nature, Cherax quadricarinatusare often found under roots or rocks, where they hide from predators and other species members.
Red Claw crayfish is a delicacy, with the texture and flavor of the flesh comparing very favorably with other commonly eaten marine crustaceans. Fresh Red Claw have a smooth and lustrous shell, deep blue to green in color, with males exhibiting a bright red coloring on the margins of their large claws. Cooked, they present as bright red, typical of premium crustaceans. The meat is arguable more healthy than traditional seafood products, as it is low in fat, cholesterol, and salt. It is one of the largest freshwater crayfish in the world. Average market sizes of 50-150 grams (1 pound = 454 grams) are achievable in 6-12 months, although they can reach out to 600 grams each.
Red Claw Coloration
Generally, Australian Red Claw crayfish are blue to a blue/brown/green color. Because of their selective breeding in the hobby, they will not change to their original coloration, except in times of stress or when fed or housed incorrectly. The blue color seems to intensify when the water is clean, and is more green/brown when left in brackish water.
Red Claw Diet
Red Claw crayfish are scavengers. They are a bottom dweller, and will eat anything they come across, as they are opportunistic eaters. They will eat all of the left over food that your fish miss, as well as detritus and other waste off the bottom of your aquarium. Although it will eat dead or dying fish as well, it is normally too slow to catch healthy fish. You want to offer both vegetables and animal proteins. The primary diet should include plant matter, worms, brine shrimp, bloodworms, or insect larvae, and can include vegetable matter waste from aquaponic systems, such as lettuce, shredded carrots, zucchini, etc. Adding a high protein fish or shrimp sinking pellet, flake food, and dried algae is also recommended.
Red Claw Reproduction
The key points to successful maintenance and reproduction of brood stock in indoor holding systems include:
Select healthy mature adults
Maintain warm temperatures (preferably 75 F to 85 F)
Maintain good water quality
Provide proper nutrition
Isolate berried females to hatching tanks
In hatchery, Red Claw can spawn almost continuously throughout the year if conditions are suitable. Red Claw generally reach sexual maturity by the age of 6 to 12 months. Mature males develop a distinctive red or orange patch on the outside margin of the claws. Usually, mature Red Fish without this color claw patch are females. The sexes are best identified, however, by examination of the genital openings on the underside of the cephalothorax, at the base of the walking legs. Females have e a pair of genital pores at the base of the third pair (counting from the head) of walking legs. Males have a pair of small genital papilla (small projections) at the base of the fifth pair of walking legs.
Individual females do not spawn when going through a growth base (i.e. molting). Each female will produce 100 - 1,000 eggs per spawn, depending on their size and general health. The first spawn of young females usually has fewer eggs than later spawns. Newly spawned eggs average 10 eggs per gram of female. About 30 percent of the eggs are lost during incubation, resulting in average of 7 eggs (that hatch) per gram of female. For example, a female weighting 3 ounces (85 grams) will produce about 600 eggs.
Broodstock and Hatchery
Mature broodstock Red Claw crayfish can be kept at a density of 1-2 per square foot of tank bottom. The ration of females to males in each tank should be between 1 to 4 females for each male. Good spawning success has occurred using tanks with water depths of 1-3 feet. Small rectangular tanks of 15 to 20 square feet have been used successfully, as well as large circular tanks of 15 feet in diameter, with 1-3 feet of water. Example: a 20 sq. ft. tank, 2 ft deep, could be stocked with 5-10 males and 15-30 female mature Red Claw. Broodstock tanks should maintain a water temperature between 75 and 85 for optimal reproduction.
Breeding tanks should be checked every one to two weeks for berried females. Once the fertilized eggs are affixed to the female's pleopods, located on the underside of the tail, it is highly recommended that berried females be moved to a separate tank. To prevent egg loss, berried females should be carefully netted, keeping them with their abdomen curled around the eggs during the transfer to hatching tanks. Incubation takes approximately six weeks and the newly hatched juveniles rapidly become independent. The hatching tank will then become the nursery tank for raising the young Red Claw.
"Homes" are essential, as Red Claw have a low level of aggression, but do require housing. PVC pipe sections in multiple sizes, mesh bags, burlap, rocks, or anything that the crayfish can climb through and hid in for shelter will work. Young crayfish will molt many times during their first year, as they grow quickly, while mature Red Claw will molt only once or twice a year. The shed exoskeleton (molted shell) is used as a source of calcium and is typically eaten by its owner or by other crayfish. Red Claw in tanks can handle a temperature range from 60-90 F. Temperatures below 55 and above 95 will result in casualties.
Australian Red Claw as a Pet
Red Claw crayfish are easy and fun to raise in your tropical aquarium as unique pets. The Red Claw is a valued aquarium species, with their exotic coloration. They are less aggressive than most crayfish, and reproduce rapidly and easily. One Red Claw requires a tank that is at least 40 inches long and 20 inches deep.
The ideal tank environment consists of about five inches of aquarium sand or gravel on the bottom, with pipes, tunnels, decorative rocks and caves. you can plant hardy plants in the aquarium, but small weaker plants won't survive. You will want to make sure the aquarium has a filter to keep the aquarium clean, combined with periodic partial water changes. Use test strips to monitor the pH levels, witch should be between 6.5 to 8. When cleaning the tank, test pH before and after changing the water to ensure levels remain within proper range. Use an aquarium heater and thermometer to measure the water temperature and maintain the aquarium between 77 and 90 degrees Fahrenheit. Temperatures below 55 or above 95 will result in causalities. Test the hardness of the water, as well; they need hard water to thrive. You can add limestone to make the water harder, if necessary.
Plenty of cover should be included, as well, with both rocks and plants. After molten, the crayfish is vulnerable to attack and consumption by others. If the exuviae (shed exoskeleton/ molted shell) is removed from the tanks after shedding, the crayfish will likely die, as this shell should be consumed for the vital calcium. If, however, your water has enough calcium, this will not be an issue.
Red Claw crayfish are excellent escape artists. Red Claw are wonderful climbers and will escape from tanks if the water level is near the tank top, if rocks and decor are large enough for them to reach the surface, or, if equipment, such as air line tubing or heater cords extends over the side of the tank. To reduce escapes, equipment should be suspended from overhead so that it does not touch the sides of the tank, and a lid should be kept on the aquarium.