Red claw are similar to native American crayfish in their general anatomy, reproduction, and feeding habits. However, there are some important differences. These include:
- larger potential size,
- higher percentage of dress-out (meat),
- multiple annual spawning and higher fecundity (fertility),
- nonburrowing and nonagressive behavior, and
- growth at temperatures ranging from 70 to 90o F.
Red claw can reach a weight of 2 to 4 ounces (50 to 100+ grams) in a seven-month growing season while native crayfish normally grow to about 1 to 1 1 /2 ounces (20 to 35 grams) during a growing season.
Furthermore, about 30 percent of the total body weight of the red claw is edible tail meat compared to 15 to 20 percent for native crayfish.
Both red claw and native crayfish reach sexual maturity at less than one year of age. However, native crayfish are considered seasonal spawners. Day length and temperature changes are necessary to promote fall and spring mating activity.
Red claw are multiple spawners capable of spawning several times (3 to 5 times) each year as long as water temperatures remain above 75o F. Red claw do not excavate deep burrows like native crayfish. Red claw will occasionally dig shallow depressions or short burrows.
When burrowing does occur, it is usually in the deeper portions of the pond and does not damage dams or levees. Another major difference between red claw and native crayfish is the water temperature requirement.
Native crayfish are from a temperate climate and generally tolerate a wide range of temperatures. They are more active and grow during the cooler months and usually spend hot summer months in burrows underground.
Red claw are native to the tropical region of northern Australia. Therefore, red claw grow best in relatively warm water (75 to 85o F) and will not tolerate cold temperatures. Water temperatures below 70o F significantly reduce growth rates.
Water temperatures below 50o F are lethal and will limit red claw production in outdoor ponds to a 5- to 7-month growing season in the Southeast. Much of the hatchery and juvenile production will need to be done indoors during the cooler months.
Red claw and native crayfish are both omnivorous detritivores, meaning that they prefer to eat decaying plant or animal matter.
In their native habitat their diets consist mostly of decaying plant material. Under culture conditions both species have been found to readily accept a wide variety of foods including formulated diets.
Red claw, like native crayfish, seem to tolerate a wide range of water quality conditions including: dissolved oxygen (>1 ppm), hardness and alkalinity (20 to 300 ppm), and pH (6.5 to 9). Adult red claw have been shown to tolerate dissolved oxygen to as low as 1.0 ppm but young are more sensitive to low dissolved oxygen.
Red claw have been known to tolerate unionized ammonia concentrations up to 1.0 ppm and nitrite as high as 0.5 ppm for short periods without noticeable adverse effects.
An important behavioral trait, from a culture standpoint, is that red claw are relatively gregarious and tolerate crowded conditions to an unprecedented degree for a large-clawed crustacean.
Even at densities greater than 50 per square yard, adults show limited cannibalism. This trait may reflect an adaptation to the environmental conditions this species experiences in tropical Australia, where pronounced wet and dry seasons cause them to congregate at relatively high densities in water holes during the dry season.
Under these conditions nonaggressiveness is a critical adaptation to survival and repopulation. Once the rainy season begins they disperse by migrating into newly flooded areas. Juveniles are more aggressive and display a degree of cannibalistic behavior.
Authors:
Michael P. Masser and David B. Rouse
