Common Yabby (Cherax Destructor)

Common Yabby, Australian Freshwater Crayfish, Blue Yabby, Murray River Crayfish

Distribution

The blue crab (Yabbi) is a water-land crustacean that naturally inhabits swampy areas, freshwater streams, rivers, lakes, and lagoons. These waters are characterized by a very high degree of oxygen saturation, rich vegetation, muddy bottom. In nature, these crayfish can survive in waters with temperatures ranging from 1°C to 35°C, however, below 15°C they enter a state of partial hibernation (there is a cessation of food intake, inhibited growth of the animal, and a significant slowdown in metabolism).

Appearance

In natural conditions, the color of this crayfish's shell is olive green to brown with blue, yellow, orange or red discolorations (mainly on the legs and from underneath). This color results from a variety of habitats. In aquaristics, specimens available come from selective breeding and are therefore entirely blue. This crayfish is also distinguished by its strong, broad and elongated pincers and smooth shell. Males and females can be distinguished by looking at their bellies. The female has a clearly visible sperm packet located centrally between the 4th and 5th walking legs. Males can be identified by the transformed first two pairs of abdominal limbs, which converge and are parallel directed towards the belly.

Temperament

A fairly aggressive and territorial crayfish (especially if kept alone) - chooses a territory where it builds its nest/burrow. They undermine decorative elements in the aquarium - hence they should be placed stably. They attack ground fish and shrimp, they pinch fish with veil fins. They gnaw at plants, even those that seem unappetizing, e.g dense. They are most active at dusk and before dawn, but this activity can be influenced by regulating the intensity of light and water temperature (bright light and extreme temperatures are not beneficial). During the day, they usually hide and only appear at feeding times. Like most crabs, it is a resilient and durable species. Its lethargic mood and climbing onto decorative elements and constantly being under the surface of the water indicate that there is insufficient dissolved oxygen in the water. It should also be remembered that when introducing new crayfish to established individuals, fights will always occur between them.

Aquarium

The most important criterion for crayfish is the surface area of the tank bottom - the larger the better. The second important thing is to provide them with a sufficient number of hiding places, especially when they will be kept with other animals. They must be prepared so that they are not visible to each other. We use stones, rocks, caves, pvc pipes, wooden (e.g. bamboo), ceramic, coconut shells, roots, and sticks, etc. to build them. Here we need to take into account the size of the animals - so that they do not get stuck. Properly chosen colors of the equipment allow emphasizing and intensifying the coloring of the inhabitants. Thirdly, for these crustaceans, well-oxygenated water is essential for life. Crayfish have gills and do not breathe atmospheric air. They can indeed stay on dry land, but only until their gills are moist. From an aquarium that will lack oxygen, the crayfish will attempt to escape (a tight tank cover is necessary). Crayfish like to stay in murky waters, but that does not mean the water should be dirty. These animals are sensitive to the presence of ammonia and nitrites. Therefore, effective filtration and regular partial water changes are required. The lighting should not be too intense, preferably diffused. When choosing a substrate, use those with delicate, rounded edges. From time to time dry oak, beech or almond leaves, and dried alder cones are laid on the bottom of the tank (necessary ingredients of the crayfish's diet).

Reproduction

Under natural conditions, the reproductive period of these crayfish often begins in the summer, to reach its culmination in late autumn and winter. This species usually reaches sexual maturity at a body length of 6-10 cm. Females typically lay eggs several times during one breeding season, even up to 1000 eggs (when the female is older and experienced, young mothers lay 100-300). Fertilized eggs are olive-colored, oval-shaped, and 2 mm in size. The female carries the eggs for 19-40 days, depending on the water temperature. If the tank is not spacious enough (its bottom) and we have only one female, it is advisable to separate her from the male during the carrying and rearing of the young. Otherwise, she may be tormented to death by the male. Larval metamorphoses occur in the eggs and end with the first molt. Young ones grow quickly and initially molt every few days, later less often. Small crabs eat the same food as large ones.

Food

This species of crayfish is omnivorous, but prefers plant food - especially rotting, decaying plant residues. Their diet must therefore include plant food: dry or fresh green vegetables (peas, lettuce, zucchini, spinach), algae, etc. They also willingly consume frozen and live animal food: shrimp, fish, meat. It is important that their diet is varied (then their hunting instincts are greatly limited), and the food sinks to the bottom. It is also necessary to enrich their diet with alder cones, oak, beech or almond leaves - ingredients contained in these products reduce the risk of ulcers appearing on the shell (so-called rust spot). These products should be brown, dry, and clean, and should be scalded with boiling water before serving. Crayfish also consume their own molt, so we do not remove it. It is a valuable source of calcium carbonate - an essential ingredient for hardening the new shell.