The habitat of crayfish

    Crayfish - invertebrates are valuable, constantly in high demand all over the globe. Unfortunately, the natural population of annual decline, helped by poaching, recurring epizootics and various other reasons.

It is established that the natural stocks of crayfish reach a maximum every 7 years, and then begin to decline to a minimum. In recent years, much attention is paid to crayfish in artificial ponds. Turkey leads here, which at one time were imported crawfish from ponds in Ukraine. The external market, it annually provides up to 7 tons of commodity cancers, and several smaller - Spain (3.5 tons) and China (1 thousand tons). In home gardens and suburban ponds can successfully cultivate fast-growing species of crayfish, as shirokopaly (Astacus astacus) and long-toed (Pontostacus lepto-dactylus). Crayfish can live in any fresh water - rivers, lakes, estuaries, reservoirs, ponds, etc. They love to clean, not contaminated by chemical, household and / or industrial wastes natural reservoirs (not for nothing that they are considered indicators of clean water), whose depth typically 2-5 m, but in some cases can reach up to 8-15 meters ideal environment to habitats of crayfish - the shoreline of the reservoir to the brook, where well-developed aquatic vegetation (elodeya, hara, Ceratophyllum, etc.), covering (but not completely) the bottom of the reservoir. By eating algae in animals accelerates calcium metabolism, and this contributes to hardening of the shell after molting. Crawfish prefer the fairly dense bottom (sand, clay), with the presence of calcareous rocks, stones and water from a normative or high salinity water. Soil bank and bottom of the reservoir should be such that the crayfish was convenient to construct burrows, although they can live and under stones, roots and all pnyami.Chasche crayfish burrows built on steep shady banks, where there is little sun. The usual size of a normal length - 7-36 cm, width - 4-18 cm, Height - 2.16 cm in winter they are at a greater depth and in the summer - at least. Dig their burrows crabs with legs and tail, with the front claws. By the way, the tail they need not only to dig burrows, but also for swimming. Swimming crabs, as you know, backwards, and thus beat the tail on the water. At the bottom they move slowly and often also backwards. It happens that the crabs leave the water from contaminated water, traveling by land. In water with acid reaction they usually do not live. The optimal number of oxygen dissolved in water for Crayfish - 6-7 mg / L, although they may be short-term decline of its level of 2-3 mg / liter. Usually crabs are nocturnal, but if they pochuyut prey, they will strive for it, despite the time of day. Interestingly, and this fact, females are always sitting alone in their burrows, while males during winter is often gather groups and burrow in the mud.

Crayfish - unisexual animals. Males are long-toed cancers, for example, reach sexual maturity at three years of life with a body length of 8 cm, and females - only the fourth year in a body length of 7 cm Usually, crabs males are 2-3 times larger than females. Mating occurs in autumn or (October-November) or in late winter - early spring (February-March) at a temperature of 10 ° C. Duration of pairing - 2-3 weeks, fertilization outside. Males stick their spermatophores on the underside of the cephalothorax of female in a white spot. In the late pairing and low temperatures, fertilization occurs within a few days. Females lay the eggs at night, in silence, for 2-3 hours. Bending the abdomen to the cephalothorax, they form a chamber into which produce a special substance which dissolves sticky there spermatophores with sperm. The eggs, extruded from the oviduct, pass through the seed solution, fertilized and attached to the legs or abdominal armor. Fecundity of females depends on their size, physiological condition, season and other factors. The feet, they may be 110-480 eggs. Due to the movements of walking legs and abdominal eggs constantly washed with fresh water. During the period of gestation female calves are very cautious, hiding in caves and out of them only in search of food. The embryos in the eggs develop within 7-8 weeks. At this time the female took care of caviar, washed with water and clears mucus. Small crabs (larvae) hatch from the eggs usually in late May and early July at a temperature of 21-24 ° C. The first 2-3 days they hang on so-called hyaline filaments, then the thread breaks, and crustaceans with small recurved hooks on the claws are attached to the shell eggs. In this state, they are 5-8 days, eating only at the expense of reserves of yolk, which is located under the dorsal carapace cephalothorax kids. Before the tenth day is the first molt, after which the larvae resemble adults cancers. Their mass is 21-30 mg, body length - 1.1-1.2 cm feed on crustaceans independently, but under adverse conditions, hiding under the belly of the mother. On the thirteenth to the twentieth day is second moult, after which the larvae become completely independent. During molting, crustaceans found in the shelter. During this time they grow up, straighten legs and begin to move the claws, whiskers, eyes. Between the shield and abdomen golovogrudnym a gap, from which protrude crustaceans his soft body. Sometimes the claws and legs torn off, but then they recovered. Most often, time molting occurs in May - August. Molting in crustaceans is many times: in the first year of life - 8 times a second - 4-5 - the third 3-4. The first 1-1.5 months of life for the little crustaceans - a very dangerous period: they are particularly susceptible to disease, they can eat fish, muskrats, waterfowl. Another interesting feature of the lives of cancer. In search of food, they migrate, feeding mostly on invertebrates (worms, mollusks, insects and their larvae, small crustaceans, etc.), as well as calcium-rich aquatic vegetation, small fish. It's very interesting to observe the process of eating crawfish food. If the output is close to the hole, then they carry it in my shelter when away - a cancer eating prey on the spot, hiding in any cover. The optimum ambient temperature for nutrition adult cancers - 17-21 ° C, the larvae - 18-23 ° C. In spite of careful nursing females in their offspring, crayfish can eat each other. This phenomenon is caused by a group way of life of animals, frequent molts, uneven growth. Large individuals consume smaller ones. Crayfish, like all animals are sick. Often they strike and plague rzhavopyatnistaya disease. On the shell of animals can settle various mollusks (especially dreyseny, filamentous algae), but crabs molt their fold. Breeding Crayfish engaged in many countries around the world. In addition to Turkey, Spain and China are Russia, USA, Germany, etc. Each country has developed its own technology of cancers, but the basic requirements are: the presence of water bodies with muddy bottoms and malozailennym water enriched with oxygen to maintain a constant temperature of summer and hydrochemical regime. For breeding crabs, you can use specialized, farmers, and small private and private plots, which contain water. There are two types of farms in crayfish - the pond and the plant. Most cost-effective will be the first since crayfish - the process is fairly labor intensive. Beginners rakovodam advisable to start growing fingerlings, the realization that at constant commodity market can give a significant profit. When breeding crayfish harvesting is essential female living with caviar on pleopods (legs) and their transport to the lobster industry. To grow a ton of crawfish, you need to prepare 500-600 females, they are caught in natural waters. The farm (small ponds, pools or special equipment) carried doinkubatsiyu embryos are on pleopods. It is very important to have a good water exchange and aeration of water. Crayfish need constantly monitor the water quality, control the amount of oxygen dissolved in it (at least 5-7 mg / l) and hydrogen (7-9 mg / l). Water exchange should be about 50 l / min to 1000 square meters. m of water area. It should also carefully examine the natural food resources of the water: algae, zooplankton, worms, "weed" fish, etc. The presence of the natural food supply can reduce the cost of rearing fingerlings and commercial crayfish. Producers of crawfish are placed in ponds (total area - about 0.1 m, depth - 1-1,5 m, planting density - 1-5 pcs. Per 1 square. M). When the water temperature is above 7 ° C crayfish fed fresh or cooked food (meat, abattoir waste, vegetables, shellfish, etc.). Average daily rate shall be 2% of body weight for cancer. Food placed on wooden trays (40x40 cm). In the pond method of breeding crabs - the first stage larvae emerge in May - June. After the second moult juveniles (animals that have not yet reached adult size crayfish) are caught and transplanted into the mother pond, and small crustaceans doraschivayut fingerlings weighing up to 10.7, the doraschivat They can be in the same pond or transplanted to another, in which the conditions meet the requirements of hibernation. Yearlings caught crabs and transplanted into feeding ponds where stocking density is less than the previous lake. In the late second or third year crabs reach marketable weight 40-50 g at 9-10 cm length kept and bred cancers and can be at home (tanks, tubs), but in this case, receive only a small number of larvae (copepods) . A lot of trouble delivering their feeding and preservation. Thus, crayfish grow to marketable weight at home very difficult. In order to obtain 4.3 kg / ha of marketable products cancers, you must have not less than 3.4 ponds, prepared appropriately. Crayfish are known to be in contaminated water do not live, so the meat they have more pure than that of other aquatic animals. And they themselves in the pond act as orderlies, cleaning water of organic debris. In the backyard pond, it is recommended to plant and long-toed shirokopalyh cancers. In shirokopalogo cancer claws broad, smooth shell, the body length of about 15cm. Long-toed cancer has a long and narrow claws and rough shell; body length is 20 cm, weight of the male - more than 300, winter crabs go to the depth and burrow into the mud. Here they are comfortable, and food in short supply. In the winter, as you know, not enough oxygen in the water, some fish suffocate, fall to the bottom and become the prey of crabs, which, even at low temperatures do not stop actively feeding. Catch crabs with special rods, rachevnyami and openwork, starting from mid-summer to late autumn. Good catch is in the dark waters in the evening, in the clear - from dusk till midnight. Best catches are in the dark and warm night in rainy weather. In order to catch crabs is better preserved and not attack each other, they must be fed nettle, alder leaves, potatoes and other vegetation to provide fresh fish is not recommended, as cancers at the same time arrange a scuffle, during which lose their claws and legs, and thus , presentation.