The cover is hard, chitinous, serves as an external skeleton. Breathing crayfish with gills. The body consists of the cephalothorax and flat jointed abdomen. The cephalothorax consists of two parts: the anterior (head) and the posterior (thoracic), which are fused together. There is a sharp spike in front of the head. In the recesses on the sides of the spike, convex eyes sit on movable stems, and two pairs of thin antennae extend in front: one short, the other long. These are the organs of touch and smell. The structure of the eyes is complex, mosaic (consist of individual eyes joined together). Altered limbs are located on the sides of the mouth: the front pair is called the upper jaws, the second and third - the lower. The next five pairs of thoracic single-branched limbs, of which the first pair are claws, the remaining four pairs are walking legs. The crayfish uses claws to protect and attack. The abdomen of cancer consists of seven segments, has five pairs of bifurcated limbs, which are used for swimming. The sixth pair of abdominal legs together with the seventh abdominal segment forms the caudal fin. Males are larger than females, have more powerful claws, and in females the segments of the abdomen are noticeably wider than the cephalothorax. With loss of limb, a new one grows after molting. The stomach consists of two sections: in the first, the food is rubbed with chitinous teeth, and in the second, the crushed food is filtered. Further, the food enters the intestines, and then into the digestive gland, where it is digested and absorbed by nutrients. Undigested residues are brought out through the anus located on the middle lobe of the caudal fin. The circulatory system in river cancer is open. Oxygen dissolved in water penetrates through the gills into the blood, and carbon dioxide accumulated in the blood is discharged through the gills to the outside. The nervous system consists of a peri-pharyngeal nerve ring and an abdominal nerve chain.
Color: varies, depending on the properties of water and habitat. Most often, the color is greenish-brown, brownish-greenish or bluish-brown.
Size: males - up to 20 cm, females - slightly smaller.
Life expectancy: 8-10 years.
Food / food
Vegetable (up to 90%) and meat (shellfish, worms, insects and their larvae, tadpoles) food. In summer, crayfish feeds on algae and fresh aquatic plants (pond, elodea, nettle, water lily, horsetail), and in winter, fallen leaves. At one meal, the female eats more than the male, but she eats less often. Crayfish is looking for food without moving far from the hole, but if the food is not enough, it can migrate for 100-250 m. It feeds on plant foods, as well as dead and living animals. It is active at dusk and at night (during the day, crayfish hide under stones or in burrows dug at the bottom or off the coast under the roots of trees). Crayfish feel the smell of food at a great distance, especially if the corpses of frogs, fish and other animals began to decompose.
Hunts for crayfish at night. During the day, hides in shelters (under stones, tree roots, in holes or any objects lying on the bottom), which protects from other cancers. Digs holes, the length of which can reach 35 cm. In summer it lives in shallow water, in winter it moves to a depth where the soil is strong, clay or sand. There are cases of cannibalism. Crawfish crawling backward. In case of danger, with the help of the tail fin, winds up the sludge and swims away with a sharp movement. In conflict situations between male and female, male always dominates. If two males meet, the larger one usually wins.
In early autumn, the male becomes more aggressive and mobile, attacks the approaching individual even from a hole. Seeing the female, he begins the pursuit, and if he catches up, then grabs her claws and turns it over. The male must be larger than the female, otherwise she may break out. The male transfers spermatophores to the abdomen of the female and leaves her. In one season, he can fertilize up to three females. After about two weeks, the female lays 20-200 eggs, which she carries on her abdomen.
Season / breeding season: October.
Puberty: males - 3 years, females - 4.
Pregnancy / incubation: dependent on water temperature.
Offspring: newborn crustaceans reach a length of up to 2 mm. The first 10-12 days they remain under the abdomen of the female, and then go on to independent existence. At this age, their length is about 10 mm, weight 20-25 mg. In the first summer, crustaceans molt five times, their length is doubled, and the mass is six times. Next year they will grow to 3.5 cm, and will weigh about 1.7 g, shedding six times during this time. The growth of young crayfish occurs unevenly. In the fourth year of life, crayfish grow to about 9 cm, from that moment they molt twice a year. The number and timing of links strongly depends on temperature and nutrition.
Rod Cancers European
The genus Crayfish European river - Astacus - includes a number of species that inhabit fresh water in various places of the globe. In the northern hemisphere, Huxley distinguishes several regions with characteristic species for each: Euro-Asian, Amur, Japanese, California, and eastern North. America.
The Euro-Asian region embraces all of Europe and part of Asia, namely the Aral-Caspian basin. Crayfish in this area, mainly Russian crayfish, have been studied by Kessler. In Western Europe, where cancers quickly die out due to river pollution and parasitic diseases, they belong to the species Astacus torrentium, which is divided by several into several subspecies.
Crayfish in Eastern Europe belong to the species Astacus nobilis, divided into several subspecies (according to Kessler and others - species).
The basins of the Baltic and White Seas are populated by broad-legged cancer (Astacus fluviatilis), while the Ponto-Caspian basin is inhabited by long-legged cancer (Astacus leptodactylus) and partly thick-legged (Astacus pachypus).
In addition to these fairly widespread species, in Russia there are species with a narrower range of distribution: in the Caucasus - Astacus colchicus, in Turkestan - Astacus kessleri.
The Amur Region is inhabited by two small species - Astacus dauricus and Astacus schrenkii, approaching Japanese species.
According to the Huxley-Kessler hypothesis, the spread of crayfish in the Euro-Asian region came from the Ponto-Caspian Sea, which existed in the Tertiary era. The first natives were subspecies of Astacus torrentium, but they were followed by AAstacus fluviatilis, which drove its predecessors to Western Europe, but was also driven out by new natives, namely Astacus leptodactylus and others, why Astacus fluviatilis survived in the northern and western parts of Russia, as well as in the upper Danube, while in the Ponto-Caspian basin, generally speaking, it is already crowded out. Astacus leptodactylus is indeed a late comer: it hitherto retained the ability to live in salt water, which other species are already incapable of. It did not penetrate into the northwestern basins of Russia, since they were already completely separated from the Ponto-Caspian by the time this species was resettled, but with the establishment of artificial communication through channels it penetrates the northwest, as well as by transplantation (in the thirties merchant Fetosov and others) spreads over Siberia, the rivers of which are devoid of crayfish. However, the Irtysh is already inhabited by long-legged river crayfish.
Wide-legged crayfish, or European freshwater crayfish - Astacus fluviatilis = Astacus astacus Linnaeus, 1758,
Long-legged crayfish - Astacus leptodactylus Eschscholtz, 1823
Fat footed cancer - Astacus pachypus
West European Crayfish - Astacus torrentium = Austropotamobius torrentium
Eastern European Crayfish - Astacus nobilis
Astacus pallipes = Austropotamobius pallipes
The world production of crustaceans in 1997 amounted to about 1.3 million tons. A significant portion came from shrimp (940,000 tons, FAO, 1999). The total value is close to $ 8 billion. The production of freshwater crustaceans is much lower, about 170,000 tons ($ 870 million), of which 25,000 tons are freshwater crayfish. Approximately 69,000 tons of freshwater crustaceans are nonspecific (one specific species is absent during harvesting), and the bulk of the remainder falls on the giant river shrimp (Macrobrachium rosenbergii) (FAO, 1999).
Official international statistics underestimate the scale of production. According to J.V. Huner (personal observations, 2000), the total annual commercial collection of freshwater cancer exceeds 120,000 tons, and in some years reached 150,000 tons. In 1999, the People's Republic of China produced 70,000 tons, and the United States about 50,000 tons, mainly in the southern state of Louisiana. The latest figures, 30,000-35,000 tons per aquaculture. In 1994, the countries of Europe produced about 4,500 tons, of which only 160 tons came from aquaculture. In Australia, aquaculture produced 400 tons, but fishery catches are not reported.
The literature on the cultivation of European crayfish is scarce and controversial. Therefore, it is necessary to collect new data by interviewing as many experts in Europe as possible. For other regions, as well as for Europe, literature data is presented here. In addition, the article includes information from the conference of the International Association of Astacologists held in August 2000 (IAA, 2000).
The survey covers the following areas: 1. Cultivated species, 2. Annual production, 3. Juvenile production, 4. Average production, kg / ha, 5. Production technique, 6. Planting technique for cultivation, 7. Feeding and feed, 8 Diseases, 9. Predators, 10. Plants in the pond, 11. Water parameters.
Many reviews have been written about the cultivation of freshwater cancer - Wickins (1982), Huner and Brown (1985), Holdich and Lowery (1988), Morrissy et al. (1990), Huner and Barr (1991), Merrick and Lambert (1991), Lee and Wickins (1992), Westman et al. (1992), Holdich (1993), Huner (1994), and Skurdal and Taugbel (1994). But still, there are gaps in knowledge. This article covers the state of aquaculture of freshwater crayfish in Europe, methods and techniques used in the 1990s, and a comparison of the state of affairs with other regions of the planet.
Initially, three families of freshwater crayfish - Parastacidae, Cambaridae and Astacidae, respectively, were found on three continents (North America, Eurasia and Australia) and selected other regions of the world (Hobbs 1988). Not a single cancer has been found in Africa and most of Asia. The Parastacidae family is found in Australia, New Guinea, New Zealand, several regions of South America and Madagascar. Cambaridae, originally, were found only on the American continent. Astacidae primarily live in Europe, but also in the western United States (Figure 1).
Figure 1. The natural habitat (excluding European Astacidae) of the crayfish of the three families. The grid area is Astacidae, the horizontal lines are Cambaridae, the black area is Parastacidae. Hobbs, 1988
The number of native species varies greatly from continent to continent. Over 362 identified species and subspecies have been found in North America, most of which belong to the Cambaridae family (Huner and Barr 1991). More than 100 species of the Parastacidae family exist in Australia, South America, New Guinea, and Madagascar, and more recent information indicates an underestimation of these values (IAA, 2000). In Europe, 5 species of the Astacidae family were discovered (Hobbs 1988). And again, recent data from the Association of Astacologists indicate the existence of a larger number of species in Europe than previously thought. In total, there are 550 species worldwide.
Transfer and introduction of species to other continents and countries
Different types of crayfish have come to many regions of the world in order to cultivate and fill lakes and rivers. To replace populations affected by the American plague fungus (Aphanomyces astaci), American species were brought to Europe. The plague of crayfish came to Europe in 1860 (Figure 2). Later, Europeans began introducing into the contaminated waters species from the United States that were immune to the disease (Ackefors and Lindqvist 1994). By 1890, American striped cancer (Orconectes limosus) was introduced into Germany. In the 1960s, they began to introduce Signal Cancer (Pacifastacus leniusculus) into Sweden (Furst 1977), and in 1973 Red Florida Cancer (Procambarus clarkii) was introduced into Spain (Habsburgo-Lorena 1979, 1983a, 1983b). In 1983, the Australian species, Yabbi's cancer (Cherax destructor, C. albidus) was introduced to Spain (Gutierrez-Yurrita et al. 1999), but it did not have high economic significance. This species has also been introduced into Italian waters (D’Agaro et al. 1999), together with the Red-claw cancer (C. quadricarinatus).
Figure 2. Distribution of plague fungus, Aphanomyces astaci, in Europe. Ackefors (1989). These dates show the first years of the occurrence of the plague. In two countries, the plague disappeared some time after the first hit (a year in parentheses), and then returned again (second date)
Today, American striped cancer lives in 16 countries, Signal cancer in 21 countries, Red Florida cancer in 10 countries (Holdich et al. 1999). Signal cancer is grown in 13 European countries (Ackefors 1999). A detailed description of many cases of the introduction of foreign cancers into various European countries is given by Gherardi and Holdich (1999). Red Florida cancer is currently spread outside the US and Europe: in Central and South America, Africa and Asia (Huner 2000). At least one Australian species, Red Crab Cancer, has been introduced to the United States (Masse and Rouse 1993) and is thought to have potential for cultivation in the southeastern states (Rouse and Yeh 1995). An experimental cultivation of red crab cancer is taking place in Israel (Karplus et al. 1995). The People's Republic of China introduced three Australian species: Yabbi, Red Crab Cancer, and Blue Crayfish (Cherax tenuimanus) (Ackefors 1994, IAA 2000).
Cultivated species and production
Less than a dozen types of crayfish are common in culture and less than two dozen are commercial (Huner 1994). In the south of the USA, mainly in Louisiana, the main cultivated species is the Red Florida Cancer (Figure 3), as well as the White Crayfish (P. zonangulatus) (Table 1). The total aquaculture production of these two species in 1999 was 35,000 tons, of which 85% was Red Florida Cancer (Huner, personal observations, 2000). In the northern United States and Canada, Red Florida cancer and species from the genus Orconectus are grown in small quantities (Huner 1994). In Australia, the main producing species is Yabbi Cancer, which produced 250 tons in 1998/99 (Wingfield 2000). It is followed by Red Crab Cancer (Figure 4) - 79 tons and Blue Crayfish - 49 tons. Australian species are larger than those crayfish that are grown in other parts of the world, especially Red-clawed and Blue. These species dictate high prices and, therefore, good prospects for export. Based on the survey results, aquaculture in Europe mainly includes four species: two native species, Broad-toed crayfish (Astacus astacus, Figure 5) and Narrow-toed crayfish (A. leptodactylus, Figure 6), and two invasive species, Signal cancer (Figure 7) and Red Florida Cancer. In addition, small amounts of Yabbi and American striped cancers are introduced and cultivated. In 1994, cancer production in Europe amounted to about 160 tons, of which 40% were Red Florida cancer, 32% Signal cancer, 17% Broad-crayfish, 8% Narrow-crayfish, and Yabby 4% (Ackefors 1998). The main producing countries are Spain, Sweden, followed by Russia, Germany, Great Britain, France, Denmark and Finland.
Figure 3. Red Florida cancer, Procambarus clarkii, originally inhabited the southern United States. It is the most important cultivated species in the world. It is introduced in various countries of Europe, Asia and Africa. The usual commercial size of adults is 8–9 cm with a mass of 20 grams (photo Christoph Vorburger) Figure 4. Red claw cancer, Cherax quadricarinatus, a natural habitat located in the tropical zone of Australia. The most important cultivated species in the subtropical zone of western Australia. Introduced to Europe, China and North America. With the exception of North America, cancer production is low. The usual commercial size of adults is 14-20 cm with a weight of 40-100 grams. Pictured male, Upper Pier Reservoir, Singapore. Length - 176.4 mm, cephalothorax length - 65 mm. (photo by Tan Heok Hui). Figure 5. Broad-toed crayfish, Astacus astacus, lives in eastern Europe and parts of Turkey. This species is highly regarded and actively grown in Europe. Due to susceptibility to plague fungus, cancer populations have declined significantly. The usual commercial size of adults is 9-10 cm with a weight of 20-40 grams (photo by Nylund Viljo) Figure 6. The narrow-toed crayfish, Astacus leptodactylus, lives in eastern Europe and parts of Turkey. Due to the spread of plague fungus, cancer populations have declined significantly, especially in Turkey. The usual commercial size of adults is 9-10 cm with a mass of 20-40 grams (photo by David Holdich and Phil Hurst) Figure 7. Signal cancer, Pacifastacus leniusculus, lives in the western states of North America. Introduced to Sweden in the 1960s, it is now widespread in Europe and some other parts of the world. The usual commercial size of adults is 9-10 cm with a mass of 20-50 grams (photo Christoph Vorbuger and Phil Hurst)
Table 1.The main cultivated cancers in the USA, Europe and Australia
|View name||Trivial name|
|Procambarus clarkii||Red florida cancer|
|Procambarus zonangulus||White crayfish|
|Cherax destructor, C.albidus||Cancer Yabbi|
|Cherax quadricarinatus||Australian Red Crab Cancer|
|Cherax tenuimanus||Blue cancer|
|Astacus astacus||Wide-toed crayfish|
|Astacus leptodactylus||Narrow-toed crayfish|
|Procambarus clarkii||Red florida cancer|
|Pacifastacus leniusculus||Signal cancer|
Farmers crayfish prices
In Europe, prices for different types of cancers are very different. In Sweden, Broad-crayfish crayfish sets a higher price than Signaling crayfish, and they, respectively, are more expensive than imported deep-frozen Red Florida crayfish. Farmers sell Broad-crayfish for $ 40 / kg and Signal Cancer for $ 20 / kg. In the US, farmers sell Red Florida Cancer for $ 1-3 / kg, depending on the supplier. In Australia, Yabby cancer costs $ 3-4.5 / kg, Red-claw cancer costs $ 4.5–9 / kg and Blue Cancer costs $ 9–13 / kg (Wingfield 2000).
Production per hectare
In Europe, the maximum production of 1000 kg / ha of land is accounted for by Spain and the invasive American Signal Cancer. The northern countries, Sweden and the UK, grow Signal Cancer less than 50-680 kg / ha. Bulgarian farmers have been reported to grow 200-500 kg / ha of Narrow-toed crayfish. For broad-toed crayfish, production volumes range from 60 to 430 kg / ha in Sweden, 300-600 kg / ha in Germany. In the United States, Red Florida cancer production is highly dependent on the cultivation method. Huner (1999) reported the collection of this species 526 and 925 kg / ha in small and large ponds, respectively. In rotary rice crayfish systems, production varies from 450 to 2800 kg / ha (Caffey et al. 1996). Due to the warm climate and special conditions in the southern states of the USA, production volumes there are higher than in Europe. In Australia, Yabbi cancers are grown in the subtropical region, while Red Crab cancers are grown in the tropical region. The annual production of Yabbi is 700-2000 kg / ha (Wingfield 2000), and the red claw cancer exceeds 2000 kg / ha. The production of Blue Cancer, the largest cultivated one, can reach 1000-3000 kg / ha in semi-intensive ponds, while in common semi-extensive ponds the volume is about 1000 kg / ha (Swannel 1994).
There are five methods to increase the production of crayfish: 1. Management of wild populations, 2. Extensive production in natural and artificial ponds, 3. Semi-intensive cultivation in ponds and canals, 4. Intensive production in pools, aquariums and canals, 5. Systems in which the growing of crayfish and plant crops alternate.
In Europe, all the Red Florida crayfish produced in Spain were obtained through manipulation of feral populations, and therefore, in fact, do not come from aquaculture. FAO statistics, however, include data from Spain.
Crayfish are brought to rice fields or marshy areas, and they remain in burrows during droughts. Crayfish appear in the water when rice fields flood. A similar practice is common in the ponds of Louisiana, USA. In the latter case, open ponds are dug up to standard sizes of 4–8 ha, although there are also ponds with an area of up to 400 ha (Huner and Barr 1991). The large size of the reservoir allows you to streamline the collection using boats or traps. Modern ponds are equipped with internal deflector partitions that provide mixing of water. They are located at a distance of 50-76 meters from each other and are open from opposite ends. Closing the life cycle of Red Florida Cancer requires annual drainage of the pond.
Red Florida cancer is also cultivated in the United States in rice fields with rotation of rice and crayfish (Caffey et al. 1997). Rice is planted during March and April. In June, when rice reaches a height of 20–25 cm, 55–65 kg of adult crayfish per hectare is introduced into the field. In August, the ponds are dried and rice is harvested. In October, rice fields are replenished with water and crayfish are collected from November to April.
According to the survey, most countries in Europe dig earth ponds for growing crayfish. Water bodies usually have an area of 0.01-0.1 ha, but larger ones are also found. In many areas of Sweden, cylindrical ponds are currently common with small “islands” in the middle (Ackefors 1997). Their construction is cheap, because the excavator can quickly dig out, moving in a circle and scattering the soil on both sides. The pond consists of a shallow zone 1 meter deep in the middle around the island and a deeper zone along the outer edge (3-4 meters). To maintain production indicators, the reservoir should be drained and cleaned every year or every two years. Without purification, production volumes fall steadily. The broodstock is kept in reservoir trays, gutters, or small ponds. Ponds usually have an area of 10-20 m 2 and a depth of 10-50 cm. When the females are ready to lay their eggs, they are transferred to floating trays with a mesh bottom so that young individuals can leave their mother. For experiments, tanks and pools are usually used, but they are also common in intensive crayfish cultivation, very often small containers are used to contain individual individuals, in order to avoid cannibalism. Various mechanisms of cannibalism inhibition are tested: the same size of individuals, balanced food, populations in which individuals exhibit weak aggression (Karplus et al. 1995). Other researchers cut off the outer left side of the claw, perform a fingerprint surgery, and thereby prevent aggression among individuals (Gydemo and Westin 1993).
Ponds of 0.03–4.5 ha are used for semi-intensive crayfish cultivation in Australia (O’Sullivan 1995). In Europe, ponds have various sizes and shapes. A parallel arrangement of ponds 10–20 meters wide and 50–200 meters long is recommended (Merrick and Lambert 1991). Some reservoirs are V-shaped, 5-6 meters wide, 2-2.5 meters deep and 200-400 meters long. This type of pond is no longer recommended in Sweden (Ackefors 1997) because draining it easily leads to coastal destruction. Today, ponds typically have a rectangular shape of 5 ha (Ackefors 1994, Medley et al. 1994). Optimum ponds for growing Blue Crab are 0.05 ha ponds (Swannel 1994). Some Australian and European farmers have experienced water leakage from the bottom of the pond. It can be solved by covering the bottom of the reservoir with a plastic liner. This cannot be done in a very large pond due to the high cost of the film.
The technique for planting crayfish is only slightly different in European countries. Respondents answered the question, how many juveniles, adolescents and adults were planted per 1 m 2 or 1 meter of shore length, based on three size classes (50 mm TL). The landing density for crayfish of the smallest class ranged from 30 to 2000 individuals / m 2. The upper limit is too large and is accompanied by the loss of juveniles. Landing of adolescents and adults on 1 meter of shore length in different European countries varies from 5 to 30 individuals. For juveniles with a length of 20-50 mm, the landing density is 10-150 individuals per 1 m 2. Larger crayfish (> 50 mm) plant 1-15 individuals per 1 m 2. Denmark reported the landing of 8-10 and 4-6 individuals per 1 meter of coast for crayfish 20-50 mm and> 50 mm, respectively.
In Louisiana, USA, adult Red Florida crayfish 80-100 mm long are taken for landing. In order to produce 450-600 kg per 4000 m 2, 4 kg of crayfish are required to be planted, and it should be noted that 144 females should be in the 4000 m 2 area (Huner and Barr 1991). Since the ratio of males and females is normally 1: 1, for any ponds, 9 kg of crayfish per 4000 m 2 are suitable. When the cultivation conditions (environment) are not optimal, the crayfish are not planted for the next season. In Australia, special hatcheries are being built to increase the production of juvenile Yabby and Red Crab cancer (Merrick and Lambert 1991). Hatchery growing is essential when the industry is in its infancy. This situation occurred in the 1960s in Sweden, when the cultivation of Signal cancer was just beginning (Ackefors and Lindqvist 1994, Ackefors 1997). Currently, the production of juveniles is not necessary, because most farmers already have their own hatcheries.
Young Yabbi cancers can be raised at a high planting density (up to 100 individuals / m 2) when they are first released and their nutritional needs are limited. Within 2 weeks, they switch to active nutrition and exhibit increased aggression. If you do not reduce the landing density during this period, there will be a high mortality rate. In extensive dams, the density of landing of juvenile Yabbi provides 1-2 individuals / m 2, in semi-intensive ponds - 10-20 individuals / m 2. Blue crayfish is planted at the rate of 5-10 individuals / m 2, and Krasnoklesnevy - 10-15 individuals / m 2 (O’Sullivan 1995). Some farmers increase planting density by using onion string bags as shelter. In pools with very intensive growing conditions, planting density reaches 100-200 individuals / m 3.
Blue-crayfish farmers in Australia plant crayfish ponds from 0+ (young) to 15 individuals / m 2 (Swannel 1994). They also practice the Blue Cancer and Silver Perch (Bairdiella sp.) Polyculture, which has been proven effective.
It is well known that natural behavior and high survival are closely related to the presence of shelters, bottom structures, and suitable environmental and feed parameters. To some extent, predation can be avoided by installing shelters in a pond. Some European respondents noted that farmers use piles of stones, bricks, pipes, and slate as shelters. In Australia, used tires were used as shelters.
Some farmers use plastic strips 2-3 meters long and 50 cm wide, organized in bags. They can also then be used to collect crayfish. For shelter of juveniles, string bags for onions are most often used, but they are also suitable for adults (Ackefors 1994).
Respondents from 10 European countries provided information on what they consider to be important components of feed for crayfish (Table 2). Farmers in many countries feed crayfish with pieces of fish, plants, potatoes and carrots. Black alder leaves (Alnus glutinosa), cereals, pieces of meat, zooplankton and factory granules are also used. Particularly important respondents noted cereals, pellets and pieces of meat. In particular, cereals are considered as an important lump in Sweden and Hungary, and alder leaves in Norway, potatoes and carrots in the Scandinavian countries. In addition, the crayfish is fed with natural flora and fauna in the pond.
Table 2. Cancer feeding on farms in 10 European countries in the early 1990s. xxx, the component is used frequently, x, rarely used
|Carrots and potatoes||Plants||Alder leaves||cereals||Fish pieces||Meat pieces||Zooplankton||Granules|
The pellet composition of commercial feed is different, but some farmers in Europe use Aller Aqua feed made in Denmark (Table 7). Granular feeds for trout and poultry were previously used, but they were banned in Australia as well as alfalfa (O’Sullivan 1995).
In the United States, when cultivating Red Florida crayfish, feeding on natural vegetation, agricultural waste, feed crops, and auxiliary feeds is common (Huner and Barr 1991). Agricultural waste includes sugarcane residues, sugarcane filter cake and chicken manure. Feed crops include rice, millet, sugarcane, soybeans. The prepared feed is brought into the pond to the crayfish, which can lead to a significant increase in the mass of individual individuals. Crayfish also eat natural food in the pond, organisms living in detritus and plant material. As shown in the United States, fertilizing 100-150 kg / ha of an equivalent mixture of superphosphate, monoammonium phosphate and potassium nitrate stimulates rapid algae growth and increases pond productivity (Huner and Barr 1991). However, many farmers who previously fed crayfish with granulated feed for poultry and trout have now switched to special crayfish feeds. Alfalfa, lupine, hay and compost are used as top dressing in Australia (O’Sullivan 1995). Some farmers grow fodder crops at the bottom of the pond before filling them with water (Maloney 1993), among these crops are barley, strawberry clover, oats, rye, and kikuya.
Diseases and parasites
Respondents were asked to rate the severity of the cancer problem in their countries (Table 3). The severity of the disease was evaluated based on livestock losses or decreased productivity. Six different diseases / parasites were mentioned. Some of these infectious or parasitic agents acted directly and caused specific diseases, while others could have an indirect effect, weakened the animal and made it more susceptible to other infections.
Table 3. The significance of 6 diseases or parasites in the cancer culture of 10 European countries (1990s). 1. Aphanomyces astaci, 2. Fusarium spp. (Ramularia astaci), 3. Saprolegnia, 4. Thelohania contejeani, 5. Psorospermium haeckeli, 6. Branchiobdella spp.
|The country||The severity of morbidity and parasites|
|Bulgaria||3 (caviar stage)|
|Denmark||3 > 4 > 2 > 1|
|Finland||5 (A. astacus)> 1 (A. astacus, P. leniusculus)|
|Germany||4 > 6 > 5|
|Hungary||1 > 2 > 4 > 6|
|Lithuania||6 > 4 > 1 > 2|
|Norway||4 > 5|
|Russia||3 > 6 > 4 > 1|
|Sweden||1 > 5 > 4 > 2|
|Great Britain||1 > 2|
The "plague" of cancers caused by Aphanomyces astaci is a fungal disease, and all local European cancers are susceptible to it. Invasive Signal Cancer can also become infected with the fungus in suboptimal conditions and during stress, as reported by Finnish respondents (Table 3). The infectious stage of the parasite is the zoospore, which leaves the mycelium of the fungus and enters the cuticle of cancer. Other species of fungi are generally considered less dangerous, for example, the most famous Saprolegnia spp .. This fungus attacks caviar attached to females. Other species incite Spotted Disease. It is triggered by several species of the genus Fusarium, although it is often said that this disease causes Ramularia astaci.
Among parasitic diseases, Porcelain disease is the most famous. It is caused by the microsporidia of Thelohania contejeani. Another parasite, Psorospermium haeckeli, which previously had a mysterious taxonomic status, is now classified as a new clade of parasitic protozoa (Ragan et al. 1996). The commensal worm (Branchiobdella spp.) Is often found on the outside of the cuticle of Broad-toed crayfish and Signal crayfish. It is not dangerous for cancer if it is not attached to the gills. Table 3 clearly shows that the importance of specific diseases varies in different parts of Europe. Three, four countries see cancer plague as the most serious disease, while the other three consider Saprolegnia to be the most dangerous. Other diseases and parasites listed in Table 3 are marked as number one in some countries.
American cancers are usually carriers of the plague fungus, but have immunity to it, and therefore are immune. Huner and Barr (1991) mentioned microbial diseases, parasitic protozoa, endoparasite worms and invertebrate ectoparasites that infect Red Florida cancer and other species. They reported that in North America, due to the absence of a real incidence problem, little attention has been paid to this area.
Merrick and Lambert (1991) noted that the entry of pathogens, such as plague fungus, into Australia would have disastrous consequences. Limited research over several years has shown that Yabbi and Pigeon cancer are very susceptible to A. astaci (Unestam 1975). Merrick and Lambert (1991) referred to bacteria, fungi, protozoa, platyhelminthes, nematodes as parasitic and infectious agents. They concluded that Australian cancers are relatively disease-free, and strict quarantine measures are needed to prevent the invasion of exotic pathogens.
Twelve European countries reported the presence of predators in reservoirs with crayfish (Table 4). Young crayfish are hunted by Swimmers (Dytiscidae), dragonfly larvae (Aeschna grandis), various amphibians, perch fish (Perca fluviatilis), roach (Rutilus rutilus, Cypridae). Eels (Anguilla anguilla, Anguillidae), perch and roach prey on adolescents and adult crayfish.Among the birds of prey, gray heron (Ardea cinerea) can be noted, and among mammals, American mink (Mustela vison), otter (Lutra lutra) and muskrat (Ondatra zibethicus). Table 4 also lists random predators - waterfowl, domestic cats (Felis silvestris), and gray rats (Rattus norvegicus). Three or more countries of 12, as the main predators, named nymphs of dragonflies, eel, perch, gray heron and American mink.
Table 4. Predators of European cancer farms in the early 1990s. The numbers in brackets indicate the number of countries in which a predator is considered a serious problem. Information from 12 countries
|Class||Common predators||Rare predators|
|Insects||Swimmers (Dytiscidae) (2), Dragonfly Nymphs (4)|
|Amphibian||Water salamanders (2), Frogs and toads (2),|
|Fish||Eel (Anguilla anguilla) (6), perch (Perca fluviatilis) (4), roach (Rutilus rutilus) (1), pike perch (Lucioperca lucioperca, Percidae) (1)||Trout (Salmo trutta, Salmonidae), Pike (Esox lucius, Esocidae)|
|Birds||Gray Heron (Ardea cinerea) (3), Black Crow (Corvus corone) (1)||White Stork (Ciconia ciconia), waterfowl, duck|
|Mammals||American Mink (Mustela vison) (4), Otter (Lutra lutra) (2), Muskrat (Ondatra zibethicus) (2)||Domestic cat (Felis silvestris), Forest ferret (Mustela putorius), Common fox (Vulpes vulpes), Gray rat (Rattus norvegicus), Water rat (Arvicola terrestris)|
Dangerous predators in the US ponds for cancer are grebes (Podiceps spp.), Cormorants (Phalacrocorax spp.), Pelicans (Pelecanus spp.), Marsh birds, coots (Fulica sp.), Water shepherds (Rallus spp.), Seagulls (Larus spp.), Terns (Sterna spp.) And coastal birds (Huner 2000). Vegetation in a pond with crayfish gives seeds, corms, tubers, which waterfowl regale on. Otters (Lutra sp.), Alligators (Alligatoridae) and turtles (Chelonia) also eat crayfish (Huner and Barr 1991). In addition, unsolicited species of fish are common, against which poisons are used - antimycin B and rotenone. There are many invertebrates that are carnivores, predominantly attacking young crayfish. Farmers in the United States are puzzled by the struggle with the semi-rigid (Hemiptera, bugs), Coleoptera (Coleoptera, beetles), dragonflies (Odonata). Muskrats (Ondatra zibethicus) and nutria (Myocastor coypus) are herbivorous species that tend to dig into the coastal embankment of a pond (Huner and Barr 1991).
Ponds in which rice is cultivated for harvesting or as fodder for crayfish are particularly attractive to waterfowl. There are many control problems for these birds. One of the ways to solve the problem is to design a pond for recreational tasks, to obtain the right to shoot birds, and to receive additional income from the use of a reservoir as a hunting ground. Usually fencing a large body of water from unsolicited intruders is too expensive an event.
In Australia, where ponds are usually smaller than American ponds, they guard birds and rats with a net and corrugated steel net, respectively (Ackefors 1994). These animals are undesirable for farmers because birds eat crayfish and bring unwanted plankton and seeds with them, while rats destroy the plastic liner used to isolate the bottom.
Aquatic plants and farms
The most common plants in European ponds with crayfish are shown in table 5. Data obtained from a survey of respondents from 10 countries. A total of 17 species or genera were noted, among which the most common macrophytes were Ceratophyllum demersum, Elodea canadensis, Chara spp., Potamo-geton spp., Myriophyllum spicatum and Lagarosiphon major.
Table 5. Plants distributed on the cancer farms of 10 European countries in the early 1990s. 1. Ceratophyllum demersum, 2. Elodea canadensis, 3. Chara spp., 4. Carex spp., 5. Typha spp., 6. Potamogeton spp., 7. Alisma plantago-aquatica, 8. Phragmites sp., 9. Polygonum amphibium, 10. Green algae, 11. Myriophyllum spicatum, 12. Hippurus vulgaris, 13. Oryza sativa, 14. Lagarosiphon major, 15. Cladophora sp., 16. Lemna trisulka, 17. Nitella fragilis
|Bulgaria||1, 11, 14, 15, 16, 17|
|Denmark||1, 3, 11,17|
|Finland||1, 2, 4, 5, 6, 7, 8,15|
|Germany||2, 3, 11, 13, 14|
|Hungary||1, 5, 8, 9, 17|
|Norway||2, 3, 6, 10, 11, 14|
|Sweden||2, 3, 4, 6, 11, 12, 14|
In the United States, natural vegetation is found in most ponds. Local plants are allowed to grow during the summer in a pond, which is filled with water in the fall. Aquatic and semi-aquatic plant species abound in the pond with crayfish and persist for a longer period during winter filling with water than terrestrial species. Most often, they intentionally use Alternanthera philoxeroid (Alternanthera philoxeroides), ludwig (Ludviqia spp.) And highlander (Polygonum spp.). Sagittaria platyphous (Sagittaria platyphylla) and wild rice (Zizania aquatica) (Huner and Barr 1991) are also common.
In the Blue Cancer pond in Australia, Vallisneria spiralis and Sagittaria subulato are used. The former is more suitable because it grows in deep water and is better eaten by crayfish (Swannel 1994).
Growing crayfish, like all branches of aquaculture, requires good water quality, although some species (American striped crayfish) can survive in dirty water.
Production volumes are mainly affected by the temperature of the medium. In Europe, mild winters and cold summers in the west, very mild winters and hot summers in the south, cold winters and warm summers in the central part, very cold winters in the eastern part (Kendrew 1953). In July, the 21 ° C isotherm stretches from northern Spain to the northern Black Sea (Figure 8). The isotherm of 16 ° C stretches from the British Isles to the northern part of Finland, and the isotherm of 10 ° C - from Spain to the Cape Nordkapp, Norway, and passes through the northern part of Russia. Thus, the prerequisites for engaging in the cultivation of cancers in Europe are very different. Broad-crayfish crayfish have been shown to require 3 months and an average water temperature above 10 ° C to establish a stable population, with the exception of running water, rivers where it can survive and breed in cold conditions (Abrahamson 1972).
Figure 8. Isotherms of 10 ° C, 16 ° C, and 21 ° C for July in Europe, according to Kendrew (1953). Added values for the current observation. The top number for specific countries shows the number of months with temperatures of 10 ° C or higher on cancer farms. Similarly, the bottom digit shows the number of months with temperatures above 20 ° C
In Louisiana, where the main US cancer farms are located, the climate is subtropical. Summer temperatures are 25-30 ° C, winter - about 10 ° C. In tropical Australia, temperatures are 25–33 ° C throughout the year. Red claw cancer is currently cultivated in a subtropical climate (at the latitude of Brisbane), where the temperature rarely drops below 20 ° C (max. 30 ° C). Yabbi crayfish are grown in the subtropical zone, where the minimum water temperature is 10 ° C and the maximum summer temperature is 20-30 ° C. In Western Australia, where Blue Cancer is grown, the maximum temperature in summer is 30 ° C, and the minimum rarely drops below 10 ° C.
Temperature affects growth rates and biological processes such as egg incubation and molting. The survey allowed us to determine the number of months when the water temperature exceeds 10-20 ° C. In Europe, the number of months when the temperature exceeds 10 ° C is 4-5 in Sweden and Finland, 7.5 in Denmark, 6-7.5 in western Europe, 7-11 in central Europe, 7 in eastern Europe and 12 in southern Europe. The number of months when the temperature exceeds 20 ° C is 4 in Italy, 3-4 in central Europe, 1-2 in most other countries, with the exception of Great Britain and Finland, where such entire months rarely occur (Figure 8). In the United States and Australia, temperature conditions in areas where crayfish are grown are more stable than in Europe.
The second basic abiotic factor is the pH value. Over the past 30 years, European surface waters have been acidified. It is well known that the pH of water affects the productivity of freshwater aquaculture. Acid rains occur in a significant part of western, eastern, and central Europe, which adversely affect the environment (Alcamo et al. 1990, Hettelingh et al. 1991). Soils and bodies of water with low alkalinity are most susceptible to acidification, especially in Scandinavian countries (Chadwick and Kuylenstierna 1991, Hettelingh et al. 1991, and Kamari et al. 1992.). Low pH water is one of the main problems in growing cancers. It also causes problems for the natural cancer population.
Red Florida cancer can live in very alkaline water (pH 10) and acidic water (pH 5.8) (Huner and Barr 1991). It survives for several weeks at a salinity of 20 ppm, although in nature they cannot be found in water with a salinity of more than 8 ppm. Cultivation is carried out in fresh water. Recommended cultivation parameters in the pond are given in Boyd (1982), where the pH range is 7.5–8.5 for freshwater species, i.e. most European cancers.
It is difficult to put together most of the water parameters selected by respondents. In addition to temperature and pH, important factors are the concentration of calcium, iron, aluminum per 1 liter of water, as well as the presence of humic acids. Among the responses of respondents in Europe, the significance of the concentration of calcium and iron, and the pH level is very different.
Therefore, it is difficult to design a range of acceptable values. Ranges for Ca 1-150 mg / L, Fe 0.05-1.1 mg / L, pH 5.0-8.5. There was no information on the concentration of aluminum. Aquaculture in Finland and Sweden takes into account the presence of humic acids in water.
Is the survey a reliable source of information?
Answers were received from 22 respondents from Europe, all of whom are knowledgeable and experienced researchers and managers. Sixteen of them provided information on commercial and / or experimental growing of crayfish.
Referring to questions in the “Introduction” part of the survey, 16 respondents gave 57% (average) of answers, which is considered a satisfactory result. This level of response provides a good picture of the current state of aquaculture of cancers. Respondents from six countries indicated their lack of cancer farms. Respondents from the other two countries did not answer, but according to the authors of this article, these countries do not have cancer farms.
Literature review on the biology and ecology of cultivated cancers
Freshwater cancers are cultivated in temperate, subtropical and tropical climatic zones. To compare ecology and biology, the author compared the characteristics of two cold-water species, Broad-fingered crayfish and Signal cancer (both from Europe), two subtropical species, Red Florida cancer (Louisiana, USA) and Yabbi (Australia), and one tropical species, Red-claw cancer (Australia ) (Table 6). Data from Ackefors and Lindqvist (1994) for the first two species, from Huner and Barr (1991) and Huner et al. (1994) for Red Florida Cancer, from Merrick and Lambert (1991) and Wingfield (2000) for two Australian species.
Table 6. Biological and environmental characteristics of freshwater crayfish in a semi-intensive culture. Data from Ackefors and Lindqvist (1994) for the first two species, from Huner and Barr (1991) and Huner et al. (1994) for Red Florida Cancer, from Merrick and Lambert (1991) and Wingfield (2000) for two Australian species
Obviously, cold-water species grow much slower than warm-water types of crayfish. They reach maturity at an older age, and the incubation period for eggs lasts longer. Cold-water species mate once a year, while subtropical and tropical species breed several times a year.
The volume of production per hectare is much lower in cold-water species because of their slow achievement of the maximum size. Since cultivation technologies do not differ significantly, it can be concluded that productivity per unit area of the farm is higher for subtropical and tropical species than cold-water species.
Intraspecific and interspecific competition
Laboratory work showed aggression and cannibalism of cancers in relation to each other. This behavior is difficult to confirm in the field. One of the reasons is the dispersal of individuals over a large area, however, in itself, this circumstance is the result of aggressive behavior (Skurdal and Taugbel 1995).
Interspecific competition is clearly shown by Mackeviciene (1999). The author investigated the physiological and biochemical parameters of local Broad-toed crayfish and Narrow-toed crayfish, and exotic Signaling cancer in Lithuania. The highest level of steroid hormones, testosterone and corticosterone, which regulate the processes of growth, reproduction and adaptation to environmental changes, was noted in Signal cancer. This fact underlines the competitiveness of invasive species (Mackeviciene 1999).
In Sweden, in the field, it was found that Signal cancer not infected with plague fungus wins in competition with Broad-toed crayfish over 20 years of observation in the lake (Svardson et al. 1991). Similarly, Mackeviciene and Terentjev (1993) reported that Broad-cawed crayfish is gradually losing its ecological niche to Signal Cancer. Experiments have also confirmed this observation (Soderback 1991, 1993).
For indigenous species, Cukerzis (1988) showed that Narrow-toed crayfish has a wider adaptive range with an increased growth rate, fecundity, and better feed conversion than Broad-toed crayfish. It is concluded that Signal cancer wins the competition from the Broad-toed and Narrow-toed crayfish, and the Narrow-toed crayfish, in turn, wins the competition from the Broad-toed crayfish.
Crayfish feeding sometimes leads to a change in the composition of macrophytes in the pond and, after several years, all macrophytes may disappear (Ackefors 1997). Experiments with Signal and Broad-toed crayfish have shown that both species prefer common Haru (Chara vulgaris) to other plant species (i.e. Elodea canadensis, Scirpus lacustris and Potamogeton natans) (Nystrom and Strand 1996). Overgrown populations of S. lacustris and P. natans crayfish never eat, with the exception of young shoots of P. natans.
Nystrom et al. (1996) showed that the effect of crayfish on macrophytes depends on the density of crayfish, and on low (L) or high (H) alkalinity in the pond. Potamogeton natans and E. canadensis predominate in a pond with high alkalinity, where cancer thrives, while P. alpinus predominates in a pond with a low density of crayfish. Myriophyllum alterniflorum and P. natans prevail in the pond with low alkalinity and a large number of cancers, while the composition of E. canadensis and P. natans dominates in ponds with a small number of cancers. Species Alisma plantago-aquatica and Sparganium emersum are also common in reservoirs with a low density of planting crayfish. Nystrom et al. (1999) in experimental conditions found that cancers selectively eat macrophytes, reducing the Chara biomass relative to Elodea. Signal cancer, in general, has a stronger effect on macrophyte biomass than Broad-fingered crayfish.
Ackefors (1997) reported that some farmers in Sweden are working to eradicate E. canadensis by preventing the growth of shallow ponds (1-2 meters deep), while farmers who grow deep ponds (3-4 meters) consider this plant valuable a food source for cancer.
The alga Cladophora glomerata with a dense carpet covers the surface of many ponds and pools, and in some cases, by some farmers in Sweden, it is considered as a very useful species, for example, many young crayfish can be found attached to it. Therefore, algae is a shelter for crayfish. It floats on the surface in the daytime, because it releases oxygen, and drowns at night.
The survey did not include the question about the most useful plant species. However, in Sweden, personal experience and data from farmers indicate a preference for Chara sp. all other species, although Ceratophyllum, Myriophyllum, and Nitella are also considered valuable (Ackefors 1997). Some farmers also love cattail (Typha). Crayfish use cattail as a shelter and eat microscopic algae growing on its stems.
- The total aquaculture production of freshwater crayfish in the world is less than 40,000 tons, while the total production, including fishing, is 120,000-150,000 tons.
- Many types of cancers have been transferred to other countries for cultivation.
- In Europe, North American cancers have been introduced to replace indigenous species that are susceptible to plague fungus (Aphanomyces astaci).
- The main technology for growing crayfish is to dig ponds of various sizes.
- It is common to feed crayfish with pieces of fish, carrots, potatoes, cereals, plants and pellets. In addition, in order to increase the productivity of ponds and develop natural forage in it, fertilizers are added.
- In Europe, the main disease problem is related to the plague fungus from North America.
- Invertebrates and fish are predators in relation to juvenile crayfish, fish, mammals and birds are the main predators in relation to adult crayfish.
- Cannibalism is common among crayfish; it impedes the growth of crayfish in conditions of high planting density.
- The annual production of crayfish per unit area is much greater in a warm climate than in a cold one.
- Water in a pond with a relatively high concentration of calcium (> 20 mg / L) is preferred for the cultivation of cancers.
- Most cancers are susceptible to turbid water, pH 0.1 mg / L.
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