BIOLOGICAL FEATURES OF HERBIVOROUS FISH
Silver carp (Hypophthalmichthys molitrix Val.). In the pond polyculture of the southern regions of Russia (IV-VI zones), silver carp ranks second after carp in terms of production volume. Belongs to the carp family. Its homeland is the rivers of Central and Southern China. Within Russia it lives in the river basin. Cupid. Under natural conditions, it reaches a weight of 30-40 kg. The fish is schooling, occupies the upper and middle horizons of the pond water, is more thermophilic than carp, the optimum for growth and intensive feeding is at the level of 25-30 ° C. Keeping ponds with lower water temperatures, for example, 17-23 °C, which is typical for the Central and Northern regions of the Russian Federation, significantly slows down the growth and development of silver carp. At this temperature, at the age of two, it reaches a weight of about 200 g. In the south of the country, silver carp matures at 3-4 years of age, in the northern regions (I - II fish farming zone) - at 7-8 years. In natural reservoirs, spawning occurs during the flood period in the river bed on deep rifts with a rocky bottom at a water temperature of 20-25 ° C and above. Fertility - up to 1 million eggs or more, depends on the age and weight of the female. The diameter of the eggs is 1.1-1.3 mm, after fertilization and swelling it reaches 3.5-5.0 mm. Fertilized eggs develop during the period of drift in the upper layers
river water.
The embryos hatched from the eggs continue to drift until the larval stage begins and the transition to active feeding. Subsequently, the larvae migrate to the coastal zone and to
shallow bays where they feed and grow. From spawning to the release of embryos from the eggs at a water temperature of 24-25 ° C, it takes about 4 days. During the first days and weeks, the juveniles feed on zooplankton. After reaching a length of 1.5 cm or more, the main food of silver carp becomes phytoplankton and detritus. Favorite foods are diatoms and green algae; blue-green algae are less consumed. In ponds, when carp are intensively fed with compound feed, it actively filters out small and dusty particles of food that have become inaccessible to the carp. The feeding of silver carp on phytoplankton is due to the structural features of its gill apparatus, which has a mesh plate with holes of 20-25 microns on the gill arches.
Motleysilver carp(Aristichthys nobilis Rich.). The bigheaded silver carp is a large and strong fish, belongs to the carp family, and naturally lives in the rivers of Southeast Asia and in the river. Cupid stays in the middle layers of water in a dense school. Schooling also persists in pond conditions.
In pond polyculture under the conditions of zone III of fish farming, bigheaded carp takes second place, and in zones IV - VI it takes third place in terms of production volume, it is thermophilic, the highest growth rate is observed at a water temperature of 25-30 ° C. In the temperature conditions of central Russia and further north, if there is a sufficient amount of food, it grows faster than silver carp; two-year-olds reach 300-400 g.
In southern conditions, bighead carp matures in the 6-8th year of life. Fertility is about 500 thousand eggs, in some individuals - up to 1 million eggs or more. Spawning occurs in the same way as for silver carp, at a water temperature of 20-24 °C. The feeding pattern is determined by the structure of the gill filtering apparatus, in which the cells are approximately 2 times larger than those of the silver carp. The distance between the points
adults are 40-60 microns. The diet of bighead carp is dominated by zooplankton, the proportion of which in the diet reaches 50% or more, detritus and large forms of phytoplankton. By the nature of its feeding, it is a competitor of carp (especially fingerlings) in consuming zooplankton. This limits its production in pond polyculture.
Hybrid of white and bighead carp. In fish farming zones I and II, due to the relatively low water temperature and slow growth of the original species of silver carp, it is recommended to grow their hybrid. The biological characteristics of the hybrid differ little from the original species. A silver carp hybrid has characteristics of each parent. The gill apparatus of the silver carp hybrid acquires the ability to filter out both small and large microalgae and zooplankton. With a lack of zooplankton, hybrids switch to feeding on phytoplankton and detritus and outstrip bighead carp in growth. In addition, silver carp hybrids have increased vitality.
Hybrids have a lighter color compared to bighead carp. The keel of the hybrid is longer than that of the motley and continues to the head beyond the ventral fins. It is more difficult to distinguish a hybrid from a silver carp, since they have much in common in color and shape, but the keel of the hybrid is slightly shorter and does not reach the interbranch space. In addition, the keel of the hybrid has a less acute angle than that of the silver carp. The hybrid has retained the ability to live and feed in the water column, which makes it possible to catch it with conventional straining fishing gear. By eating phytoplankton, zooplankton, detritus and the remains of the dusty fraction of carp feed, the silver carp hybrid, like the original species, cleans the pond of excess organic matter, thereby performing the function of a biological ameliorator.
Grass carp (Ctenopharyngodon idella Val.). This is a fast-growing fish that feeds on higher aquatic vegetation (macrophytes). Under natural conditions, it reaches a mass of 32 kg, but the growth rate largely depends on the water temperature and the presence of vegetation. The optimum temperature for grass carp is within 25-30 °C.
In the Moscow region, grass carps mature at the age of 9-10 years, in the south of the country - at 5-6 years. Fertility reaches 700 thousand eggs or more. The biology of spawning is the same as that of silver carp. After fertilization, grass carp eggs swell quickly and have almost the same density as water, which creates buoyancy. Egg development occurs while drifting along the river in a suspended state. Embryos hatched from eggs
continue to develop in flowing water, and after a while they enter quiet backwaters and shallow waters, where they feed intensively. Temperature requirements are similar to silver carp.
When grown in ponds, grass carp completely suppresses the development of higher aquatic vegetation for two to three years, while at the same time actively consuming carp feed, while paying poorly for it. Therefore, the standard planting density of these
fish in pond polyculture is small, and fish productivity is limited to 40-110 kg/ha, depending on the presence and development of macrophytes.
It should be noted that only grass carp and silver carp are completely herbivorous, and then with certain assumptions, since at different periods of life and in different situations they can feed on zooplankton, detritus, mixed feed, etc.
FEATURES OF CULTIVATION OF HERBIVOROUS FISH
OBTAINING MATURE SEXUAL PRODUCTS
In the conditions of fish farming zones V - VI, female silver carp mature at the age of 3-4 years, bighead carp - 4-5 years, grass carp - 4 years. Males mature a year earlier. Due to the fact that the fertility of first-maturing females of all three species of herbivorous fish is two times lower than that of re-maturing females and the eggs and larvae are much smaller than those of older spawners, the use of first-maturing individuals for breeding purposes should be avoided. Female silver carp should be used at the age of 5 yearlings, bighead carp - 5-6 yearlings, grass carp - 5 yearlings. Males of all three species are transferred to breeding grounds a year earlier.
Good results are obtained when using females aged 6-8 years in the 2-4th year of operation. Manufacturers older than 10-12 years should not be used.
The fish selected for the production of offspring are sorted by species, sex, groups and, taking into account age, are placed in ponds for pre-spawning housing of spawners. The area of each such pond is 0.05-0.5 hectares, depth is 1.0-1.5 m. With the establishment of a stable average daily water temperature in these ponds within the range of 19-20 ° C, work begins on obtaining sexual products from herbivorous fish. The duration of the spawning campaign should not exceed 25-30 days.
To catch spawners, pre-spawning ponds are lowered, the individuals most ready for spawning are selected and, using nets, placed in stretchers with water or canvas vats installed on vehicles. Planting density up to 100 kg/m3. Fish sorted to obtain reproductive products are kept in spawning cages or containers. The dimensions of the canvas container are 1.55x0.6x0.7 m, water consumption is 0.2 l/s, planting density is no more than 2 producers per container.
To stimulate the maturation of reproductive products, acetonated pituitary glands of carp, carp, bream, catfish and choriogonic gonadotropin are used. Hormonal drugs are administered to producers along with an antibiotic (mainly penicillin) to prevent inflammatory processes and fish death.
Injections are carried out in a stretcher with water. The pituitary substance or choriogonin is administered to manufacturers in the form of an aqueous suspension prepared immediately before injection. To prepare the suspension, the pituitary glands are thoroughly ground in a porcelain mortar. For injection, a mixture of pituitary glands of different weights is taken. The volume of the pituitary gland suspension ranges from 1.5-2.5 ml. The injection is made into the back muscles above the lateral line, but slightly below the base of the dorsal fin. Hormonal injections stimulate the maturation of oocytes only in the completed stage IV of maturity (subphase E2).
To achieve the effect of maturation of females, fractional injections are used, the first (preliminary) and the second (permissive). Males are given the injection once. At the beginning of the spawning campaign, the time between injections to females is 24 hours; at the end, when the average daily water temperature is above 24 °C, the dose of pituitary injections is reduced by 2 times, and the time between them is reduced to 12 hours.
The first dose of pituitary injections for females is 0.5-0.8 mg/kg, the second - 4-8 mg/kg. For males - 1.0-1.5 mg/kg. The first dose of choriogonic gonadotropin for females (effective only for silver carp) is 0.2-0.4 thousand IU/kg, the second - 2.0-2.5 thousand IU/kg. For males - 0.75-1.0 thousand IU/kg. The activity of choriogonic gonadotropin is 500: 1 (ME: 1 mg pituitary gland). The antibiotic, together with the pituitary suspension, is administered intramuscularly with each injection in the amount of 50 thousand IU per fish. The volume of suspension for preliminary injection is 0.5-1.0 ml, for resolving injection - 1.0-2.0 ml. Males are injected 1 hour before females are injected. The water temperature must be at least 20 °C.
The biological meaning of fractional injections is that the first dose of the hormone causes a displacement of the nucleus in the oocytes, which, before the second injection, is closely adjacent to the nuclear membrane. The second dose causes nuclear transformation, ending with ovulation - the release of eggs from the follicular membranes. The first dose of the hormone promotes pre-ovulatory changes in oocytes and turns them into mature eggs, the second dose promotes ovulation.
After injection, the spawners are placed in spawning earthen cages or maturation pools, the stocking density is one spawner per 1 m 3 . Water consumption per 100 kg of fish should be 6 l/s, oxygen content not less than 5 mg/l, water temperature 20-25 °C. The maturation of females after pituitary injections is 80%.
The duration of maturation of females, depending on the water temperature after pituitary injections, decreases at temperatures from 20 to 27 °C from 13 to 6 hours, i.e., with an increase in water temperature by 1 °C, the time of female maturation decreases by 1 hour.
When using choriogonic gonadotropin, the time of maturation of females increases by 1-2 hours. Accurate determination of the time of maturation of females is very important, since overexposure of ovulated eggs in the body cavity of a fish for 30 minutes reduces its quality by 60%, and after an hour, the mortality rate during incubation reaches 96%.
About an hour before oocyte maturation, the readiness of females is checked. When catching females, spawning cages or pools are lowered, maintaining flow at low water levels. Caviar is obtained in a dark place or under a canopy. The fish are thoroughly wiped from the water with gauze, and the eggs from each female are filtered separately into dry, clean basins. Mature caviar flows freely from the body cavity of the fish. High-quality caviar has little ovarian fluid and its color ranges from grayish-blue to bright orange. Overripe eggs contain a lot of ovarian fluid and some eggs are cloudy white.
When herbivorous fish are reproduced in a hatchery manner, in contrast to carp, there is a significant post-spawning death of producers, especially silver carp. With a planned normal mortality of spawners of 20%, more than half often die, while some of the surviving fish have decreased fertility and become barren. The death of producers of herbivorous fish occurs mainly for two reasons: trauma and the use of immature or overripe females.
Traumatization of fish occurs both during fishing and during the injection and straining of caviar and milt. Injured areas of the body get infected, resulting in acute inflammatory processes, which are especially intense at a water temperature of 25-28 ° C. It is possible that the inflammatory process also occurs from the introduction of foreign pituitary protein into the fish’s body, especially when split injections are used.
The use of immature females, physiologically unprepared for spawning (having gonads in the incomplete IV stage of maturity) or overripe ones, in which the processes of resorption of unspawned mature oocytes have gone far, leads to the fact that in such females a small part of the oocytes are ovulated during pituitary injections. As a result, ovulated eggs appear in the gonads, which cannot be swept out by the fish or strained by the fish farmer. These eggs, having lost contact with the body, undergo rapid decay, which leads to the death of the fish. Already after the first injection, such females experience clouding of the eyes, and hernial protrusions of part of the ovary from the genital (genital) opening often appear. To avoid the use of females that do not mature after pituitary injections and to significantly reduce the death of fish during the spawning campaign, it is necessary to carefully carry out spring grading, and work on obtaining offspring in a short time.
To prevent injury to spawners, it is necessary to use earthen spawning cages with hidden hydraulic structures, catch fish using tarpaulin hoses, and use anesthetic drugs. An effective remedy that minimizes inflammatory processes in producers is the use of penicillin. The introduction of penicillin does not affect the timing of maturation of females and the quality of offspring.
INCUBATION OF CAVIAR
30-60 minutes before receiving caviar from females, milk is collected. The male's abdomen is thoroughly wiped with dry gauze and the milk is strained into dry, clean glass bottles. You cannot mix milk from several fish in one container. Sexual products are stored in wide-mouth thermoses with ice or in refrigerators. When milk is stored for 10-12 hours, the fertilizing ability of sperm does not decrease.
To determine the quality of sperm, a small amount of milk is applied to a glass slide, a drop of water is placed nearby and the two are connected. The movement of sperm cells is observed under a microscope using a 7x eyepiece, 8x or 40x objective lens with the condenser diaphragm closed. In high-quality milk, the movement of sperm continues for 15-30 seconds or more. The warmer the water, the shorter the life of sperm.
Insemination of eggs from each female is carried out using a dry method with previously prepared milk from 3 males, or the milk is immediately expressed onto the eggs. The milk is carefully spread over the caviar with a bird's feather and mixed. A little clean water is added to the mixture of caviar and milk and mixed again, at which time the eggs are fertilized. After 1-2 minutes, fresh water is added to the basin with fertilized eggs, mixed and the water is drained. This operation is repeated 1-2 times. Lumps of mucus, blood and scales are removed with water. After washing, the eggs are placed in incubators.
The most common are VNIIPRH devices with capacities of 50, 100 and 200 liters and their modifications - IVL-2 and "Amur". The performance characteristics of the devices are given in Table 20.
Table 20
Amount of loaded caviar and water consumption
The devices are loaded 5-10 minutes after fertilization of the eggs. The eggs from each female are placed in a separate apparatus, the water in the apparatus is drained to 20-30 liters, the eggs are placed, and the water supply is turned on in operating mode, which ensures mixing of the eggs throughout the entire volume. Labels are placed on the devices indicating the type of fish, the time and date of receipt of reproductive products, and the amount of eggs laid.
As the eggs swell and increase in volume, water exchange is adjusted to a value corresponding to the type of apparatus; the eggs should constantly be in slight movement. 1.5-2 hours after laying, the percentage of egg fertilization at the stage of 4-8 blastomeres is determined. To do this, about 100 eggs are viewed under an MBS-1 binocular microscope and the number of normally developing eggs is counted. Benign caviar
fertilized at least 90%.
3-5 hours before hatching, 100-150 eggs are examined under a microscope and the percentage of abnormally developing embryos is determined. When incubating eggs with 90% fertilization, 10% deformities and 15% waste of low-quality fertilized eggs are usually noted; survival rate during the incubation period is 65%.
During the incubation of eggs (the oxygen regime must be at least 4.0 mg/l), an optimal water exchange regime is maintained; dead eggs are collected using a siphon, which is concentrated in the form of a cloudy white layer above the live eggs. The selection of dead eggs is carried out after completion of gastrulation, at a water temperature of 22-26 ° C, 12-13 hours after fertilization. At the optimal water temperature for incubation of 21-25 °C, single embryos hatch first, after 30-60 minutes mass hatching occurs, which continues for 10 hours. After hatching, free embryos rise to the surface and are carried out of the apparatus by a current of water. When using VNIIPRH devices for incubation of eggs, the hatched embryos are sent through hoses to the IVL-2, "Amur" or "Dnepr-1" devices, which in such a situation are used for incubation.
When eggs are incubated in these devices, the hatched embryos are kept in them. During aging, mesh inserts are installed in the apparatus and the water supply is turned on. For aging, you can use small cages made of nylon sieve. After the embryos hatch, the walls of the apparatus inserts are filled with membranes, which are carefully removed. After a few hours, the remaining shells dissolve in water and are carried down the drain. After 2-3 days, the walls of the cages and inserts are cleaned of silt deposits. By taking daily samples, the approximate time period for the larvae to switch to a mixed diet is determined.
After switching to mixed nutrition, they begin transporting the larvae. 2-3 hours before shipment, the number of larvae is taken into account by counting 2-3 samples (200-300 ml of a mixture of larvae with water) and converting to the total volume of the holding tank, recalculated per apparatus.
The larvae are transported in plastic bags. 10 liters of water are poured into a 40 liter bag and 80 thousand pieces are placed. larvae, filled with oxygen and closed with a clamp. Packages for 30 min. left in the shade. During this time, it is determined whether there is any leakage from the water and oxygen bags. Next, the packages are placed in cardboard boxes and loaded onto a vehicle. When transporting up to 24 hours, 50 thousand pieces are placed in bags. larvae The age of the transported larvae is 3-5 days. During transportation of larvae, sudden temperature fluctuations above 30 °C and below 15 °C are unacceptable, as well as transportation on bad roads and in unsuitable transport.
Underwater reclamation fish (herbivorous fish)
The shallow waters of reservoirs, lakes, estuaries, canals and ponds are heavily overgrown with underwater and surface vegetation in the summer. A lot of algae appears in reservoirs. The water “blooms”, becoming completely green. Excessive overgrowing of water bodies with algae and grass is harmful to most fish; it contributes to swamping of lakes, ponds, estuaries and canals. We have to clean water bodies, and this takes a lot of effort and money.
Excessive overgrowth reduces the productivity of fish ponds and reduces the capacity of irrigation canals.
Thus, in Rhodesia, on the Zambezi River, during the construction of the Caribbean hydroelectric power station, a large artificial lake was created. Suddenly it began to become overgrown and in places so thick that it became possible to walk on it without getting your feet wet. These thickets are increasingly advancing on the reservoir and have already captured a significant part of it.
In our country, algae aggression has not yet reached such proportions, but still often causes significant damage.
Thus, due to the overgrowth of the Karakum Canal in a 9-kilometer section, at one time the daily flow decreased by such an amount of water that would be enough to irrigate 20 thousand hectares of cotton crops!
When reservoirs used as coolers for thermal power plants become overgrown, electricity generation decreases, and sometimes more serious operational difficulties arise.
Overgrowing of ponds also leads to a strong decrease in their fish productivity. Finally, the “blooming” of water, that is, again, overgrowing, entails a decrease in the quality of drinking water.
In the fight against aquatic vegetation, special water mowers are used and they are poisoned with herbicides. And now, in many ponds, reservoirs and canals, fish - grass carp and silver carp - have become faithful assistants to fish farmers and irrigators.
The benefits of using algae for growing fish can be very great. After all, their reserves in our waters are many times greater than all other food resources for fish.
Nature is often unfair regarding the distribution of fish in water bodies. For example, in the ponds and lakes of Ukraine and the southern regions of the USSR there is a lot of aquatic vegetation, including algae, which are happily eaten by grass carp and silver carp fish, which previously lived only in the Amur River.
This injustice of nature is being corrected by fish farmers: “reclamation agents” are now transported to reservoirs in different geographical zones of the USSR, and in new places, herbivorous fish perform the work of reclamation agents, one might say, conscientiously: where they are bred in large numbers, they leave behind them in dense thickets entire clearings, like brigades of mowers.
Some fish have various nicknames - names of animals. For example, carp is called a water pig because of its fat content and omnivorous nature. And there is also a fish called the water goat. This is how the silver carp was called in China. This name is given because the silver carp, like a goat, “grazes” - it eats large quantities of algae. In this regard, along with grass carp, it is the only fish of its kind that can be of great benefit in overgrown reservoirs, acting as a land reclamation agent. This amazing fish feeds mainly on microscopic algae - phytoplankton, of which a huge amount appears in our reservoirs in the summer.
But the value of silver carp lies not only in this; it is, first of all, a valuable commercial fish, easily acclimatized.
Silver carp is a large fish, up to a meter long and weighing up to 8 kilograms or more.
Its back and upper part of its head are greenish-gray, and its sides and belly are silvery. The dorsal and caudal fins are colored the same as the back, and the other fins are light, slightly yellowish. The iris of the eye is silvery.
Silver carp is common in the rivers of East Asia, from the Amur in the north to the rivers of Southern China in the south. It is absent in the rivers of Korea. In the r. The Amur silver carp is common in the middle and lower reaches.
Silver carp is distinguished by some features that are determined by the feeding pattern of this herbivorous fish, primarily by the structure of the pharyngeal teeth: they are strong and flat, adapted for flattening algae.
Its intestines are extremely long - fifteen times longer than the entire body. The head is large, so in the Far East it is called big-headed. The silver carp has a well-developed gill apparatus; Numerous gill rakers form a kind of thick filter that traps the smallest algae and floating particles in general.
Over a thousand years ago, silver carp was appreciated in China and began to be grown. It grows well in ponds, and therefore has long been an object of fish farming.
Silver carp are also bred in Taiwan and Siam. Silver carp fry are caught in rivers and then raised to market weight in ponds.
Since in the reservoirs of the European part of the USSR there are no fish that consume plant food, silver carp serves as an excellent object for breeding in our reservoirs.
For spawning, which occurs in the summer, silver carp ascends the river. Puberty occurs at the 5th - 6th year of life. Males mature earlier than females. After spawning, it goes into lakes and small channels with a sufficient amount of algae. Silver carp spawns when the water rises, its turbidity increases and the temperature is 26 - 30°. In spawning areas, the water flow is very fast. This fish spawns in the surface layers of water. In China, silver carp spawn from April to July, and the main spawning occurs from May 20 to the first ten days of June. Spawning is portioned. Most often, a female is followed by two males. Spawning usually occurs in the morning.
The female silver carp spawns up to half a million pelagic eggs with a diameter (after swelling) of 3.5 - 4.5 millimeters.
At a temperature of 25 degrees, after two days the eggs hatch into embryos 6 millimeters long. At first they lie at the bottom, occasionally floating up into the water column. At the age of 7 days, the embryos turn into larvae. Larvae are much more mobile than embryos. Silver carp grows quite quickly. By the end of the first year it reaches 12 - 13 centimeters, in the second - 25 - 26 centimeters, and in the sixth year more than 50.
Silver carp lives in schools.
When knocking, fishing, or shadows appear, it jumps out of the water, sometimes to the height of a man. If a school of silver carp swims by and a boat appears at this place, they jump out of the water, getting into the boat. Sometimes so many of them fall into the boat that it can sink. This must be kept in mind when catching silver carp: the upper catch of the seine should be raised high above the water, otherwise the fish may jump out of the seine.
Silver carp meat is of high taste, but soon spoils.
Silver carp easily acclimatizes even in areas very far from its habitat. It should be added that silver carp is also resistant to a serious, dangerous disease that affects many cyprinids - rubella.
Nowadays, silver carp lives among the local fish of the Azov Sea estuaries. The first attempts to acclimatize this fish were made in the 1930s.
Silver carp grows well together with other fish (carp, tench, sterlet, silver carp, etc.).
Breeding silver carp and relocating it to new places is of great economic interest.
He was also relocated to the Caspian Sea, where he will enrich the composition of the local fish “population”, which is relatively poor in terms of species. Currently, broodstocks of silver carp have been created in several pond farms in Central Asia and the North Caucasus. From here, its larvae are sent by the millions to the country's pond farms.
Silver carp has a lot in common with silver carp: these fish are often talked about together when it comes to their location, acclimatization, and the benefits they bring.
Like silver carp, grass carp is an inhabitant of the waters of the Far East. It was also grown in China more than a thousand years ago. It is found, in addition to the rivers of China, in the Amur and its tributaries, as well as in the lakes adjacent to it.
This is a fish more than a meter long and weighing 50 kilograms or more. Its color is light, its back is yellowish or greenish-gray, its sides are golden. The pharyngeal teeth are serrated, with grooves, and are good at crushing plant foods. Before spawning, males develop numerous white tubercles on their pectoral fins.
Juvenile grass carp feed on small planktonic crustaceans, and adults feed on plant food (elodea, pondweed, sedge, chilim), not only aquatic, but also terrestrial: it can eat mown grass thrown into the water, cabbage leaves, beet tops, etc.
It, like silver carp, can be used as a reclamation agent for water bodies, eliminating their overgrowth.
Cupid is growing quickly. Reaches sexual maturity at 6 - 7 years. Its spawning occurs at the end of spring in the river bed. The number of eggs laid by one female is 800 thousand or more. Large pelagic caviar.
7 days after hatching from eggs with a length of 8 millimeters, the larvae capture food by swimming near the bottom. At the age of 16 days, the larvae feed on plankton. At the age of 22 days (with a length of 14.7 millimeters), they already feed on plankton and benthos, and also swallow a lot of filamentous algae. Sometimes filamentous algae fill the intestines of the larvae to capacity.
Grass carp are migrating. After absorbing the yolk sac, juvenile grass carp migrate from the river bed to the coastal zone. In autumn, it leaves the coastal zone and winters in holes in the riverbed or channels of the Amur. Before spawning, adults partially enter the lakes. This happens at the end of April. After spawning, the spawners go to floodplain lakes and are distributed among the floods, where they feed intensively.
Cupid lives without gathering in large flocks.
Like silver carp, grass carp grows well in ponds when reared together with other fish. Such cultivation is advisable because it does not compete with other fish for food.
It also requires little oxygen. In addition, like silver carp, it is resistant to rubella.
White carp is one of the valuable and interesting fish, breeding which in ponds promises great benefits.
For more than 10 years now, Far Eastern river invaders, having changed their “registration”, have been accustomed to the new pond conditions of the Alexandria experimental base of the Institute of Hydrobiology of the Academy of Sciences of the Ukrainian SSR. These fish are now grown in the ponds of the Nivki fish farm near Kyiv, the Donfish Factory in the Donetsk region, as well as in reservoirs in the Kharkov and Odessa regions. This fish is successfully grown in the Moscow region, Krasnodar region, Turkmenistan, Uzbekistan and other regions of the USSR.
Significant results were achieved by the use of reclamation fish in the ponds of the thermal power plant named after. Klasson (Moscow region). The cooling ponds are no longer overgrown.
In 1956, in the ponds of the Alexandria experimental base, 58 quintals of fish per hectare were obtained in polyculture. The following animals were grown in the pond: carp, silver crucian carp, carp-crucian carp hybrids, Azov bream, sterlet, grass carp. The fish were fed with a feed mixture of barley, corn, oats, lupine, cakes (soybean and rapeseed), pine flour, and silkworm pupae.
As a result, four-year-old grass carp gained 604 grams, and five-year-olds - 1200 grams.
In 1963, eight-year-old grass carp in polyculture produced an increase of 1100 grams. Thus, growing Amur fish, in particular grass carp, in polyculture in pond conditions is very promising: it makes it possible to increase the natural fish productivity of carp ponds by 150 - 200 percent or more due to more complete use of their food supply.
It should be noted that the cupid has an enviable appetite: in a day it eats almost as much food, that is, aquatic plants, as it weighs. Therefore, the results of his activities are felt after a short time.
For successful acclimatization of Amur fish, it is necessary to continue studying their biological characteristics (lifestyle, nutrition, spawning conditions). Finding out and understanding the secrets of spawning is very important. The spawning of grass carp and silver carp differs from the spawning of many fish in our reservoirs, since it takes place under conditions of extremely weak spring and powerful summer floods, that is, with a sharp change in the water level in the Amur, which is located in the monsoon climate zone. Severe summer floods there are caused by the beginning of the rainy season, and there are several such floods during the summer. This must be kept in mind when organizing the spawning of grass carp and silver carp in our reservoirs.
A little time will pass, and in lakes and rivers our fishermen will diligently use clover, willow, beet or even sedge leaves for bait instead of worms. The fish productivity of ponds in which herbivorous fish will be raised will double. Extensive work on the acclimatization of these fish continues. In a number of pond farms, grass carp offspring are obtained and the larvae are sent to all parts of our country and to foreign fish farms.
Therefore, mature individuals have significant weight, which attracts fish farmers. In addition, white is specially diluted in and -coolers of power plants, since it cleanses them of unnecessary vegetation. This fish eats not only aquatic vegetation, but also vegetation on river banks, and does not disdain vegetable peelings, cabbage leaves, and potato skins. Cupid is even capable of jumping out of the water to grab a branch of a plant he likes with his teeth. Together with the increase in their own weight, cupid and silver carp improve the hydrological regime of rivers and lakes. In addition, these fish are resistant to infectious diseases and are undemanding in terms of keeping conditions. The herbivorous fish overwinters at the bottom of pits. At a water temperature of +10 degrees C, phytophages stop feeding, and at a temperature of +5 degrees C they switch off altogether and stop responding even to external stimuli. The only danger of breeding phytophages in reservoirs is that they are capable of destroying all vegetation in a pond or lake and disturbing thereby ecological balance. Artificial breeding of phytophagous fish has become popular and profitable for some time now. They are bred in ponds along with carp, with juveniles of carp and silver carp added there. There are also phytophagous aquarium fish. These are everyone's favorite goldfish, large cichlid fish. They also feed on plants, so you need to be careful when introducing them into the aquarium. In addition, some species of cichlid fish feed on fouling from stones and require special alkalized water, which is unacceptable for other fish. Some fish, catfish, are specially added to the aquarium to clean it. But other types of phytophages, the beautiful Abramites, for example, are capable of destroying the entire flora of an aquarium in a few minutes.
Video on the topic
Tip 2: Why are mainly herbivorous fish bred?
Herbivorous fish, or phytophages (from the words “phyto” - plant and “phage” - eater), can be found in any body of water on our planet, with the possible exception of Lake Baikal. Representatives of this group are also bred in home aquariums. What is their popularity?
Fish are usually divided into several groups: carnivores (carnivores) and omnivores. Based on this, herbivores include fish that feed on various parts of aquatic plants.
To understand that in fish farming, preference is given to the breeding of herbivorous fish, let us arrange all the inhabitants of the reservoir according to the nature of their diet. The result is a food chain, each link of which is food for the next. The food chain of a reservoir looks like this: plants - invertebrates - fish. It is phytophages that are the final product of the shortest food chain of any body of water: algae - fish.
For comparison, the food chain for fish looks like this: algae - invertebrates - benthos (organisms that live on the bottom or in the soil) - small fish - predatory fish. If we take into account that with an extended food chain, the energy costs for obtaining the final product (fish) increase many times over, then it becomes clear that breeding herbivorous fish is energetically more profitable. In addition, phytophages grow much faster than carnivores, which means they are more actively used for breeding.
Unlike industrial fish farming, there is no doubt about the interest in breeding herbivorous fish for aquariums and ornamental ponds. This is their attractive appearance. But in the case of ornamental fish, their love for plants is rather a disadvantage. After all, when designing an aquarium or pond, it should be taken into account that these fish consider any plant as a source of food. In addition, herbivorous fish eat little but often. They need food after 2-3 hours, and by morning they are very hungry.
Sources:
- herbivorous fish in 2018
Herbivorous fish.
In the CIS, as in many other countries of the world, Far Eastern herbivorous fish belonging to the carp family are used in pond fish farming:
Common, or white, silver carp Hypophthalmichtys molitrix (Val.) (Fig. 42, a). This is a large schooling pelagic freshwater fish, the length of which reaches 1 m, weight -16 kg. Natural distribution area (area) - rivers of East Asia; in Russia - Amur. Acclimatized in some southern rivers of the CIS. The body is tall, covered with small silvery scales. The head is wide, the eyes are below the midline of the body. The fused gill rakers form a filter. The ventral surface has a keel starting from the throat; the intestine is 10 or more times longer than the body. In the Amur it reaches sexual maturity in the 5th-6th year, spawning occurs during the summer flood at a water temperature above 20°C; bighead carp Aristichthys nobilis (Rich.) - close to white, but more heat-loving, from the rivers of Central and Southern China, distinguished by a darker body color and the absence of a keel on the throat (see Fig. 42, b);
grass carp Ctenopharyngodon idella (Val.) is a large freshwater fish that inhabits the same reservoirs as silver carp. It matures in the 7-8th year of life with a length of 65-70 cm. The body is low, elongated, covered with large scales, reaching a length of 122 cm and a weight of 32 kg.
All herbivorous fish are fast-growing, but more thermophilic than carp. Therefore, they are most effective in polyculture of reservoirs in the southern fish farming zones.
Grass carp feeds on higher aquatic vegetation. It is capable of very quickly destroying its own food supply (especially in the southern regions). If there is a lack of vegetation, it easily switches to feeding on compound feed, which can lead to competition with carp. When reared together, grass carp have the same growth rate as bighead carp. It is advisable to use it in pond farming as a biological ameliorator.
Silver carp feeds on microscopic algae - phytoplankton, as well as detritus. There is practically no competition in nutrition with carp and other species in polyculture. When silver carp and carp are reared together, their mutual positive influence on each other can be observed.
Bighead carp is conventionally called a herbivorous fish. Along with zooplankton and detritus, it consumes phytoplankton. With a significant increase in stocking density, it can compete with carp fingerlings in feeding on zooplankton. In the middle zone it grows better than silver carp. In the southern regions of the CIS countries, with a good supply of food, carp grows faster. Herbivorous fish can be grown in lakes, reservoirs and other non-drainage bodies of water (Table 69). For organizing feeding farms on the basis of reservoirs, the most promising are silver carp and its hybrids with bighead carp.
Table 69. Average productivity values of herbivorous fish in various fish-breeding areas of the CIS countries, c/ha
Growing producers. The North Caucasus, southern Ukraine, Moldova, the states of Transcaucasia and Central Asia are most favorable for growing producers of herbivorous fish. In the middle zone, it is advisable to use the warm waters of state district power plants.
Breeders of carp and silver carp can be raised in specialized zonal farms at reproductive complexes. Fish breeding material can be grown in ordinary carp ponds. Joint rearing of fish of the same species, but of different ages, is not recommended [Vinogradov, Erokhina, 1976].
Repair and producers of white and bighead carp can be grown together with carp breeding material. The standards for planting carp in this case apply the same as when growing it in a monoculture. Grass carp can be grown in the same ponds with carp (without feed additives).
In addition to the usual ponds necessary for growing and maintaining breeding material (fry, nursery, feeding, wintering, uterine, quarantine), the reproductive complex includes:
a workshop for incubating eggs and keeping larvae, which is equipped with VNIIPRH incubation devices with a capacity of 200 liters and IVO-2 devices for keeping larvae. The workshop is supplied with water from a settling pond, which provides water with a temperature of more than 18° C during the spawning period. For a successful spawning campaign, it is necessary to have replaceable equipment used for incubating carp and other fish eggs;
earthen cages for keeping breeders after injection, each with an area of 30-50 m2;
ponds for pre-spawning maintenance of spawners with an area of 0.1-0.2 hectares each.
Female silver carp mature in the southern zones, as a rule, at the age of 3-4 years, bighead carp - 4-5, grass carp - 4 years (Table 70). Males reach sexual maturity much earlier than females. When creating replacement-tagging herds, the use of females maturing for the first time, as well as sires older than 10-12 years, should be avoided.
The requirements for the basic parameters of the hydrochemical regime of ponds when growing herbivorous fish are the same as when growing carp.
In ponds where repairs are grown and spawners are kept, it is necessary to create a sustainable food supply.
Table 70. Working fertility of female herbivorous fish (numerator - absolute, thousand pieces per female; denominator - relative, thousand pieces/kg)
| Age, years | Silver carp | Bighead carp | White amur |
| 3 | 167/83,5 | - | - |
| 4 | 332/107 | 293/52,9 | 302/63 |
| 5 | 486/105,6 | 620/73 | 434/81,9 |
| 6 | 488/108,4 | 780/70,3 | 560/85 |
| 7 | 805/146,4 | 730/70,2 | 561/76,7 |
| 8 | 546/85,4 | 605/46,1 | 911/95,5 |
| 9 | 631/101,2 | 850/56,6 | 834/72,5 |
| 10 | 566/77,6 | 900/50,3 | 646/61 |
| 11 | 744/106.3 | 796/67,4 | 916/91,6 |
| 12 | 1000/133 | 840/68,3 | 740/75,4 |
| 13 | 912/84,4 | 1244/65,1 | 700/70 |
| 14 | 786/68,3 | 903/45,8 | 720/66,7 |
| 15 | 103/90 | 1000/48,5 | 775/63 |
During periods when there is a lack of aquatic vegetation in ponds, grass carp (especially older age groups) should be fed with terrestrial vegetation (alfalfa, clover, corn, forbs, etc.), their feed coefficient is taken to be 30.
During autumn fishing and when transferring fish for wintering, the number of fish is taken into account, the piece weight and growth are determined, and sick, deformed and injured individuals are discarded. Wintering is carried out in ordinary carp wintering ponds. Ponds of other categories can also be used, where favorable conditions can be provided. The density of planting of breeding herbivorous fish in wintering ponds is as follows: for fingerlings - up to 200-300 thousand fish/ha; for two-year-olds - 200 c/ha; for older breeding material -150 c/ha, for producers -100 c/ha.
If carp are bred on a farm along with herbivorous fish, it is more convenient to winter them separately or with a predominance of herbivorous fish in the planting. The yield standards for various age groups of herbivorous fish during the wintering period are the same as for carp. Wintering ponds are designed to keep breeders separate.
When feeding grass carp with terrestrial vegetation, its production can be increased by 2-3 c/ha.
Standards for growing repairs and producers of herbivorous fish
| Ratio of sires, females: males | 2:1 |
| Manufacturers reserve, % | 100 |
| Average duration of use of manufacturers, years | 4 |
| Working fertility of females, thousand pieces. eggs | 500 |
| Number of larvae per female, thousand pieces. | 250 |
| Density of stocking of spawners in pre-spawning ponds, pcs./ha | 1000 |
| Age of producers first used for reproduction, years | |
| females | 6-5 |
| males | 5-4 |
| Survival rate in maintenance ponds, % | |
| fingerlings from larvae | 40 |
| fingerlings from grown up to 25 mg larvae | 75 |
| yearlings | 85 |
| two-year-olds | 85 |
| two-year-olds | 90 |
| three year olds | 90 |
| three-year-olds and older age groups | 95 |
| Repair selection, % | |
| yearlings | 50 |
| two-year-olds | 50 |
| two and three year olds | 95 |
| three- and four-year-old females and males | 95 |
| four year olds | |
| females | 95 |
| males | 37-95 |
| five-year-old females and males | 95 |
| five year olds | |
| females | 75-95 |
| males | 37 |
| six year old females | 95 |
| six year old females | 75 |
| Average weight of fingerlings taken for repair, g | |
| grass carp | 80 |
| bighead carp | 80 |
| silver carp | 40 |
| two-year-olds, kg | |
| grass carp | 1,35 |
| bighead carp | 1,35 |
| silver carp | 0,85 |
| three-year-olds, kg | |
| grass carp | 3 |
| bighead carp | 3 |
| silver carp | 2 |
| four-year-olds, kg | |
| grass carp | 5 |
| bighead carp | 5 |
| silver carp | 3 |
| five-year plan.kg | |
| grass carp | 7 |
| bighead carp | 7 |
| silver carp | 4 |
| six-year-olds.kg | |
| grass carp | 9 |
| bighead carp | 9 |
| silver carp | 5 |
| Density of stocking of replacement stock in summer repair ponds in a polyculture with carp, pcs/ha | |
| larvae | |
| grass carp | 3000 |
| bighead carp | 9500 |
| silver carp | 25500 |
| larvae grown up to 25 mg | |
| grass carp | 1700 |
| bighead carp | 5000 |
| silver carp | 13500 |
| yearlings | |
| grass carp | 90 |
| bighead carp | 190 |
| silver carp | 140 |
| two-year-olds | |
| grass carp | 70 |
| bighead carp | 100 |
| silver carp | 250 |
| three-year-olds | |
| grass carp | 50 |
| bighead carp | 70 |
| silver carp | 190 |
| four-year students | |
| grass carp | 50 |
| bighead carp | 50 |
| silver carp | 180 |
| five year olds | |
| grass carp | 50 |
| bighead carp | 50 |
| silver carp | 170 |
| Planting density of breeders in summer brood ponds in polyculture with carp, pcs/ha | |
| White amur | |
| females | 10 |
| males | 10 |
| bighead carp | |
| females | 30 |
| males | 50 |
| silver carp | |
| females | 80 |
| males | 120 |
| Increase in producers in summer brood ponds, kg/piece | |
| White amur | |
| females | 1,5 |
| males | 1 |
| bighead carp | |
| females | 1,5 |
| males | 1 |
| silver carp | |
| females | 1,3 |
| males | 0,8 |
| Planting Density | |
| fingerlings in winter maintenance ponds, thousand pcs/ha | 200-300 |
| producers in winter ponds for all age groups, pcs/ha | 1000 |
| replacement stock in winter ponds for all age groups, except fingerlings, t/ha | 10-20 |
When forming broodstocks of herbivorous fish, it is necessary to use the two-line breeding recommended for carp - the reproduction of two unrelated groups of fish with the selection of females and males of different origins. This allows you to avoid inbreeding and expect rapid growth of hybrids.
The main selection for the broodstock is carried out among first-time maturing sires based on the degree of expression of sexual characteristics. Under favorable housing conditions, at least 80-90% of females and almost all males are selected from the older age group of repairs as spawners.
When determining the size of a farm's broodstock, it is necessary to take into account that, for a number of reasons, some females do not mature after injection or produce eggs that are not entirely of good quality. Therefore, it is necessary to have a reserve of females in the broodstock (at least 50%). There is no need to have a reserve of males, since when producing the offspring of herbivorous fish, artificial insemination of eggs is carried out; fewer males are required than females. For every 5 female silver carp in the broodstock, it is enough to have 3-4 males, and for every 5 female grass carp - 2-3 males.
When grading breeding material of herbivorous fish, the same techniques can be used as when grading breeders and repairing carp. Every year in the spring, when the wintering ponds are unloaded, all fish are inspected, weighed, and the necessary measurements are taken.
Fish from wintering areas are caught by water using a Hamsoros seine. Fish are selected from the seine using fabric sleeves 1-1.3 m long, placed on one side on a metal hoop with a diameter of 30-35 cm. The caught spawners are transferred to stretchers with water, equipped with canvas covers. The length of the stretcher is 1.5 m, the width is 40-45 cm. For weighing, deep stretchers (cradles) are used. Producers are kept in wintering ponds until spawning begins. Carrying out grading of broodstock at an earlier stage is pointless, since before the onset of spawning temperature, producers often do not have well-defined sex differences.
The main sign indicating the readiness of females for spawning is the presence of a convex, pendulous abdomen. This sign is especially clearly expressed in white and bighead carp, and to a lesser extent in grass carp.
A characteristic feature that allows one to distinguish males of herbivorous fish from females (in addition to the secretion of milk) is the presence of peculiar horny denticles - spines - on the rays of the males on the inner side of the pectoral fins. They are most clearly visible in male silver carp - large and sharp (usually on the second and third rays). In bighead carp they are less sharp, in the form of tubercles. Male grass carp have very small spines (most pronounced on the first hard ray), and the upper surface of the pectoral fins feels like sandpaper to the touch.
Spines on the pectoral fins of male silver carp can be found throughout the year. Male grass carp have spines on their pectoral fins only during the feeding period; in the fall, when the temperature drops, they disappear and appear in the spring, after the water warms up. Some female silver carp (especially older ones) also have teeth on their pectoral fins, but they are located much less frequently.
During grading, females are divided into 3 groups:
1. The most mature females. The abdomen is soft to the touch, saggy. Sometimes swelling is noticeable in the area of the genital opening. This group of females is used primarily for work.
2. Females with similar external characteristics, but less pronounced. They can be used later, after finishing work with females of the 1st group.
3. Females are almost no different in appearance from males. They are not used to obtain caviar, but are immediately discarded after grading or planted for summer feeding.
During grading, males are divided into 2 groups:
1. Males give milk easily and have a well-defined nuptial plumage.
2. Males produce very little milk or do not flow. Fish selected for offspring by species, sex and groups are placed in ponds for pre-spawning maintenance. Producers are kept in them until reproductive products are obtained.
For pre-spawning housing, spawners use small, easily fished ponds with an area of 0.05-0.2 hectares and a depth of 1.5-2 m. Ponds for pre-spawning housing should be well planned, quickly drained and filled with water (no more than 2-3 hours) , have a constant water exchange to prevent excessive heating of the water. A good oxygen regime is a prerequisite: a drop in oxygen content below 4 mg/l in pre-spawning ponds is unacceptable. Planting producers in ponds up to 1000 pcs/ha, but not more than 10-15 c/ha. Overexposure of mature females in ponds with spawning temperatures leads to the appearance of degenerative changes in the ovaries, that is, to overripeness of the females. Males mature 10-15 days earlier.
During industrial breeding of herbivorous fish, significant post-spawning mortality of spawners, especially silver carp, is observed. It is not uncommon for more than half of the producers to die.
The main reasons causing the death of spawners during the spawning campaign:
1) injuries during fishing, injection and straining of caviar and milt;
2) the use of females that do not respond to pituitary injections to produce offspring.
Incomplete ovulation may be a consequence of an underestimated dosage of the pituitary gland, but there is never a deterioration in the condition of the fish after the first (preliminary) injection. Careful spring grading and carrying out work to obtain offspring of herbivorous fish in a short time make it possible to avoid the use of females that do not mature after pituitary injections and to significantly reduce the death of spawners during the spawning campaign.
To prevent injuries, practice-proven methods are used:
the use of earthen spawning cages with hidden hydraulic structures;
catching fish using special hoses;
use of anesthesia.
Post-injection inflammatory processes in producers of herbivorous fish are relieved with penicillin. Producers weighing from 5 to 12 kg are administered 50 thousand IU per fish.
In Turkmenistan and Uzbekistan, work begins approximately in early May, in the Krasnodar Territory - in the second half of May, in Moldova - in early June, and in the Astrakhan, Volgograd and Rostov regions - in the northernmost disengagement points - in the second half of June.
Prolonged maintenance of spawners at spawning temperatures leads to their overripeness, therefore all work on the reproduction of herbivorous fish should be carried out in a short time - 25-30 days. As a rule, silver carp and grass carp are the first to ripen. After a few days (7-10), depending on the water temperature, they begin working with bighead carp.
The method of factory reproduction of herbivorous fish has almost no significant differences for individual species.
Females with gonads in stage IV of maturity are given a preliminary pituitary injection at the rate of: for each, 3 mg of pituitary dry matter with a weight of 5-7 kg and 5-6 mg for larger ones. A day after the preliminary injection, a permissive injection is made at the rate of 3-6 mg of pituitary dry matter per 1 kg of female weight, depending on the size of the gonads. At the same time, males weighing 5-7 kg are administered 4-6 mg, larger ones - up to 10-12 mg of pituitary dry matter per fish.
Currently, choriogonic gonadotropin and synthetic gonadal otropic hormones are also used to stimulate the maturation of herbivorous fish.
The injection time of the producers is chosen in such a way that, taking into account the water temperature and the rate of maturation of the females, the receipt and insemination of eggs, and their placement in the incubation apparatus, occur during daylight hours. A preliminary injection is carried out, as a rule, at 18-19 hours, allowing - starting from this time and later. However, during sudden cold spells at night, injections are sometimes postponed to the morning. If the average daily water temperature drops below 20° C, work is stopped until warming occurs.
After injection, males and females are planted separately in small injection cages with an area of 20-30 m2, equipped with a bottom drainage through a grate and a canvas sleeve on the water supply pipe. Ponds must have constant water exchange; water must be released from them and the cages filled in no more than 30 minutes. Up to 10 breeders are planted in each cage. It is possible to keep the breeders in container baths made of tarpaulin, fiberglass and other materials, while ensuring constant water exchange. The water consumption is 3-4 l/min. During the entire period of reproduction work, water in cages and containers is carefully monitored.
The rate of maturation of females after a permissive injection largely depends on the water temperature
| t water/С | 20-22, | 23-25, | 26-28 |
| Ripening time, h | 10-12, | 9-11, | 7-10 |
After 6-9 hours, they begin to regularly check the state of maturity of females. The interval between checks is determined depending on changes in water temperature during the day, age and condition of the females. But it cannot be more than 1.5-2 hours. This is due to the danger of overripening. For ease of work, it is advisable to sort females of different sizes, origins and degrees of maturity into groups. If the females are heterogeneous, it is necessary to transplant them upon inspection into a free, water-filled cage or container. In this case, all females are examined, since they can mature at different times. Determining the exact time of ripening is very important, but this can only be done professionally by a specialist with extensive practical experience in working on fish farms.
Milt is collected in separate test tubes for each male 30-60 minutes before the start of work on obtaining caviar. You can not store milk, but express it directly onto the caviar. It is important to wipe the male's abdomen well so that no water gets into the milk; Store milk in a thermos on ice for 6-12 hours.
The amount of caviar is taken into account by weighing a previously prepared basin with caviar, determining the volume of caviar directly in the basin using calibrated marks or by pouring it into a measuring container, preferably into a nylon or polyethylene mug with divisions. You can express caviar into such a mug when selecting it from a female. 1 g or 1 ml of unfertilized eggs of herbivorous fish contains 800-1000 eggs of grass carp, 900-1200 of white carp and 600-800 of bighead carp.
The fertility of female herbivorous fish varies widely - from several tens of thousands to 2 million. But for fish farming calculations, the working fertility of a repeated spawning female weighing 5-7 kg is taken on average equal to 500 thousand eggs.
Immediately after determining the number of eggs, they are inseminated with sperm from 2-4 males. For 1 liter of caviar, 5 ml of sperm is enough. The milk is carefully spread over the caviar using a bird's feather, a small amount of water is added and the caviar is carefully distributed in it. At this time, fertilization occurs. After 1-2 minutes, add fresh water and drain it, repeating this operation 1-2 more times. You can wash the caviar from mucus, blood, scales, and lumps of caviar for several minutes; placing a hose with low-flowing water on the edge of the basin to prevent the eggs from being carried away. Without waiting for complete swelling, no later than 5-10 minutes after fertilization, the eggs are placed in incubation apparatus.
It is advisable to place the eggs of each female for incubation in a separate apparatus. It swells a lot. The diameter of the unfertilized egg is 1.0-1.2 mm, and after swelling - 5 mm or more.
A standard Weiss incubator with a volume of 8 liters holds only about 50 thousand eggs, so the use of these devices for incubating herbivorous fish is ineffective, given their high fertility. Therefore, devices made from plexiglass of the VNIIPRKh system with a capacity of 50 to 200 liters are used (Table 71).
Table 71. Basic technical data of incubation apparatus for herbivorous fish
When feeding water with high mineralization (1.6-2.0 g/l) into the apparatus, the amount of eggs laid can be increased by 2-2.5 times due to its less swelling.
Before laying the eggs, the water level in the apparatus is reduced by one third, adjusting its supply so that the eggs are in slight movement in the lower part of the apparatus, and the water consumption, after the eggs swell, does not exceed the required value. Water is supplied to the incubation workshop from the settling pond through a filter made of a thick nylon sieve (no. 46 and above). If heating is used, water is supplied to the workshop through a pool, where air bubbles are removed, which can, by attaching to the eggs, carry them out of the apparatus with a current of water.
During incubation, eggs are also released; increasing at water temperatures below 17°C, it is accompanied by an increase in the number of deformities. The quality of eggs and the results of incubation are greatly influenced by the conditions of keeping the spawners during the feeding period and pre-spawning time.
Before the end of incubation, the percentage of malformed embryos and the percentage of free embryos are determined. These indicators can be used when selling larvae to determine their number in each apparatus. Under favorable incubation conditions and good quality reproductive products, the yield of free embryos is at least 70-80% of the amount of laid eggs. If during aging there is a significant loss of larvae, their number is determined again by the standard method.
During the incubation period, water exchange in the apparatus is maintained in such a way that the eggs are not washed out and at the same time, stagnant zones do not form. If there are a large number of dead eggs, they are selected after the end of the gastrulation process, that is, 13 hours after the start of incubation, by suction with a rubber hose, while slowing down the water exchange in the apparatus by half. The duration of incubation depends on the temperature of the water entering the apparatus. At an optimal temperature in the range of 21-25°C, it is 23-33 hours, decreasing to 17-19 hours when the water temperature rises to 27-29°C. This dependence applies to all types of herbivorous fish. Mass hatching of embryos occurs within 1-3 hours, sometimes it lasts up to 12 hours, and sometimes for a day. In these cases, the hatching process is artificially stimulated by reducing the water supply by 3-5 times for several minutes, restoring the flow after hatching occurs in order to avoid freezing.
Soon after hatching, free embryos rise to the upper layers of the water and, together with the current, are carried out of the apparatus through gutters or hoses into the holding apparatus.
Most often, IVA-2 devices are used for keeping larvae.
The rearing of larvae of herbivorous fish in fry ponds is carried out in stages (Table 72).
Table 72. Technological operations for growing larvae of herbivorous fish in fry ponds
| Name | Description | lead time |
| Reclamation works | Clearing and deepening the drainage network, removing dry vegetation, liming | - |
| Application of organic fertilizers | Adding humus or compost to the pond bed (3-5 t/ha) | 30 days before pond filling |
| Filling the pond with water | Water supply through a fish catcher from a nylon sieve N 32 installed on the water supply pipe | In 1-2 days, planting the larvae |
| Cleaning the fish catcher | Removing the contents of the catcher | Before draining the pond |
| Planting larvae | Release of larvae into ponds at the stage of mixed feeding after preliminary counting (visually using a standard or volumetric method); before releasing the larvae, the temperature of the water in the transport containers where they are transported is equalized with the temperature of the water in the ponds | - |
| Application of mineral fertilizers | Application of mineral fertilizers by water at a one-time rate of 30 kg/ha of ammonium nitrate and 15 kg/ha of superphosphate, the total fertilizer consumption is 1.0-1.5 c/ha for the entire period | Weekly |
| The use of organic fertilizers with poor development of the natural food supply and favorable oxygen conditions in ponds | Application of humus, compost (2-5 c/ha) along the water edge or dried vegetation in the form of sheaves along the coastline (5-10 c/ha) | On the 3-5th day after planting the larvae |
| Control of predatory aquatic insects | Introduction of high-molecular alcohols into the pond at a single rate of 300-500 g, the total consumption of higher fatty alcohols, depending on wind strength, is -15 kg/ha for the entire period | Every day from the moment the ponds are filled with water until the end of the 3rd growing period |
| Temperature observations | Measuring water temperature using a water thermometer | Three times a day |
| Observations of the gas regime | Determination of oxygen dissolved in water using an oximeter or the Winkler method | Every day, at 6 and 16 o'clock |
| Observations on the development of natural food resources | Sampling of zooplankton using a plankton grid, qualitative and quantitative sample processing, algae development is determined using a Secchi disk, optimal development corresponds to a water transparency of 35-40 cm | Daily |
| Observations on the growth rate and nutrition of juveniles | Carrying out control catches, selecting 30 specimens. for weighing, measuring and studying nutrition | Once every 10 days of juveniles, |
| Installation of a fish catcher | The fry catcher is installed in a waterproof box using guy ropes and attached to the drainage pipe using a cuff. | Before catching fry |
| Descent of ponds | Removing the sand bars, establishing the difference in water horizons in the pond and in the fry catcher is no more than 10 cm | During the period of draining water from ponds |
| Installing a screen in the "monk" and catching juveniles from the catcher | The grown juveniles from the catcher are caught in leaps and bounds and transferred to a bucket of water, and then to a cage installed on running water. | In the early morning hours and evening |
| Keeping juveniles in cages before transportation | Keeping in running water | Within 4-6 hours |
| Counting and transporting juveniles | Counting of juveniles is carried out visually: according to a standard or by volumetric method; transportation within the farm is carried out in milk cans, plastic bags and live fish machines | The duration of on-farm transportation should not exceed 1 hour |
Work on raising larvae of herbivorous fish is carried out at water temperatures above 20° C (preferably 23-28° C). Short-term drops in water temperature during the growing period to 16-18°C are acceptable. The optimal content of oxygen dissolved in water is 6-12 mg/l; it is permissible to reduce the oxygen content to 4-5 mg/l.
Technical standards for equipment for raising fry of herbivorous fish
| Fry Pond | |
| area, ha | up to 1 |
| average depth, m | 1,0-1,5 |
| duration, h | |
| filling the pond | 12 |
| draining the pond | 24 |
| Tray fish catcher | |
| metal mesh mesh, mm | 0,5 |
| nylon sieve | ╧ 32 |
| Sleeve made of nylon sieve | |
| length, m | 2,5-3 |
| diameter, cm | 50 |
| nylon sieve | ╧ 32 |
| Fry catcher (wooden box or concrete pool), m | |
| length | 3,5-4 |
| width | 1,2-1,5 |
| height | 0,8-1 |
| water layer height | 0,6-0,8 |
| difference in water horizon in a pond and in a filled box, cm | no more than 10 |
| Catcher made of nylon sieve, cm | |
| length is less than the length of the box or pool | by 50 |
| width is less than the width of the box or basin | no more than 15-20 |
| Anti-chip partition (sewn into 1/3 of the catcher’s width) | |
| length shorter than catcher length, cm | at 15-20 |
| material - nylon sieve | ╧ 7-12 |
| Cage for keeping grown juveniles before transportation | |
| material - nylon sieve | ╧ 7-12 |
| wooden frame, m | |
| length | 1 |
| width | 1 |
| height | 0,45 |
| distance from the bottom of the cage to the bottom of the reservoir, m | not less than 0.4 |
| water flow speed in the area where cages are installed, m/s | 0,05-0,2 |
| Net for catching juveniles | |
| diameter, cm | 30 |
| depth, cm | 30 |
| material - nylon sieve | ╧20-23 |
Biological standards for rearing and transporting juveniles
| Planting density of herbivorous fish larvae obtained in a factory way, million pcs/ha | 1,5-5 |
| Average weight of fry at the end of growing, mg | 20-30 |
| Survival rate of juveniles in fry ponds, % | 40-50 |
| Duration of growing, days | 10-15 |
| Optimal concentration of zooplankton | |
| in fry ponds, specimens/l | 1000-1500 |
| Phytoplankton biomass, mg/l | no more than 30 |
| Permissible concentration of grown juveniles in cages, thousand pieces/cage | no more than 70 |
| Duration of keeping juveniles in cages before transportation, hours | 4-6 |
| Norm for placing juveniles in plastic bags or milk cans with a capacity of 40 liters without oxygen (thousand pieces) for transportation duration, hours | |
| up to 4 | 2 |
| up to 8 | 1 |
| Norms for placing juveniles in live-fishing machines (tank capacity 3 m3) without aeration for a transportation duration of up to 8 hours, thousand pcs. | 100 |
| Norm for placing juveniles in plastic bags with a capacity of 40 liters with oxygen (thousand pieces) during long-term transportation with weight, mg | |
| 5-30 17-25 | |
| 30-50 | 10-15 |
| Norm for placing juveniles in live-fishing machines (tank capacity 3 m3) with aeration (thousands of pieces) during long-term transportation with a weight of 10-20 mg | 18-20 |
The duration of the larval incubation process depends mainly on the water temperature:
The survival rate (from fertilized eggs to larvae switching to mixed nutrition) should be at least 50%.
For incubation of eggs and maintenance of free embryos of herbivorous fish, universal incubation devices ("Amur", etc.) are used, which makes it possible to simplify the entire technology for producing larvae.
In China, Japan and India, flow-through round and rectangular pools are also used to obtain the caviar of herbivorous fish.
The sum of active temperatures (above 15°C), ensuring the normal functioning of the reproductive system of herbivorous fish, must be above 2600 degree days. The supply of heated water to the ponds increases the duration of the growing period and allows, with the targeted formation of the food supply, to obtain standard fish growth, ensuring the possibility of reproduction in the optimal time frame (end of May - first half of June). Artesian wells can be used to regulate the temperature of the water entering the hatchery. Successful temperature management in ponds is limited to an area of up to 1.5 hectares. In ponds of a larger area, the effect of supplying warm water is sharply reduced. The best shape for ponds is rectangular with a length to width ratio of 2:1 or 3:1. The number of days with a water temperature of 20° C and above must be at least 60. This determines the mode of supply of warm water throughout the year (Table 73).
Table 73. Approximate graph of water consumption in ponds of different categories during the year, l/s/ha
| Pond category | Pond area.ha | Spring | Summer | Autumn | Winter | ||||||||
| III | IV | V | VI | VII | VIII | IX | X | XI | XII | I | II | ||
| Pre-spawning | 0,05-0,1 | - | 30 | 40-50 | up to 30 | - | - | - | - | - | - | - | - |
| Summer repair | 1-1,5 | 5 | 25 | 20 | 8-12 | 5 | 5 | up to 20 | up to 30 | 5 | 2 | 2 | 2 |
| Summer-uterine | 0,5-1 | 8-10 | 30 | - | 8-12 | 5 | 5 | up to 20 | up to 30 | 5 | 2 | 2 | 2 |
The mode of supply of warm water to the ponds is adjusted depending on the temperature of the water in the water supply source and weather conditions.
In female herbivorous fish reared in temperature-controlled ponds, the time to reach puberty is significantly reduced due to a reduction in the duration of stages I and II of ovarian maturity. Females of silver carp and grass carp mature at the age of 4 years, bighead carp - at the 5-6th year of life. Males of all species mature a year earlier.
The normative increase in body weight, starting from the third year of life, should be: at least 0.7-0.8 kg - for silver carp and grass carp; 1 kg - for bighead carp (Table 74).
Table 74. Basic standards for growing breeding material of herbivorous fish in ponds with controlled temperatures
| Age, years | Survival rate, % | Silver carp | Bighead carp | White amur | |||
| average weight of fish, g | fish productivity, c/ha | average weight of fish, g | fish productivity, c/ha | average weight of fish, g | fish productivity, c/ha | ||
| Fingerlings | 60 | 30(40) | 3 | 60(80) | 3 | 50(60) | 1 |
| Two year olds | 85 | 400(500) | 1,5 | 800(1000) | 2 | 500(600) | 1 |
| Three year olds | 100 | 1200 | 1,2 | 2000 | 2 | 1400 | 0,8 |
| Four year olds | 100 | 2000 | 1 | 3500 | 1,5 | 2200 | 0,8 |
| Five-Year Plans | 100 | 2700 | 1 | 5000 | 1,5 | 3000 | 0,8 |
| Six-year-olds | - | - | - | 6500 | 1,5 | - | - |
Producers are released for summer feeding at the rate of: silver carp - 60-80, bighead carp - 50-60, grass carp - 40-50 pcs/ha.
Standard indicators of body weight gain for producers during the summer feeding period should be at least 0.8-1.0 for silver carp and grass carp, and 1.0-1.5 kg for bighead carp.
The density of planting of breeding fingerlings of herbivorous fish in wintering ponds is 200-300 thousand/ha, two-year-olds - up to 200, older ones - 150, producers - no more than 100 c/ha. The standards for the release of herbivorous fish from wintering are the same as for carp. Joint wintering of breeders of herbivorous fish and carp due to different breeding periods is not allowed. When forming broodstocks, the needs of farms for planting material of various types of herbivorous fish should be taken into account (Table 75).
Table 75. Productivity indicators of female herbivorous fish
When organizing the artificial reproduction of herbivorous fish under warm-water conditions, the same technological techniques are used as in conventional reproduction complexes.
Growing fingerlings of herbivorous fish. It is carried out together with carp fingerlings. This greatly simplifies the task of creating a sustainable food supply for them.
Small (up to 10 ha), well-planned nursery ponds are used to raise young of the year herbivorous fish. Water supply to these ponds must be carried out through litter traps with a mesh having a mesh of no more than 1 mm.
It is advisable to plant ungrown larvae in ponds soon after filling them with water (no later than 7-10 days). Immediately after delivery to the fish farm, packages with larvae are placed in ponds to equalize the temperature (for about 30 minutes), then the packages are opened, pond water is added to them, after which the larvae are carefully released into the reservoir.
Stocking of nursery ponds with fry raised in fry ponds is carried out using mesh cages measuring 160x75x60 cm, the end walls and bottom are canvas. These cages are installed in pairs in a canvas vat in the back of a car. In one trip, a truck equipped with these cages transports 100-150 thousand. fry depending on ~ their average weight. Under satisfactory growing conditions, the yield from larvae that have switched to a mixed diet and fingerlings should be no lower than 40% in fish farms located in the southern regions of the CIS, and no lower than 30% in fish farms in the middle zone. When stocking nursery ponds with grown juveniles, the yield of fingerlings in the southern zones is planned to be no lower than 70%, in the middle zone - 50%.
When growing herbivorous fish and carp in a polyculture, the natural food supply of ponds is used extremely fully, which makes it possible to significantly increase the productivity of ponds without the additional cost of granulated feed. Forward
Introduction
The development of an organism is a set of quantitative and qualitative changes as a result of the interaction of the organism with the environment. In the individual development of fish, a number of large segments can be distinguished - periods, each of which is characterized by properties common to different species. One of these periods is embryonic, consisting of the moment of fertilization of the egg until the transition of the juveniles to external nutrition. The embryo is nourished by the yolk - a supply of food received from the mother's body.
Herbivorous fish
White cupid (Stenorhagungodonidella)
Fish of the carp family. Length up to 120 cm, weight up to 32 kg. The body is elongated, almost not laterally compressed, covered with dense scales. Along the edge of each scale, except for those located on the belly, there is a dark rim. The beginning of the rounded dorsal fin is located slightly anterior to the base of the ventral fins. The back in front of the dorsal fin and the belly behind the ventral fins are rounded. The pelvic fins do not reach far from the anus; the anal fin is small, slightly rounded. Its back is greenish-gray, its sides are light with a golden tint, and its belly is light golden. The iris of the eyes is golden. The dorsal and caudal fins are dark, all others are light.
White carp is a resident of the Amur (in the middle and lower reaches), Ussuri, Sungari, United Arab Emirates. Khanka, lowland rivers of China. In China, in addition, it is actively bred in ponds; in Russia it is a widely known object of acclimatization.
Grass carp, like other herbivorous fish, are characterized by seasonal migrations over short distances. Its juveniles, after resorption of the yolk sac, move to the coastal zone, where they remain until the end of summer, and in the fall they move to deep places in riverbeds or channels and overwinter in pits separately from adult individuals.
In the reservoirs of the Amur basin, it becomes sexually mature at the age of 7-8 years or more, when it reaches a body length of 70 cm. Before spawning, males develop numerous white tubercles on their pectoral fins. Spawning takes place in the summer, usually when the water level in the river rises during the summer rains. The water at this time is cloudy, saturated with disturbed silt.
Amur spawning grounds are located in sections of rivers with fast flows (1-1.7 m/s, but not more than 3 m/s), usually at the confluence of large tributaries, where sandy and rocky riffles are formed. The speed of the current determines the place of spawning, the time of migration of eggs, larvae and transition to places where there is food corresponding to their age. Spawning in the rivers of China usually occurs once, in the Amur basin - in portions.
Grass carp eggs are large, pelagic, and are spawned in the upper layers of water at a water temperature of 26-30 °C. Egg development occurs as it migrates downstream. At a water temperature of 27-29°C, the incubation period is 32-40 hours. The fertility of grass carp at the age of 7 years reaches 800 thousand, at an older age - 1.5 million eggs.
A week after emergence, the larvae reach a length of 8 mm and are able to capture food by swimming near the bottom. After resorption of the yolk sac, the juveniles select sections of the river with a calm, slow flow, and accumulate in bays, creeks, and oxbow lakes. By three weeks of age, with a length of about 15 mm, the juveniles feed on plankton and benthos, and also eat a lot of algae.
Invertebrates occupy a large place in its diet: chironomids and various crustaceans. When the length is more than 3 cm, the fish switch to feeding on plant foods.
The optimal water temperature at which the greatest feeding activity of juvenile grass carp is observed is 20-22°C; at a temperature of 12°C, feeding activity is reduced by half; at 10°C, the fish stops feeding; at 5°C, it stops responding to external stimuli. The diet of adult grass carp consists almost exclusively of aquatic plants, for which it is also called “grass carp.” The intestines in adults are 2-3 times the length of the body.
The growth rate of grass carp is quite high. During the 1st year, the fish reaches 7-8 cm in length and 15-25 g of weight, in the 2nd year - 15-16 cm and 450-500 g. By the age of 5, grass carp reaches 35 cm and 2.5 kg, by the age of 7 it grows to half a meter or more.
