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.
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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
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.
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 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 maturation is very important, but only a specialist with extensive experience in practical work on fish farms can do this skillfully.
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 of the drainage network, removal of 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 supply | 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 methods 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
Currently, due to the growing influence of anthropogenic factors on the ecosystem of reservoirs, the population size of valuable commercial fish species is catastrophically declining, the reproductive capacity of populations cannot ensure the replenishment of natural reserves in reservoirs, therefore one of the ways to solve this problem is artificial reproduction. Much attention is paid to improving fish farming technology, which in turn will have a positive impact on the numbers of many fish species. Fish farming enterprises are engaged in breeding commercial fish species, obtaining viable juveniles and releasing them into natural reservoirs to feed. These enterprises are located in all fishing reservoirs and basins.
Such valuable commercial fish are herbivorous fish, which are of great importance in the development of the country's fishery industry, as well as environmental significance, which lies in their use as biological (ecological) reclamation agents. This value will increase in the future. The sharp increase in fish productivity provided by herbivorous fish revitalizes the economy. The effectiveness and feasibility of combating water pollution coincides with the interests of the fight for the purity of natural waters. These fish are the most effective means of restoring and stabilizing the biota of water bodies.
Far Eastern herbivorous fish (white and bighead carp, grass carp) have long attracted the attention of fish farmers as highly productive objects, since their value as aquaculture objects lies primarily in their nutritional characteristics. These fish directly use the primary products formed in the reservoir (algae, higher aquatic plants), which makes it possible to obtain marketable products already at the second link of the trophic chain. Across the country, herbivorous fish provide about 25% of the production of pond farms, and in the southern regions 50–70%.
Far Eastern herbivorous fish play an important role in solving the problem of rational use of the natural resources of the country's inland waters. Every year our country produces about
1.5 billion larvae of these fish.
The central issue in solving the problem of increasing the production of seeding material for grass carp and silver carp is the development of scientifically based methods for the formation and operation of broodstock. Currently, the most favorable areas for growing these objects have been identified, the basic techniques of biotechnology have been worked out, the features of development, as well as the influence of environmental factors, have been studied.
The most favorable area for breeding white and bighead carp and grass carp is the Pacific region, in particular the river. Amur, since here are the most suitable conditions for growing them. It is more advisable to use sires of Amur and Chinese origin as starting lines; such organization of breeding allows increasing the survival rate of underyearlings by 15–20%.
When working with herbivorous fish, spawners are obtained by catching them from water bodies. When using such reservoirs, it is necessary to monitor the genetic purity of planting material, as well as monitor the physiological state of the fish. The ability to control the main environmental factors that determine the growth and development of fish, obtaining reproductive products at the optimal time, creates prospects for organizing the reproduction of herbivorous fish.
On the Amur River there are Anyuisky, Bidzhansky, Gursky fish hatcheries, which are run by the Federal State Institution "Amurrybvod", as well as the Luchegorsk fish hatchery station of the TINRO-Center for the production of planting material for herbivorous fish. Their total production capacity is 64 million copies. young Industrial return coefficient in rubles Amur accounted for 1%. A special feature of Amur fish hatcheries is their remoteness from the Amur estuary.
In 1952-1961. catches of herbivorous fish in the river basin. Amur accounted for 37.1-70.8% of total catches, but currently the catches of these fish have decreased significantly and amounted to only 7.1-22.4%.
Employees of the Luchegorsk fish-breeding station of the TINRO-Center felt a surge of interest in breeding grass carp, white and bighead carp several years ago. Then the first commercial farms appeared in the region. The growth of orders for larvae and juveniles of herbivorous fish is increasing every year. Indeed, in the south of the Far Eastern region, only at the fish breeding station of TINRO-Center, broodstocks of Amur carp, German frame carp, colored Japanese carp, white and bighead carp and grass carp have been preserved. This is a typical set of several species and breeds of heat-loving carp fish, which can be successfully grown in lakes, reservoirs, ponds and pools on personal plots, increasing their production to several tens and then hundreds of thousands. In 2008, about 80 organizations and individuals ordered fish seeding material, and applications continue to arrive. This year, several million juvenile and herbivorous fish have already been sold. But the possibilities for growing planting material of different sizes at the Luchegorsk station are limited due to the lack of space for cages.
Therefore, the construction of a fish hatchery in the Amur region is necessary to increase the stocks of herbivorous fish.
The purpose of this course work is to justify the construction of a fish hatchery on the Amur River for the reproduction of herbivorous fish (grass carp, silver and bighead carp) with a capacity of 20 million pieces.
Chapter 1. Biological characteristics of herbivorous fish (white and bighead carp, grass carp)
Silver carp / Hypophthalmichthys molitrix / - a schooling freshwater pelagic fish that feeds on small floating algae throughout its entire life (except for the very early ones). The main systematic characters are: a rather tall body covered with very small scales; the head is wide; the eyes are located below the axis of the body (Fig. 1) (Vasilieva, 2004).
Silver carp has a number of morphological adaptations for feeding on phytoplankton. Thin, closely spaced gill rakers are connected to each other by transverse bridges, forming a “sieve” that allows small forms of algae and zooplankton to be filtered out. The algae retained by the gill mesh are compressed into a lump due to the interaction of the pharyngeal teeth, which are strongly compressed from the sides, covered with a cornea instead of enamel, and a millstone covered with a soft mucous membrane. Food in compressed form enters the intestine, the length of which in an adult silver carp exceeds the body length by 10-13 times (Russ, 1983).
The feeding characteristics of silver carp are determined by the structure of the filtration apparatus, as well as the composition and size of food organisms in the reservoir. Silver carp feeds mainly on phytoplankton and detritus. It switches to feeding on phytoplankton at a length of 1.5 cm, and before that it feeds mainly on zooplankton. All groups of algae are found in its food, but there is a certain selectivity in relation to different groups and types of algae. It prefers diatoms and green algae, but can effectively feed on blue-green algae, including macrocystis, a form that causes water blooms in reservoirs. The share of detritus in the diet of silver carp is 90% (Ponomarev, 2008).
Rice. 1 Appearance of silver carp
Silver carp is a valuable herbivorous fish. It reaches a length of 1 m and a weight of 16-18 kg. The age limit is over 20 years. The length of silver carp in commercial catches ranges from 20 to 75 cm, weight from 120 g to 5.6 kg, on average 41 cm and 1.2 kg.
The natural habitat of silver carp extends from the Amur basin to southern China. In Russia, it is distributed in the middle and lower reaches of the Amur (from the mouth of the Kumara River to the mouth of the Amgun), including in large lakes - Orel, Katar, Bolon. It is found in the Songhua, the lower reaches of Zeya, Ussuri, and in lake. Hanka. Recently discovered on Sakhalin (Safronov, Nikiforov, 1995). As an object of fish farming, it is widely distributed in the countries of Asia and Europe. Introduced into many reservoirs of Russia and the republics of the former USSR: reservoirs and lower reaches of the Volga, Dnieper, Dniester, Prut, Don, Kuban, Terek, the Aral Sea basin, lake. Balkhash and others, where natural spawning is observed in some cases. As an object of fish farming, it is grown in many ponds and reservoirs throughout the country.
Figure 2 shows the habitats of silver carp in Central Asia and Europe.
Fig. 2 Distribution of silver carp
In summer, silver carp feed mainly in the Amur channels and lakes. For the winter it moves to the Amur riverbed, where it lies in pits. The time to reach sexual maturity is determined primarily by the geographical latitude of the reservoir. Silver carp becomes sexually mature only at 7-8 years of age, reaching a weight of approximately 4 kg. Males usually mature a year earlier than females. Spawns during sharp rises in water level, releasing pelagic eggs. In the Amur, the main spawning grounds are located in the area from Khabarovsk and above. Spawning time is early June to mid-July.
Absolute fertility from 100 to 1500 thousand pieces. eggs, working fertility of females is about 500-700 thousand eggs. Spawning is portioned (up to three portions); at a water temperature of 25 °C, development lasts about 2 days. After swelling, the size of the eggs increases in diameter to 5 mm. Embryonic development in natural conditions. Cupid is carried out in the water column.
The hatched prelarvae are 5 mm long. Prelarvae located in the water column are passively carried downstream. After about 3-4 days at a water temperature of 20 - 23 0 C, the hatched larvae switch to a mixed diet and begin to actively swim. The larval period begins at the age of 7 days with a length of 6-8 mm (Nikolsky, 1974). In other reservoirs (China, Tsimlyansk Reservoir) only one portion of eggs can be spawned. Typically, spawning occurs in the early morning hours and is very violent, with spawners jumping out of the water (Reshetnikov, 2002).
Bighead carp / Aristichthys nobilis / - body shape similar to silver carp , but has a larger head, the eyes are set wider, the body is less high, the pectoral and pelvic fins, as well as the caudal peduncle are longer. The coloring is much darker; adult fish have dark spots on the sides of the body (Fig. 3).
Rice. 3 Appearance of bighead carp
Bighead carp is a Chinese species, common in the rivers of Central and Southern China. Previously not recorded in the Amur (Nikolsky, 1974). It came into this basin in the late 1950s from a number of Chinese fish farms located in the Sungari basin as a result of catastrophic floods. Subsequently, it spread widely throughout the Amur, where it is found from Blagoveshchensk to the Amur Estuary. Available in Ussuri and lake. Hanka. It is found in small quantities in the lower reaches of the Zeya and Amguni. Widely acclimatized in the European part of Russia (delta and reservoirs of the Volga, lower reaches and reservoirs of the Dnieper, Prut and pre-Dunai reservoirs, Dniester, Kuban, Don, Terek, Amu Darya, Syr Darya, Balkhash - Ili basin, etc.). As an object of aquaculture on the warm waters of state district power stations, nuclear power plants, and thermal power plants, they are grown much further north (Verigin, 1979).
Figure 4 shows the habitats of bighead carp.
Rice. 4 Distribution of bighead carp
This is a large fish, up to 146 cm long and weighing up to 32 kg. In the conditions of Turkmenistan, it reaches a weight of over 50 kg; in Cuba, individual specimens of the bighead carp weighed 60 kg. It is a heat-loving fish by way of life. The main food source is zooplankton, but by autumn the proportion of phytoplankton, including blue-green algae, increases in the intestines. Due to the nature of their diet, the intestines of bigheaded silver carp are shorter than those of white carp.
It matures in different reservoirs at different ages: In Turkmenistan it becomes sexually mature at 4 years, in Moldova at 4-6 years, in India at 2 years, in Cuba at 2-3 years, in the Moscow region at 5 years of life. Spawns during periods of sharp rise in water level, at the end of May. Absolute fertility 629-1 million. caviar. The optimal temperatures for the development of eggs are 16.5 -21 0 C. The eggs are bottom-pelagic, spawned in several portions.
Bighead carp is a valuable commercial fish. The meat quality is higher than that of silver carp. It is a promising object for pond and warm-water cultivation.
White amur/ Ctenopharyngodon idella / – has an elongated, ridged, striated body, covered with thick scales. It crushes food with powerful saw-shaped teeth located on the mandibular bones. The mouth is semi-inferior, the forehead is very wide (Vasiliev, 1985) (Fig. 5).
Rice. 5 Appearance of grass carp
Natural habitat is East Asia (China) from the Amur River south to Xijiang. In Russia it is found in the middle and lower reaches of the Amur (up to Blagoveshchensk), at the mouths of the Sungari, Ussuri and Lake Khanka. Widely introduced into water bodies of Europe, Asia and North America as an object of fish farming. For the purpose of acclimatization, it was released into many reservoirs of Russia (the Dnieper, Don, Volga, Kuban, Ural, Amu Darya, Syr Darya systems, Lake Balkhash).
The habitat of grass carp is shown in Figure 6.
Rice. 6 Distribution of grass carp
Grass carp is characterized by rapid growth; in the Amur basin it reaches a length of 1.2 m and a weight of 40-50 kg. In natural conditions, yearlings have a length of 20–25 cm and a weight of up to 600 g; after 2 years, the mass of grass carp reaches 2.4–3 kg. The fastest growth is recorded in the tropical zone, where two-year-olds can reach a weight of 14 kg (Bagrov, 1985).
Makes seasonal migrations. In the summer, it fattens up in the accessory system, and in the winter it goes out into the river bed and stays in the pits.
Juvenile carp consume zooplankton (crustaceans, rotifers, chironomids), adult fish are narrow stenophages, feeding mainly on higher aquatic vegetation (including terrestrial vegetation, flooded by summer monsoon floods), grinding it with serrated pharyngeal teeth. In the south of Russia, grass carp also uses tough vegetation (reeds, cattails) for food. At the same time, it willingly consumes terrestrial plants (clover, alfalfa, cereals).
In the Amur basin it becomes sexually mature at the age of 9-10 years with a length of 68-75 cm, in the rivers of China - 1-2 years earlier, in Cuba they mature at one year of age, females a year later. The daily diet, growth rate, and sexual maturation depend on the water temperature. Spawns pelagic eggs in portions. Fecundity in females ranges from 237 to 1686 thousand, with an average of 800 thousand eggs. Spawning is portioned, greatly extended from April to August at a temperature of 23-28 0 C, the main spawning grounds are located in the Songhua River. Eggs are usually spawned in the upper layers of water during periods of sudden rises in level caused by heavy rainfall. Fertilized grass carp eggs are bathypelagic, their specific gravity is somewhat heavier than water, and is sensitive to the quality of the water and the content of dissolved oxygen in it. The incubation period lasts 18-72 hours. The larvae hatch after approximately 3 days with a length of 6.9 mm. Subsequently, the larvae migrate to the coastal zone and into shallow bays, having reached a length of 2.5–3 cm and begin consuming vegetation.
The development of herbivorous fish is divided into embryonic, larval and juvenile periods.
The eggs are pelagic, transparent, with a diameter of 3.5 - 4.5 mm. The egg shell is represented by only one primary (proprietary) shell - the zona radiata.
The embryonic period includes 8 stages of 22 stages.
Stage I. Watering of the cavity between the egg membrane and the egg (appearance of the perivitelline space) and formation of the blastodisc (stages 1-3).
II stage. Fragmentation of the blastodisc from two blastomeres to the blastula inclusive. In this case, predominantly quantitative changes occur: an increase in cells and a decrease in their size (stages 4-10).
III stage. Gastrulation is the formation of germ layers. Accompanied by fouling of the yolk sac with blastoderm (stages 11-13).
IV stage. Organogenesis is the differentiation of germ layers into the rudiments of the main organs (nervous system, notochord, muscles, intestines, eyes, auditory vesicles, etc.) (stages 14-15).
V stage. Separation of the tail section of the embryo from the yolk sac, the beginning of mobility of the body of the embryo (stages 16-18).
VI stage. Hatching of the embryo from the shell (stage 19).
VII stage. Appearance of a developed embryonic vascular system (stage 20).
VIII stage. The appearance of the movable gill-maxillary apparatus and the beginning of the functioning of the gills (stages 21-22).
The larval period includes 5 stages, 8 stages.
I stage. Mixed endogenous-exogenous nutrition of the larva (23-24 stages).
II stage. The larvae feed exclusively externally – exogenous (stage 25).
III stage. Formation of unpaired fins (stage 26).
IV stage. The appearance of the second section of the swim bladder and the formation of pelvic fins (stage 28).
V stage. Formation of fin rays in paired pectoral and ventral fins (29-30 stages).
The juvenile period includes 2 stages.
I stage. The beginning of the laying of scales.
II stage. Malek with developed scales.
Chapter 2. Choosing a location for the construction of a fish hatchery
The source of water supply for the designed fish hatchery for the reproduction of herbivorous fish is the Amur River, which is formed by the confluence of the Shilka and Argun and is divided into 3 parts - the upper (to the mouth of the Zeya), the middle (to the confluence of the Ussuri) and the lower (to the Amur Estuary). In the upper section of the banks of the Amur, they are high and covered with forest; below the mouth of the Zeya, the Amur flows through the lowlands and after the confluence of the Bureya again acquires a mountainous character. Coming out of the mountain gorges, the river expands, forming channels and islands. After the confluence of the Ussuri, the wide Amur flows through a hilly, sometimes swampy lowland. When it flows into the Gulf of Tatar, the river forms an estuary in which the Amur has an underwater delta. The Amur River basin is located in the temperate latitudes of East Asia.
Within the Amur basin there are four physical-geographical zones: forest (with subzones of coniferous-deciduous forests, middle and southern taiga), forest-steppe, steppe and semi-desert (with a northern subzone of semi-deserts and a subzone of dry steppes).
The length of the Amur is 2824 km, the basin area is 1,855,000 km 2, the height of the source is 304 m, the water flow is 11,400 m 3 /s.
The Amur is fed primarily by rain, which accounts for up to 64% of the annual runoff, snow cover accounts for 19% of the runoff, and groundwater accounts for 17%. There is no clearly defined spring flood in the Amur, and the river reaches its maximum levels during the summer monsoon rains. The Amur is under the ice from November to late April - early May. Level fluctuations in the river bed relative to low water range from 10-15 meters in the upper and middle Amur and up to 6-8 in the lower Amur. Moreover, during the heaviest rainfalls, spills on the middle and lower Amur can reach 10-25 kilometers and last up to 70 days.
The soils in the area where the enterprise is being built are floodplain and mountain forest (brown and gray). Peat soils have deeply decomposed plant residues, have a high ash content (from 8 to 70%), they are moderately acidic, with average saturation with bases. With appropriate reclamation measures, soils can be turned into tracts of fertile land. The Middle Amur part is not yet fully exploited, but due to soil and climatic conditions it is a promising agricultural area.
The river regime reflects the climatic conditions of the region, and according to the conditions of the water regime, they are classified as the Far Eastern type with a well-defined predominance of rain runoff. The monsoon climate determines the predominance of summer-autumn flow and the subordinate importance of spring flow for most of the rivers in the region.
The amount of annual precipitation ranges from 250-300 millimeters in the most arid southwestern part of the Amur source basin and up to 750 millimeters in the southwestern part of the Sikhote-Alin ridge.
The construction of a fish hatchery is planned to be carried out in the middle reaches of the Amur, in the area of the city of Blagoveshchensk, a few kilometers from the village of Konstantinovka.
Proximity to populated areas ensures the supply of labor and electricity. Highways pass through the nearest villages; a railway starts from the village of Poyarkovo, 20 kilometers from the site.
The location of settlements and the site for the construction of a fish hatchery is shown in Figure 7.
Scale: 1 cm 25 km (1:2 500 000).
Legend:
Highway; - source of water supply;
Railway; - site for the construction of a fish hatchery
Locality
Rice. 7. Map of the location of the designed fish hatchery
The choice of location for the fish hatchery is justified by the absence of a dam, the presence of transport routes for communication with the enterprise, the proximity of settlements (Konstantinovka, Poyarkovo, Muravyovka, Korshunovka, Nizh. Poltavka, Novoaleksandrovka, etc.), which has an important role in providing electricity and labor. It is also important to note that in the water intake area and in the reservoir section at a distance of 20 km there is no discharge of wastewater from industrial and agricultural enterprises, and there is also a sufficient amount of water suitable for artificial reproduction purposes.
Chapter 3 . Physico-chemical and hydrological characteristics of the water supply source
The Amur River is a Far Eastern river with an extensive network of tributaries. The largest tributaries of the Amur are the Gilchin, Dim, Zavitaya, Bureya, Zeya, Arkhara, Uril, and Belaya. And also in the Amur region there are 50 lakes with an area of more than 500 hectares, the level of which is subject to sharp fluctuations throughout the year depending on the level regime of the Amur. According to the degree of connection with the Amur, all lakes are divided into 3 groups. The first group is floodplain type lakes with silted soils and low-lying shores, which have a close connection with the Amur (Petropavlovskoye, Innokentyevskoye, Hummi). The second group is lakes connected to the Amur by channels (Bologne, Kizi, Kadi). The third group is lakes almost isolated from the Amur (Evoron).
Hydrological characteristics.
The Amur belongs to the rivers predominantly fed by rain. The share of rainfall accounts for from 75 to 85%, snow - from 7.5 to 22%, underground - from 2.5 to 7.5%. Due to the predominance of rainfall, river flow is extremely uneven throughout the year. Thus, in the annual flow, winter flow (November - March) is 3-7%, spring flow (April - May) - 15-20%. The highest flow is observed in the summer-autumn season and amounts to 75-80% (Karasev, Khudyakov, 1984). . The water regime is characterized by floods in warm seasons, caused by heavy rains. It is characterized by high water content, the average annual flow is 886 m 3 /sec.
The climate is transitional from monsoon to continental. Monsoon patterns mainly manifest themselves in the intra-annual distribution of precipitation. On coasts washed by cold currents, thick fogs are often observed. The amount of precipitation varies from 350 mm to 800 mm, and in summer it is 60 times more than in the winter months. In 2 months, in July and August, about six months' worth of them falls.
The speed of water flow in the river varies - during heavy floods it reaches 3-4 m/s, in the middle part 2-3 m/s, and near mountain streams 5-6 m/s.
Physical characteristics.
The determining factor is temperature.
The change of oceanic and continental influences is expressed in the nature of the thermal regime. Summers here are moderately warm and rainy, winters are cold and with little snow. In summer, temperatures range from +12 in June to +18-20 in July-August. In winter, from -13 at the end of December to -20 in January.
Ice formations in the form of banks and grease usually appear in the second half of October. The river freezes in mid-November, in some areas earlier. The Amur opens at the end of the third ten days of April. Ice movements and break-up occur at levels more or less equal in height; spring ice drift occurs relatively calmly.
Chemical characteristics.
The Amur is characterized by a high self-purifying ability, a positive biological balance and, as a result, sufficient oxygen content, which ranges from 5 to 6 mg/l.
The pH of the water in the river can change in the annual, seasonal and even daily cycle, but the neutral or slightly alkaline reaction of the water predominates (pH 6.5-7.5).
The amount of suspended particles carried by the Amur is small, the average turbidity is low, 107 g/m 3 . The river basin is located within the turbidity zone from 50 to 150 g/m3. The greatest turbidity is observed in spring. Due to the high flow rates, the transfer of substances is high here.
Chemically, the river is characterized by low mineralization and mostly belongs to the hydrocarbonate class; sometimes there are waters of hydrocarbonate-sulfate-calcium composition. The mineralization of river waters fluctuates throughout the year and varies depending on the place of flow through the territory. Over the course of a year, the Amur carries an average of 18.7 million tons of dissolved substances, which is 54 mg/l. The ionic composition is as follows: Ca – 7.4 mg/l, Mg – 1.6, Cl – 8.0 mg/l.
The concentration of iron in the waters is from 20 to 50 mg/l, manganese - 1.5-11 mg/l, and has a low content of fluorine, copper, cobalt and other trace elements. At a number of deposits, water is purified from iron.
Thus, the water quality of the water supply source of the designed fish hatchery, i.e. Cupid meets the biological requirements of herbivorous fish (silver carp and grass carp), since the most preferred temperature for their development is t = 18-22 o C. Optimal pH = 7.0-7.5. Herbivorous fish belong to the group of fish that can easily tolerate a decrease in oxygen to 5 mg/l.
CHAPTER 4. Description of the technological process of the fish hatchery
A fish hatchery is an enterprise engaged in the cultivation of fish seeding material: fingerlings and yearlings of semi-anadromous and aquatic fish species, including herbivorous ones.
The designed fish hatchery is planned to be built on the banks of the Amur River. It includes pre-spawning, fry, nursery ponds, and an incubation facility.
4.1. Harvesting and obtaining mature producers
Herbivorous fish (white and bighead carp, grass carp) are important objects of pond fish farming and are used to form the ichthyofauna of rivers, lakes, and reservoirs.
The first link in the chain of work on the artificial reproduction of herbivorous fish is the purchase of producers.
It is planned to stock the spawners in May in the Zee tributary of the Amur River and deliver them to the fish hatchery in slots. Healthy, intact breeders (without wounds, bruises, bruises, cuts) at the age of 6-7 years weighing 5-6 kg are selected and old breeders are discarded.
Producers are treated with a 5% solution of table salt and planted in pre-spawning ponds. The area of pre-spawning ponds is 0.05 - 0.5 ha, depth 1.5-2.0 m, they must quickly fill with water and drain. The planting density of herbivorous fish producers in them is up to 1600 fish/ha. It is necessary to ensure constant water exchange in these ponds to prevent excessive heating of the water. Pre-spawning maintenance lasts 30-45 days. This period is important in the life of producers due to the fact that during the pre-spawning period the last phases of oogenesis end, on which producers spend a large amount of energy materials. To catch spawners, pre-spawning ponds are lowered. Then fish ready for spawning are selected using fabric sleeves, placed in stretchers with water or canvas vats and transferred to injection ponds.
Individuals are sorted into groups according to the degree of readiness for spawning, exterior, and sex. Females are divided into 3 groups. The first group is the best, mature females with a saggy and soft abdomen, with swelling in the genital area, they are used primarily for work. The second group is females with similar characteristics, but less pronounced. They are used after finishing work with females of the first group. The third group is females, which do not differ in appearance from males; they are not used for caviar production (they are planted for summer feeding).
Males are divided into two groups: 1) those that give off milk easily; 2) secreting very little milk or non-flowing. They are used at the end of the season or not used for reproduction. Males differ from females in the presence of spines on the pectoral fin on its inner surface. They are sharpest in silver carp, less sharp in bighead carp, and in grass carp they are very small.
Breeders of herbivorous fish are ready for spawning in mid-May - early June.
To accelerate the maturation of reproductive products, producers are stimulated using an ecological-physiological method, which consists of providing conditions as close as possible to natural ones (t = 18-22 o C, pH = 7-7.5, O 2 content = 5-6 mg/l), as well as in the administration of a physiological preparation of the pituitary gland.
The pituitary gland, or inferior cerebral appendage, is an endocrine gland located at the base of the brain. The pituitary gland releases hormones into the body's circulatory system. The pituitary gonadotropic hormone regulates oogenesis and spermatogenesis, causes maturation of germ cells, ovulation and sperm formation. The gonadotropic hormone secreted by the pituitary gland enters the blood and stimulates the maturation of germ cells, as well as the release of mature eggs (eggs) from the follicles and the formation of sperm. During spawning, fish producers spawn mature reproductive products not all at once, but gradually. So, the female spawns eggs into the water as they ovulate. The movements made by the female lead to the rupture of the next follicles and the continuation of the release of eggs.
Before starting work on injecting producers, the prepared pituitary glands of carp, carp or crucian carp (you can also use a substitute - choreogonic gonadotropin) are ground in a porcelain mortar into powder, then poured with physiological solution (65 mg of table salt dissolved in 100 ml of distilled water) and mixed thoroughly. The resulting suspension of the pituitary gland is injected using a syringe into the spinal muscles of the producers. In this case, the dose of the pituitary gland injected into the fish is determined by the quality of the resulting reproductive products. An insufficient amount of pituitary gland does not ensure the maturation of the gonads, and an excess amount sharply reduces the quality of the resulting reproductive products.
An aqueous suspension of the pituitary gland is injected into the back muscles of the first third of the body (at an acute angle to the surface of the body) above the lateral line and below the base of the dorsal fin using a Record syringe. The needle is inserted under the scales. After removing the needle, the injection site is pinched with a finger to prevent the suspension from leaking out and lightly massaged. This work is carried out in a canvas stretcher with water.
Females with gonads in the completed fourth stage of maturity are given a preliminary pituitary injection at the rate of 3 mg of dry pituitary gland weighing 5-7 kg, and 5-6 mg of the drug for larger females. A day after the preliminary one, a permissive injection of 3-6 mg of the drug per 1 kg of female weight is made, depending on the size of the gonads, and males are also injected. Males weighing 5-7 kg are injected with 4-6, larger ones - up to 10-12 mg of pituitary dry matter per fish.
Dosages are calculated per 1 kg of fish weight, taking into account water temperature (Table 1).
Table 1
Required amount of pituitary gland preparation for producers of herbivorous fish
| Water temperature during ripening period |
Dose of the drug per 1 kg of weight, mg |
Ripening time, h |
The time of injection of producers is chosen taking into account the water temperature and the rate of maturation of females, so that the receipt and insemination of eggs, their placement in devices for incubation, occur during daylight hours.
The preliminary injection is carried out, as a rule, at 18-19 pm, allowing - from this time onwards. However, during sudden cold spells at night, injections are sometimes carried out in the morning. The rate of maturation of females after a permissive injection strongly depends on the water temperature and is determined as follows: at a temperature of 20-22°C, maturation occurs after 10-12 hours, at 23-25° -9-11, at 26-28°C - after 7 -10 hours
On the second or third day, males are injected 1 hour before the permissive injection is given to females.
6-9 hours after the injections, they begin to regularly check the state of maturity of the producers. The interval between these checks is determined depending on the temperature of the water during the day, the age and condition of the producers, but cannot be more than 1.5-2 hours. This is due to the danger of overripening. For the convenience of work, it is advisable to group producers of different sizes, origins, and degrees of maturity. Dissimilar breeders are examined by transplanting them into a free cage or container filled with water. Determining the exact time of ripening is very important. The maturation of reproductive products occurs 10-12 hours after the permissive injection (at a water temperature of 20°C) (Kozlov, 1980).
4.2. Obtaining germ cells, insemination of eggs, preparing eggs for incubation
Sexual products from producers of herbivorous fish (white and bighead carp, grass carp) are obtained by straining. Mature females are caught from the cages, thoroughly wiped with gauze, and the head and anal fin are wrapped in a dry cloth. The head of the fish is pressed with the elbow of the left hand to the body, and with the hand of this hand the tail stalk is held in such a position that the genital opening is above the edge of a clean dish (enamel or plastic basin), and the abdomen is slightly curved outward. Due to the pressure of the walls of the abdominal cavity, part of the caviar is released from the genital opening, falling on the edge of the dish and flowing to the bottom. Do not allow eggs to directly fall on the bottom of the dish, as they are easily damaged. After the free flow of eggs has stopped, the female’s abdomen is slightly squeezed and massaged with the fingers of the right hand towards the anal fin. When lumps of caviar and drops of blood appear, straining is stopped.
The amount of caviar is calculated by volumetric or weight method. Volumetric method: take three control samples of 50-100 ml each, count them and find the average number of eggs contained in 1 ml. Then use a measuring cup or mug to measure the volume of all collected caviar. The total volume is multiplied by the average number of eggs in 1 ml and the amount of collected eggs is obtained in thousand pieces. Weight method: caviar is collected in tared basins, pre-weighed. After straining the caviar, the basin with it is weighed again, and the mass of the caviar is determined from the difference in mass. Three samples of 10 g each are taken from the basin, the number of eggs in each sample is determined and the average amount in 1 g is found. Then the mass of collected eggs is multiplied by the average value found and the total number of eggs in pieces is obtained. The fertility of female grass carp and silver carp ranges from 10 thousand to 2 million eggs.
Sperm collection from males is also carried out by straining, massaging the abdomen. Then it is placed in separate test tubes for 30-60 minutes. Before receiving caviar, store them in a thermos with ice.
Determination of sperm quality is carried out visually. Good quality sperm has the consistency of cream, moderate thickness and white color. The quality of sperm is determined by measuring the volume of ejaculate, the duration of sperm movement, and the ratio of live and dead sperm. The caviar must be intact, have a certain size and color.
The eggs are inseminated using the dry method. Eggs from 3-5 females, moistened with cavity fluid, are expressed into a clean container. Then sperm from 2-3 males is poured into it, carefully stirring with a goose feather. Add a little water, pause for 2-5 minutes. For 1 kg of caviar, 5 ml of sperm is used.
The caviar of herbivorous fish is weakly sticky, so before placing it in the incubation apparatus, it is not de-glued; it is washed with water to remove organic matter for 5 minutes.
4.3 Egg incubation
Incubation of eggs of herbivorous fish will be carried out in incubation apparatus “VNIIPRH”, with a capacity of 200 l (Fig. 8).
Rice. 8. Incubation apparatus “VNIIPRH”
1-drain pipe; 2-incubation tank; 3-feed pipe.
The apparatus is a vessel made of organic glass, consisting of an incubation tank, supply and drain pipes.
The optimal water temperature during incubation should be 22-25°C, and the oxygen content in the water of the apparatus should be at least 4 mg/l. The survival rate of larvae from eggs is 50%. At the moment of loading caviar, the devices should be filled with water to 1/3 of the volume, and the water supply to the devices should be stopped. Temperature and oxygen conditions are of decisive importance when incubating eggs. After loading the caviar, the flow rate is set to 4-8 l/min. In water, caviar quickly swells and after 5-6 minutes its volume doubles. The swelling process of caviar is completed after 2 hours. After this, the optimal water flow in the incubation apparatus is established. Incubation of eggs at a temperature of 21-25 ºС lasts 23-33 hours.
Caring for eggs during incubation involves monitoring their development, regulating the water supply to the incubation apparatus, and collecting dead eggs. A siphon should be used to remove dead eggs, which are concentrated in the form of a cloudy white layer above the live eggs. 3-5 hours before the hatching of prelarvae, 100-150 eggs are viewed under a binocular and the percentage of normally developing embryos is determined.
With high quality eggs and normal incubation conditions, the yield of free embryos of herbivorous fish is at least 70-80% of the amount of eggs laid for incubation.
4.4 Maintenance of prelarvae and their rearing
4.4.1. Maintenance of prelarvae. The prelarvae will be kept in ventilators-2 (Fig. 9).
Rice. 9. Ventilator-2
1-protective sieve; 2-drain pipe; 3-capacity; 4-water flow divider; 5-supply pipe; 6-hermetic valve.
It is a cylindrical container made of organic glass with a volume of 200 liters with water supply and drainage pipes, in the lower part of which a water divider is attached, and in the upper part a protective mesh is installed. The water entering the apparatus forms a spiral-shaped upward flow, simulating the flow of a river. In these conditions, close to natural, aging takes place with virtually no waste. The protective mesh is stretched over a metal frame and tightly installed in the apparatus for the holding period.
The duration of keeping the larvae depends on the water temperature and is 90-100 hours at 18-20°C, 80-85 hours at 20-23°C, about 50 hours at 26-27°C. Under normal conditions, the survival rate of larvae that have passed for mixed feeding, is 50% of the number of fertilized eggs. After resorption of the yolk sac, they feed on the yolk and small crustaceans, which they find in the warm water of the pools. 2-3 hours before sending for rearing, the larvae are counted by counting 2-3 samples (200-300 ml of a mixture of larvae with water) and further recalculating the entire volume of the container used to keep the larvae.
The final product of the hatchery workshop is larvae that have switched to a mixed diet. Larvae at this stage of their development are characterized by increased sensitivity to changes in external conditions. Therefore, it is currently practiced to raise the larvae of herbivorous fish to more viable stages.
4.4.2. Raising larvae. Raising larvae that have switched to a mixed diet to a weight of 25-30 mg ensures a reduction in the waste of juveniles in the early stages of development and during further rearing. Factors such as food supply, oxygen regime and water temperature are of primary importance.
The rearing of larvae of herbivorous fish is usually carried out in fingerling ponds with an area of up to 1 hectare and an average depth of 1 m. The water temperature in the ponds during the rearing period should be at least 20 0 C in the morning, the optimal oxygen content is 6-12 mg/l, the concentration of the required food is 1000- 1500 copies/m3. A litter trap made of a metal mesh with a mesh of 0.5-1.0 mm (or covered with a nylon sieve No. 32) is installed on the water supply structure of the pond, and on the discharge structure - a fry catcher made of a nylon sieve.
After transplanting the larvae into the fry ponds, mineral fertilizers are applied at the rate of 50 kg of ammonium nitrate and 20 - 25 kg of superphosphate per 1 ha. Good results are obtained by adding an aqueous mixture of manure and mineral fertilizers to ponds. To do this, 1 ton of manure is mixed with 40 kg of superphosphate and 100 kg of ammonium nitrate, diluted in 10 volumes of water and infused for one day. The shaken mixture is brought in buckets along the water's edge. An abundance of food organisms can be quickly achieved by adding hydrolysis mass, prepared from last year's vegetation in wooden barrels, to the ponds. The hydrolysis mass is also applied in shallow water. The liquid remaining in the barrels is used to water sheaves of withered vegetation placed along the water edge of the fry ponds.
The need for a certain composition of food organisms is different for the larvae of all three fish species. Thus, silver carp larvae in the early stages of development feed on small forms of zooplankton, later they switch to consuming larger forms of food organisms, as well as phytoplankton. The larvae of bighead carp and especially grass carp have a wider range of nutrition. Thus, their diet at later stages of development is dominated by small, large and predatory forms of zooplankton.
Growing is carried out within 14-20 days to a weight of 300-500 mg. Waste during the growing period in fry ponds is 40%.
4.5 Raising juveniles.
The rearing of juvenile herbivorous fish will be carried out in nursery ponds with an area of 30 hectares, with a stocking density of 30-40 thousand fish/ha. The juveniles are raised in nursery ponds until autumn. Before planting in nursery ponds, larvae are counted using the reference method. A certain number of larvae are caught in a special basin (standard). Then the larvae are caught in a basin of the same volume without miscalculation. When the density in the 2 basins becomes the same, record the number of larvae. The number of cans is taken into account and, knowing how many larvae are in the standard, they are converted to the total number.
Nursery ponds must have a well-planned bed and be equipped at the water supply with litter traps made of mesh with a mesh diameter of no more than 1 mm. Ponds are prepared in advance during operation. After drying, reclamation work is carried out in them: fish and drainage ditches are cleaned and deepened, hydraulic structures are repaired, dry vegetation is removed, and plowing is carried out in heavily overgrown areas. To create optimal conditions for the development of a natural food supply, rotted manure is introduced into the ponds 30-40 days before the ponds are filled. It is evenly distributed, followed by disking at 5-7 cm.
Juvenile herbivorous fish are placed in nursery reservoirs no later than 7-10 days after they are flooded. Planting juveniles in gradually filled ponds with meadow vegetation at the bottom is very effective. Gradual filling of them contributes to better heating of the water and good development of the food supply for the larvae.
After filling the nursery ponds with water, it is necessary to regularly add mineral fertilizers to them. During the growing process, to increase the biomass of phyto- and zooplankton, ammonium nitrate is added every 2 weeks - 60 kg/ha, superphosphate - 50 kg/ha. If there is a lack of vegetation in the nursery ponds, mown terrestrial plants are brought in to feed the carp on floating wooden frames.
It is necessary to regularly monitor the state of the aquatic environment, the growth rate and physiological state of the fish. Every day at 7, 13 and 19 o'clock the water temperature is measured with a mercury water thermometer at a depth of 20-30 cm at the bottom drainage outlet. The content of oxygen dissolved in water during the first growing period is determined every 10 days, from the second half of June - every 5 days, and during periods of persistent decrease in its content to less than 4 mg/l - daily. At least once a decade, the active reaction of water (pH) is determined. Water transparency is monitored once every three days. Control catches are also carried out every ten days in 2-3 characteristic areas of the pond. Since juvenile herbivorous fish are easily injured, they must be caught using a large fish catcher.
Juvenile herbivorous fish weighing 20 g are counted and released into natural reservoirs. The mortality rate of juveniles in nursery ponds is 30-50%.
4.6 Counting and releasing juveniles.
The reared fry are counted before release into the reservoir using a continuous weight method. All grown juveniles are lowered using Eliseev devices installed in the airlock bay. This apparatus is a wooden tray, the middle section of the bottom of which is covered with a mesh. The width of the tray is equal to the width of the gateway span. At the end of the tray there are grooves into which a mesh stand with a mesh frame is inserted, which prevents the fry from leaving the tray. The water flowing out of the pond flows through the tray and the bulk of it is discharged through a section of the mesh bottom, and the juveniles are retained in a small layer of it. A tub with mesh walls suspended on a block is placed under the stand. Having lifted the mesh frame, the juveniles are thrown into this tub with a small layer of water. A tub filled with juveniles is weighed on a dynamometer, and another tub is placed under the apparatus. The juveniles are then released into the drainage canal. The mass of fry in each tub determined on a dynamometer is recorded in a log. Every 2 hours, a small control sample is taken and weighed. The sample is analyzed according to size and species composition. Then the number of juveniles is counted individually and the average weight of one specimen is determined. Having established the number of juveniles in the sample taken and knowing the total mass of the juveniles released in 2 hours, they recalculate the number of juveniles released during this time.
To transport juvenile herbivorous fish, live-fishing machines will be used with a fish-to-water ratio of 1:4. Transport containers for transporting fish must have sleeves for quick release of water and fish. It is convenient to use polyethylene pipes and other devices for unloading fish. Live fish machines must have containers in which the required temperature and gas conditions are maintained. When fishing and transporting, it is necessary to avoid injuries.
The release of juveniles will be carried out into the waters of a tributary of the river. Amur - Bureya, as this will ensure maximum survival of young of the year due to the good supply of this river with the food supply needed by herbivores - phyto- and zooplankton. Also in this area there is no harmful influence of polluted wastewater.
In experiments by ecologists, grass carp, considered an exclusively herbivorous fish, preferred freshwater amphipods to its favorite algae.
Like land animals, fish are divided into carnivores, herbivores, and omnivores. Although it seems clear that different fish will prefer different underwater vegetation, there has been little detailed research on this topic. Elisabeth Bakker from the Netherlands Institute of Ecology set out to find out the tastes of two fairly common freshwater fish, rudd and grass carp. Both were offered five types of algae, the weight of each “dish” was measured before and after the experiment to find out what the fish liked most.
Grass carp, avowed vegetarian and secret predator (photo by cotaro70s).
At first, the results were very banal. The fish paid the least attention to algae with toxins, and most readily ate species rich in nutrients, preferring those that contained the maximum nitrogen. But then something unexpected turned up. Along with algae, the fish were offered amphipods. And when the fish had to choose between their favorite algae and crustacean, they ate the animal “snack” first.
In the case of the rudd, this is not so surprising - this species is considered an omnivore. But grass carp, a strict vegetarian, is believed to have behaved in exactly the same way. Ecologists published the results of the experiments in the journal Freshwater Biology.
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Why grass carp suddenly switched to meat remains a mystery. The choice, however, cannot be called unsuccessful: amphipods are definitely richer in organic nitrogen than underwater vegetation. Perhaps, the authors of the article argue, there are no strict herbivores under water at all, and all so-called vegetarians periodically diversify their menu with animal food.
One way or another, these data allow us to reassess the role of grass carp in freshwater ecosystems. This species is often used as an effective environmental tool to keep algae under control so that it does not overwhelm the entire body of water. Now fish farmers and ecologists have to think about what else grass carp can eat, freeing the reservoir from excess algae.
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