Technology of artificial fertilization and de-adhesion of carp fish eggs

The roe from each female is milked into a separate container, and the volume of the collected roe is determined. The collected roe does not lose its fertilization capacity for 30–45 minutes. The dish containing the roe is covered with a thick, damp cloth. Immediately after milking the roe, work with the males begins. Given that the sperm quality in fish varies, the sperm from each male is milked into a separate container, and the quality of the milt is determined.

A small drop of milt is placed on a microscope slide, and a large drop of water is placed next to it. Observing under a microscope at low magnification, the drop of milt is joined to the water with a dissecting needle. Upon entering the water, the spermatozoa become motile and rapidly spread throughout the drop of water. The degree of sperm motility is determined on a five-point scale. Sperm in which all spermatozoa are motile and the majority exhibit forward movement is considered good. Its quality is rated at 4 or 5 points, and it is suitable for fertilizing roe. Sperm in which forward movement is observed in only a small portion of spermatozoa, while the bulk of them exhibit only oscillatory movements or remain stationary, is unsuitable for fertilization.

Good quality sperm resembles cream in appearance and consistency. Milt retains its fertilizing capacity in a refrigerator for about 1.5 hours. For fertilization, the roe is mixed with milt at a rate of 3–5 ml of milt per 1 liter of roe. Under production conditions, milt is taken from 2–3 males. The roe and milt are combined without pre-adding water and are thoroughly mixed with a bird feather. Fertilization of the roe occurs in a detaching solution.

The detaching of roe in Weiss jars is carried out using bubbling (passing small air bubbles through the detaching solution).

Figure 24 – Detaching of roe in Weiss jars

The device for detaching roe using air consists of three elements:

• a source of compressed air;
• an oil filter;
• an air distribution pipe with valves.

Compressors of various designs can be used as the air source. The air distributor can be portable or mounted together with the stand for the Weiss jars.

The technique of detaching is very simple. 2 liters of detaching liquid, talc suspension, or a mixture of cow milk and water (1:5) are poured into the Weiss jars, and the compressor is turned on. Then, the jars are loaded with fertilized roe, and using the valves, an air supply rate is set such that the roe is intensively mixed but not splashed onto the walls of the jars. If roe gets onto the walls, it is shaken off with a bird feather. One compressor capable of delivering air at a pressure of 2–3 atm can support the operation of more than 50 jars.

During the process of detaching the roe (as it swells), detaching liquid is added to the jars. If the roe has not detached sufficiently, it must be quickly transferred back into the detaching solution and the air turned on. After 15–20 minutes, the roe is completely detached. After the detaching process is completed, the roe is transferred to incubation jars.

Before loading the roe, a weak water flow (0.5 l/min) is set in the Weiss jar. Then, three-quarters of the water is siphoned out of the jar, and without stopping the flow, the roe is poured from the basin where it was detached. On average, 500 thousand fertilized eggs—approximately 500 g—are placed in each jar.

After the fertilized roe is placed, the water flow into the jar is carefully increased to 4–8 l/min so that the entire mass of roe is mixed slowly but continuously—even a short-term cessation of flow or local stagnation of roe in the jar can lead to mass mortality due to suffocation. From the second day of incubation, unfertilized and dead eggs appear above the layer of living, developing roe. Dead roe is regularly collected with a siphon.

At water temperatures above 20 °C, the development of roe occurs faster than the development of the *Saprolegnia* fungus, so treating the roe with agents to suppress *Saprolegnia* is optional. At temperatures below 20 °C and a low percentage of roe development, it is advisable to use the dye malachite green, which allows for the destruction of *Saprolegnia*. For this purpose, the water supply to the jar is turned off. After the roe has settled (3 min), half of the water layer above the roe is drained from the jar. Then, 10 ml of a 0.05% malachite green solution is added for every liter of the jar's contents. The contents of the jar are thoroughly mixed with a feather and left for 20–30 minutes, after which the water supply is turned on. Such roe treatment is performed once every 2 days or more frequently, depending on the condition of the embryos.

The duration of development of fertilized roe depends primarily on temperature conditions. A specific sum of heat is required for the full development of roe and larval hatching. Optimal temperature for embryo development is 20–22 °C. Duration of roe development (days) at different temperatures:

The carp embryo goes through several stages in its development. There are a number of critical moments when embryos are most sensitive to changes in external conditions and may perish. Particularly high sensitivity of the roe is observed at the beginning of blastodisc cleavage, at 3–6 hours after fertilization. At this moment, sharp fluctuations (more than 2 °C) in water temperature are unacceptable.

A critical moment in the development of carp embryos is associated with gastrulation, which begins 9 hours after fertilization, resulting in the formation of three germ layers: ectoderm, mesoderm, and endoderm. In this regard, it is most appropriate to evaluate preliminary incubation results after the completion of this stage. One day after fertilization, the embryo's body covers about 3/5 of the yolk circumference in a horseshoe shape. Body segmentation is visible. At 35–45 hours of age, the embryo begins to move slightly. Upon completion of body segmentation, black pigment appears in the eyes, and the tail section becomes distinct. Two days after fertilization, formed elements appear in the embryo's blood, the pectoral fin is visible, and the embryo rotates actively within the envelope. At this stage of development, it is most convenient to transport embryos in isothermal containers, where some cooling is possible to slow down development. After 3 days of incubation at a temperature of 20–22 °C, the hatching of larvae begins, shortly before which increased embryo mortality is observed.

To accelerate hatching, the water flow rate is reduced to 0.2–0.5 l/min. If the moment is chosen correctly, complete hatching is finished in 20–40 minutes. The acceleration of hatching with a sharp decrease in water flow is associated with the accumulation of hatching enzyme in the water, which causes the weakening of the egg membranes. After restoring the flow, the larvae are carried out of the apparatus by the water current and caught in collectors made of No. 17 bolting cloth or immediately sent via a hose to rearing tanks or holding apparatuses.

Larval holding is carried out in tanks made of No. 17 bolting cloth measuring 50 × 60 × 45 or 45 × 45 × 45 cm. Each tank can hold 250,000 or 150,000 larvae, respectively. They are very sensitive to oxygen deficiency; therefore, the water flow rate in the pool must be at least 1 m³/h per 1 million larvae. To improve water exchange, bottom water supply to the tanks via spray bars or nozzles is provided. The holes of the spray bar or nozzle are made 15 cm from the bottom of the tanks.

Depending on the water temperature, larvae are held in tanks for 2–4 days. The transition to external feeding in carp larvae coincides with the moment the swim bladder fills with air. No later than one day after the start of swim bladder filling, the larvae are stocked into ponds for rearing. During holding in tanks, the larvae are not fed.

Larvae with a filled swim bladder are stocked into ponds within 24 hours. For short-distance transport, polyethylene bags filled 2/3 with water and oxygen are used; the stocking density in this case is 200,000–300,000 individuals per bag. For long-distance transport, live-fish transport vehicles with a compressor are used, or they are sent by air in polyethylene bags with water and oxygen.

When releasing larvae into ponds, it is necessary that the water temperature in the transport container and in the pond does not differ by more than 2 °C. It is recommended to place juvenile fish in areas of the pond protected from wind and wave action. Larvae that have switched to external feeding are stocked into ponds filled no earlier than 3–5 days before stocking. Larvae intended for each pond should be of approximately the same age.

Calculation of carp broodstock stocking in spawning ponds

Task. It is required to determine the necessary number of carp broodstock in a fish farm in the Krasnodar Territory, which must produce 1,200 centners of marketable fish, based on the following data:

– yield of fry per nest of broodstock – 120,000; – yield of fingerlings from rearing ponds – 70% of stocked fry; – yield of yearlings from overwintering ponds – 75% of stocked fingerlings; – yield of two-year-olds from fattening ponds – 90% of stocked yearlings; – average weight of two-year-olds in autumn – 500 g.

I. The starting point is the set output of production:

Find the number of two-year-olds that makes up 1,200 centners of marketable produce:

1200: 0.5 kg = 240,000; 2. Find the number of yearlings that should be stocked into fattening ponds to obtain the found number of two-year-olds:

Find the number of fingerlings that should be stocked into the overwintering pond to obtain the necessary number of yearlings:

X – 100% 4. Find the number of fry that must be stocked into rearing ponds to obtain the specified number of fingerlings:

X – 100% 5. Find the number of nests required to obtain the necessary number of fry:

In one nest there is one female and two males, therefore, the main herd of carp broodstock should consist of 4 females and 8 males – a total of 12 breeders.

II For the initial basis, we take the output of one nest of carp breeders and determine:

1. output of fingerlings from nursery ponds

2. output of yearlings from overwintering ponds

3. output of two-year-olds from grow-out ponds

4. output of commercial product from one nest

According to the calculation data, the main herd of breeders should consist of 4 nests, i.e., 4 females and 8 males aged 5 to 10 years. In addition, the farm should have a reserve herd with the same number of breeders and the same age. Thus, the total number of breeders on the farm should be 8 females and 16 males.

To replenish the breeder herd, which is culled every year for various reasons (old, injured, or unsuitable by other indicators), the farm must necessarily raise replacement young fish.

The breeding instruction stipulates that 25% of the main breeder herd is replaced annually at the farm; in our calculations, this amounts to three breeders.

The replacement of culled breeders from the main herd is carried out from the reserve herd, which in turn is replenished with replacement young fish. Therefore, more replacement young fish should be raised than the number of breeders culled.

To replace one culled breeder from the herd, one must have the following amounts of replacement young fish:

At the age of five, carp are transferred to the reserve breeder herd.

The number of replacement young fish in this example will be as follows:

There are cases when it is necessary to calculate the number of breeders for a given number of hectares of nursery pond area that must be provided with already ready fry. In this situation, one can use the following formula:

P – average natural fish productivity of nursery ponds (kg/ha),

N – stocking rate taking into account feeding, в – planned average weight of fingerlings by autumn (in g), р – output of fingerlings from nursery ponds (% of fry stocking), м – output of fry per female (in thousand specimens).

Example. Determine the number of carp breeder nests with whose fry it is necessary to stock 50 ha of nursery ponds according to the following data:

– output of fry per one nest – 120 thousand.

– average weight of fingerlings by autumn – 50 g.

– output of fingerlings from nursery ponds – 70% of fry stocking.

– natural fish productivity of nursery ponds – 250 kg/ha.

Task. Determine the required number of carp breeders in a fish farm in the Krasnodar Territory, which must produce ц of commercial fish, according to the following data:

Table 1 – Pond farm indicators for determining carp breeders

1 2 3 4 5 6 7 8 9 Amount of commercial fish, ц 800 950 955 960 965 970 980 990 995 Output of fry per breeder nest, thousand specimens 90 92 94 96 98 100 102 104 106 Output of fingerlings from nursery ponds, percentage of stocked fry 65 66 67 68 69 70 70 70 71 Output of yearlings from overwintering ponds, percentage of stocked fingerlings 73 73 73 73 73 73 73 73 73 Output of two-year-olds from grow-out ponds, percentage of stocked yearlings 88 88 88 88 90 90 90 90 90 Average mass of two-year-olds in autumn, g. 480 480 485 485 485 490 490 490 490

10 11 12 13 14 15 16 17 18 Amount of commercial fish, ц 850 855 860 870 880 885 887 889 890 Output of fry per breeder nest, thousand specimens 107 108 109 110 111 115 116 117 120 Output of fingerlings from nursery ponds, percentage of stocked fry 72 72 72 73 73 73 74 74 74 Output of yearlings from overwintering ponds, percentage of stocked fingerlings 73 73 73 73 73 73 73 73 73 Output of two-year-olds from grow-out ponds, percentage of stocked yearlings 91 91 91 91 92 92 92 9 92 Average mass of two-year-olds in autumn, g. 495 495 496 496 498 499 499 500 500

19 20 21 22 23 24 25 26 27 Amount of commercial fish, ц 895 898 900 920 930 935 940 941 943 Output of fry per breeder nest, thousand specimens 110 112 114 116 118 120 122 124 126 Output of fingerlings from nursery ponds, percentage of stocked fry 72 72 72 72 72 72 72 72 72 Output of yearlings from overwintering ponds, percentage of stocked fingerlings 75 75 75 75 75 75 75 75 75

92 92 92 92 92 92 92 92 92 percentage of stocked yearlings Average mass of two-year-olds in autumn, g 505 510 515 520 525 530 540 542 545

Calculation of pond area for various categories

The amount of fish stocked into summer category ponds is determined by two indicators: achieving the desired individual weight gain by a specific date and the most complete utilization of the pond's natural food resources by the fish.

Carp growth in ponds depends on cultivation conditions and can fluctuate within a wide range. In one summer, a carp can grow to a weight of 10–30 g using only natural feed, and in the same climatic conditions up to 500–1000 g and more, if it is fed additionally with artificial feed.

Therefore, if a pond has good natural productivity, for example, 200 kg/ha or more, then more fish can be stocked per 1 ha of pond than with lower natural productivity. And if there is a possibility to supplement the fish with artificial feed, the stocking density of fish per 1 ha of pond can be increased several times over.

Thus, the stocking density of carp per unit area depends on the nutritional capacity of the pond and the individual weight gain during the growing season.

On average, the mass of fingerlings is accepted as 25–30 g, and two-year-olds as 500–550 g on the pond's natural feed. Therefore, fish stocking calculated based only on natural food is called normal, and when taking into account additional artificial feeding, it is called intensive.

Natural fish productivity largely depends on the local climatic conditions, the quality of water and soil, pond land improvement and fertilization, fish species, age, health status, and other factors.

As the stocking density increases, fish productivity rises to a certain limit, after which increasing the number of fish stocked per unit area leads to a decrease in both individual and total weight gain and may result in the deterioration of the eating quality of market fish.

When stocking fish, for example, yearlings in the spring into fattening ponds to raise them to two-year-olds, a certain portion will die. Therefore, to obtain the planned number of two-year-olds by autumn, stocking of yearlings must be higher, taking into account fish loss in the fattening ponds. On average, it is considered that fish loss during the growing season is 15–20%.

Stocking of yearlings into fattening ponds, taking into account their natural loss during the spring-summer period, can be calculated using the following formula:

B – carp mass at the end of the period (two-year-old);

b – carp mass at the beginning of the period (yearling)

Determine the quantity of yearling carp for stocking a fattening pond under the following conditions:

– natural fish productivity of the fattening pond – 220 kg/ha;

– planned mass of two-year-olds by autumn – 530 g;

– mass of yearlings at stocking – 35 g;

– yield of two-year-olds – 85% of yearling stocking.

Substituting the values of these indicators into the formula provided above, we obtain:

If it is necessary to stock fry into a nursery pond, whose individual weight at stocking is 20–50 mg, which is a very small value in relation to the final weight of fingerlings (25–30 g), it is not taken into account during stocking, and the formula is as follows:

1. Calculation of the structure and areas of ponds for carp farming

Correct calculation of the areas of ponds for various purposes allows for balancing the fish stocking density at all stages of the two-year cycle, optimizing feed costs, and obtaining the maximum volume of marketable produce. As an example, let us consider the design of a full-cycle carp farm with a total area of 400 ha with a two-year turnover.

• Fry yield from one nest — 110 thousand pcs.
• Stocking density in the spawning pond — 4 nests per 0.2 ha
• Natural productivity of nursery ponds — 270 kg/ha
• Natural productivity of fattening ponds — 230 kg/ha
• Survival rate of fingerlings in nursery ponds — 70%
• Survival rate of yearlings after overwintering — 77%

For stable reproduction, the herd is formed at a rate of 3 fish per nest (1 female and 2 males). Taking into account a 100% reserve, the main broodstock consists of 14 females and 28 males (42 individuals in total). Every year in the spring, 25% of the broodstock (5 individuals) are culled and replaced with replacement young, the final culling of which is carried out in the autumn.

After completing all culling stages, the following groups of replacement young and broodstock are left for the winter:

• two-year-olds — 20 specimens with an average weight of 1 kg (20 kg total);
• three-year-olds — 12 specimens with an average weight of 2 kg (24 kg total);
• four-year-olds — 5 specimens with an average weight of 3 kg (15 kg total);
• broodstock (from 5 to 10 years old) — 42 specimens with an average weight of 6 kg (252 kg total).

In total, 79 fish with a total mass of 311 kg are stocked into the overwintering pond for the broodstock.

To determine the exact parameters of the ponds, sequential calculations are performed according to the following scheme:

1. Calculate the yield of yearlings from 1 ha of an overwintering pond based on the fingerling stocking rate (525 thousand pcs. per 1 ha) and their survival rate (77%).
2. Determine the area of the fattening pond required for stocking with the obtained quantity of yearlings (assuming 85% two-year-old survival rate and an average weight of 550 g).
3. Calculate the required demand for fry for stocking into nursery ponds.
4. Calculate the area of spawning ponds based on the rate of 4 nests per 0.2 ha.
5. Calculate the area of nursery ponds for raising fingerlings to an average weight of 33 g.
6. Determine the area of summer broodstock ponds and ponds for replacement young based on their individual weight gain (1100 g) and fish productivity (160 kg/ha).
7. Calculate the area of the overwintering pond for broodstock and the replacement group based on a stocking rate of 320 centners/ha.

2. Standards for calculating pond areas by variants

For the design of full-cycle pond farms in the conditions of the Krasnodar Territory, the standards given in the table below are used. The data are grouped by variants depending on the total area of the farm and the planned productivity of the water bodies.