MAIN METHODS OF WARM-WATER POND FARMING IN THE U.S.S.R.

by

L.A. Erman
Candidate of Biological Sciences, VNIIPRKH

The pond fishery is one of the fastest growing branches of fisheries in the Soviet Union. According to the Five-Year Plan, the yield of fish taken in the state pond fisheries alone will be 150,000 t in 1970, five times more than in 1965. Pond fisheries can supply all year around the particularly valuable live and iced freshwater fish which enjoy great consumer demand. The fact that pond fisheries are located close to consumers also contributes to their advantages.

The Organization of pond fisheries is under the Ministry of the Fishing Industry of the U.S.S.R. and Union-Republican Ministries Fish rearing stations also belong to many collective and state farms.

Research work in the field of pond pisciculture is carried out by a number of specialized research institutes: the All-Union Research Institute of Pond Fisheries (VNIIPRKh): Ukrainian; Baltic, Byelorussian and Siberian Research Institutes of Pond Fisheries, the State Research Institute of Lake and River Fisheries (GosNIORKH) and many universities and agricultural institutes. All these institutions have their publications and articles dealing with pond pisciculture are also published in the magazines Rybovodstovo i rybolovstvo, Rydnoe Khaziaistvo, Voprosy ikhtiologii, etc.

Soviet scientists have published a number of mongraphs on pond pisciculture (Elconsky, 1946; Martyshev, 1964; Sukhoverkhov, 1963; Ilin, 1955).

The main fish in warm-water pond fisheries in the U.S.S.R. is the carp (Cyprinus carpio L.). Farms with a two-year turnover comprise the bulk of the fisheries. The first year is for rearing planting stock, i.e., fingerlings, and the second year is for growing commercial fish after the one-year fish have endured the winter.

This type of fisheries called full-cycled fisheries and has the following types of ponds:

Spawning ponds, for spawning of carp, 0.1 percent of the total production area of the fishery,

Rearing ponds, for rearing fingerlings, 5.9 percent of the area,

Wintering ponds, for the over-winter holding of carp planting stock and spawners, 0.2 percent of the area,

Fattening ponds, for rearing commercial fish, 93.8 percent of the area.

Fisheries should also have foundation ponds for keeping spawners and quarantine ponds (Martyshev, 1964).

Rearing fisheries, which only grow fish planting stock (fingerlings) or one-year-old fish) and fish fattening farms for growing commercial fish are called non-full-cycled pond farms. This kind of fishery is wide spread in collective and state farms where multipurpose ponds are usually used.

Carp ponds are characterized by the following main parameters (Mattisen, 1965).

The bottom of spawning ponds must be covered with vegetation. If there is no such vegetation, a special spawning substrate is introduced.

Rearing ponds are located in the best area close to spawning and wintering ponds. Their water supply must be independent. Some pond fisheries rear fingerlings in fattening ponds together with two-year-old fish. In this case fish productivity increases but, in view of the danger of possible epizootics, this method is allowed only in pond farms ichthyopathologically normal.

Fattening ponds are usually built by embanking a flat area of the floodlands of a small river (floodland ponds) or by partitioning its bed by a dam (riverbed ponds).

The head pond (water storage reservoir), formed by damming a small river or stream, is the source of water supply in the majority of fish farms in the U.S.S.R. Large-scale fisheries of this type use the water of larger rivers and water storage lakes.

The following main pisciculture standards are accepted in the U.S.S.R. at present (spravachnaya kniga rybovoda, 1960):

Yield of fry by one female

Yield of one-year-old fish from wintering ponds

Yield of two-year-old fish from discharging fattening ponds with an area of

Density of fingerling stock for winter period

Along with the two-year turnover farms, one-year turnover farms are also widespread in the U.S.S.R., mostly in Southern areas (Ukraine, Moldavia, north Caucasus, and the republics of middle Asia). One-year rearing is used for growing one-year-old carp weighing 250 g and over. In this case, productivity decreases but the farm does not need to roundup fish for wintering.

The development of pond fisheries in the U.S.S.R. is characterized by a rapid transition from extensive farming to intensive methods of fish rearing. In extensive farming, fish are reared only by natural food supply. In this case, the fish productivity of ponds depends on their geographical location, fertility of soil, surrounding lands and other factors.

In the main zones of pond pisciculture in the U.S.S.R., the period of a water temperature over 15°C varies from 50 to 130 days, which is considerably shorter than in such countries as Hungary, Israel and Japan.

Average natural fish productivity in the northern areas of the Russian Federation is 125 to 175 kg/ha; in northwestern republics and areas, 150 to 200 kg/ha; in the central part of the Russian Federation, 175 to 225 kg/ha; in the eastern areas of the European part of the Russian Federation, 200 to 250 kg/ha; in the central black soil zone, 225 to 275 kg/ha, and in the southern areas of the Russian Federation, 300 to 350 kg/ha (Martyshev, 1964).

In the forest-steppe region, in the Ukraine, due to natural fish productivity, it is possible to obtain an average of 320 kg/ha of carp; in the steppe zone, 400 kg/ha, and in the wooded district, 150 kg/ha (Shpet, 1962). Extensive methods of fish farming are used mostly by collective and state farms where fish rearing is not the main occupation.

The intensive method of carp rearing prevails in all specialized fisheries stations and many collective and state farms. The gist of this method is the regular application of feeding, fertilization and melioration of ponds, multispecies farming and other measures. All-round intensification makes it possible to increase fish productivity many times and to raise the economic efficiency of pisciculture.

Fish productivity of ponds with intensive farming depends both on soil and climate conditions and on the level of production standards in individual areas and fisheries. The experience of advanced fisheries is significant in this respect. At present, the bulk of pond-reared fish is grown in central non-chernozem zone, central black soil zone of the Russian Federation, in the north Caucasus, in the Ukraine and Byelorussia, because the majority of fish rearing farms with good production histories are situated mostly in these regions.

The fish productivity of fattening ponds in the advanced fisheries of these regions averages 1.5 t/ha and that of rearing ponds, 1.6 to 2.0 t/ha. The following table shows some economic indices of such farms from 1963 to 1965.

* Multispecies farming of carp, together with some herbivorous fish.

Pond fisheries in the Ukraine are very efficient and provide about 50 percent of the total fish taken in the inland water basins. Fattening ponds of many of the best farms in the Ukraine yield 1.0 to 1.2 t/ha of carp and some of them even 3.2 t/ha (Shpet, 1962).

One-year farming gives good results in the Ukraine, Moldavia and the Caucasus. In the south Ukraine commercial size yearlings gain 500 to 600 g in weight, fish productivity being 0.4 to 0.8 t/ha (Grinevich, 1965). Even better results have been achieved by this method in Moldavia. With feeding, productivity here amounts to 1.1 to 1.3 t/ha, while natural fish productivity is 0.6 to 1.1 t/ha (Poyag, 1965). Similar figures have been obtained on the Kuban River in the north Caucasus. There one-year farming without the application of feeding has secured 0.36 to 0.50 t/ha and with the application of feeding, 1.15 to 1.33 t/ha. (Strelnikov, 1964). In Georgia fish productivity of yearlings has equalled 2.0 to 2.3 t/ha (Peskova, 1962).

Very favorable conditions for pond pisciculture exist in the republics of central Asia. However, not all reserves have been utilized here so far. In south Kazkhstan the fish productivity of fattening ponds does not exceed 1.32 t/ha and that of rearing ponds, 1.68 t/ha.

The experiment in obtaining two yields of fish during one year in Uzbekistan deserves special attention (Puchayev, 1965). Carp fry were released in May-June in a fattening pond stocked with one-year-old fish discharged in spring. Two-year-old fish were caught in August and commercial size fingerlings in October, gross productivity in this case amounting to 3.62 t/ha.

In recent years pond fisheries have begun to develop in Siberia, the Urals and norther Kazakhstan. Average fish productivity of fattening ponds in the Urals has amounted to 0.56 to 0.70 t/ha, in the Novosibirsk and Kemerovo regions, 0.75 t/ha, with the maximum of 1.73 t/ha (Petkevich et al., 1965).

In the northern and northwestern parts of the European part of the U.S.S.R. conditions for pond farming are less favorable. Nevertheless, in Byelorussia advanced fish rearing farms obtain 0.8 to 1.1 t/ha of commercial carp.

High fish productivity is achieved in progressive fish rearing farms by means of all-round intensification. Some problems of intensification and biotechniques of pond pisciculture (the fertilization of ponds, selection and breeding, epidemic control, trout farming, new methods of obtaining progeny of pond fish) will be given special attention at this seminar and we shall not dwell upon them here.

One of the main elements of intensification is the feeding of fish with artificial concentrated fodder which, together with dense planting, is the main means of raising fish productivity. Many fisheries of the U.S.S.R. apply the method of 5 to 10-fold stocking of carp (2,000 to 5,000 one-year-old spec/ha as compared with natural fish productivity). In this case 80 to 90 percent of the increase in the amount of fish is secured by artificial fodder.

By spending less energy on the main metabolism, the carp use the fodder for gaining weight more effectively than warm-blooded agricultural animals (Polyakov, 1951).

Rearing fish in dense stocking conditions entails the supply of all their main nutrients from artificial fodder. Consequently, this fodder will be effective only if it is nutritionally balanced in accordance with the need of the fish. Mixed fish fodder should contain, for instance, the necessary amount of protein. The ratio of protein, i.e., the relation of assimilative protein to non-nitrogen assimilative substances, for fingerlings should average 1 to 2 and for two-year-old fish, 1 to 5.

It is now known that protein does not guarantee the balance of fodder in respect to indispensible amino-acids. All-vegetable fodders are poor in lysin and metionin, so it is necessary to add some products of animal origin, e.g., fishmeal, or hydrolysed yeast, rich in these amino-acids.

The fodder should contain the complex of vitamins necessary for fish. The addition to the diet of carotene (provitamin A) in the form of paste made from milled green vegetation or grassmeal powdered after special drying, is of great importance.

The addition of 30 percent green paste to the diet of the two-year-old carp has considerably increased its productivity. The content of carotene in the liver of underyearlings which get this addition to their diet has increased and their ability to endure the winter period has been improved (Deyeva, 1964).

The group B vitamin content in the fodder is of great importance for fish. Hydrolyzed yeast can be used as a source of these vitamins. The addition of yeast at the rate of four percent of the diet has resulted in an increase in productivity of 16 percent in experiments carried out by VNIIPRKH.

Formulas for the concentrated fodder recommended by VNIIPRKH are given in the following table (Sukhoverkhov, 1963).

The fodder coefficient for two-year-old fish in the diet is recommended to be about 4.5. Along with special fodder mixtures, the wastage of food production, especially those of flour-milling and grain-peeling are also widely used. It is recommended to add 20 percent greenpaste and 10 percent slaughtering wastage to the flour-milling wastage (Chizhov, 1964).

The growth of carp can be stimulated and the consumption of artificial fodder can be increased by adding some stimulants in form of microelements and antibiotics. Cobalt has proved to be the most effective of all microelements. It is known that this element is included in vitamin B₁₂, which is very important for blood-formation and the synthesis of muscular proteins. Even in the central black-soil zone conditions where the soil is rich in cobalt, a daily addition of 0.02 to 0.08 mg of cobalt per kg of the weight to the diet of two-year-old carp has resulted in an increase in weight and fish productivity and fodder expenses were cut by 20 percent (Sukhoverkhov, et al., 1963). The introduction of cobalt into the diet of carp fingerlings has made it possible to increase their productivity by 11.5 percent, the fodder coefficient being lowered by 8.5 percent (Vinogradov, Erohina, 1962).

Both fingerlings and two-year-old carp which had cobalt added to their diet were marked by an increased number of erythrocytes and content of hemoglobin in the blood and for a decrease in the total of leucocytes. It has been proved that the introduction of cobalt is effective only in the case of high quality fodder. Some pisciculturists use a complex of microelements (cobalt, manganese, copper, zinc) when feeding the carp. In the Gorky region, the introduction of this complex into the diet has allowed fodder expenses for growing two-year-old carp and fingerlings to be considerably decreased (Khuznetsov, Remez, 1964). In the Latvian SSR the application of a complex of microelements and antibiotics has resulted in an increase in the yield of carp by 50 percent (Pricdites, 1963). Under experimental conditions, a positive result has also been obtained by adding molybdenum and manganese to the fodder (Karamzin, 1964).

The fodder antibiotic terramycin, used as a biostimulant has given a substantially positive effect. The best result has been achieved by introducing terramycin at the rate of 20,000 units per kg of fodder every four days. The fodder coefficient in this case has been lowered by 14 to 17 percent (Korneyeva, 1965). The application of terramycin in the experimental ponds of the Kuybyshev region has resulted in an increase in weight and a decrease in fodder expenses. During the working condition test in the Moscow region, the fodder coefficient was reduced, due to the application of terramycin, by an average of 10.5 percent and fish productivity increased by 12.5 percent.

The U.S.S.R. has also achieved positive results in application of penicillin as a biostimulant (30 mg per kg fodder for fingerlings). Fish productivity in this case has increased by 11 to 23 percent (Karpanin, Ushakov, 1961).

The effectiveness of the above additions to the fodder depends on a number of factors and must be rated for each individual case.

The reduction in the cost of concentrated fodder per unit increase of fish can be achieved, not only by improving fodder quality, but by more efficient feeding as well. VNIIPRKH investigations have shown that fodder given to fish in the form of heavy dough, as is done in the majority of fisheries in the U.S.S.R., quickly dissolves and washes away. In this case 30 percent of the nutrients contained in it are lost. To prevent these losses, the fodder should be given to fish in the form of granules prepared by wet pressing. Granules prepared by dry pressing get sodden quickly and their use reduces losses mostly during transportation and in the expenditure of labor during the feeding. In experiments carried out by VNIIPRKh, the use of granulated fodder prepared by wet pressing has allowed the fodder coefficient in rearing commercial carp to be decreased by 26.7 percent, as compared with the loose fodder coefficient, i.e., to be brought to 2.2 (Erohina, 1959).

The equipment needed for the production of granulated fish fodder is now being designed.

One of the most effective methods of raising fish productivity of ponds is the introduction of multi-species farming, including species which so far have not been objects of pond fish breeding.

The following three goals should be sought in this case:

1. Fuller utilization of natural food resources of ponds, especially of food resources rarely used by carp (phytoplankton, detritus, macrophytes, microzooplankton);

2. Selection of species more adaptable to the conditions of a special area. (Not all areas of the vast territory of the U.S.S.R. have favorable conditions for carp farming, northern areas for instance);

3. Expansion of the variety of fish products by using more valuable fish (e.g., sturgeon, salmon).

The acclimatization of herbivorous fish of the far eastern faunistic complex, i.e., white amur (Ctenopharyngodon idellus Val.), silver carp (Hypophthalmichthys molitrix Val.) and bighead (Aristichthys nobilis Richards), has been carried out on a large scale in recent years in the European and central parts of the U.S.S.R.

White amur feeds on high aquatic vegetation (macrophytes). The rearing of white amur in ponds results, not only in additional increase in fish production, but also produces a substantial meliorative effect. White amur devour thickets of macrophytes and so prevents the overgrowing and bogging of ponds. Silver carp feed on phytoplankton and detritus. Big-head food is mostly small forms of zooplankton, big planktonts and detritus. Thus these fish do not use the carp food.

The far eastern fish have been brought to Central Asia, the north Caucasus and the Ukraine. At present they are mature and reproduce regularly.

The new method worked out in the U.S.S.R. for obtaining larvae of these fishes is dealt with at this seminar in a special lecture. We shall only dwell on methods and effectiveness of rearing vegetable-eating fish in ponds.

The larvae of amur, silver carp and bighead obtained in the southern areas of the U.S.S.R. are transported in polyethylene bags inflated with oxygen. At present hebivorous fish are brought in this way to all pond farming areas and to scores of fisheries in various zones. The wastage of larvae which have just begun active feeding should not exceed five percent if transportation does not last longer than 30 hours.

The larvae are released into nursery ponds, where they are reared together with carp. The density of the stock should be 30,000 to 100,000 spec/ha. The yield of fingerlings is usually not less than 50 percent of the fry stock (Vinogradov, 1965). Fish productivity of herbivorous fishes in nursery ponds can be very high in southern fisheries. Under favorable conditions fingerlings gain an average of 50 to 100 g in weight. In the Sinuhinsky fishery farm in the Krasnodar territory in 1965, the yield of amur, silver carp and bighead fingerlings was 1.76 t/ha of the rearing ponds and in the Angelinsky fish hatchery it was 1.75 t/ha. Fish production of white amur and silver carp in the Moscow region was 0.5 t/ha. The growth and survival rate of silver carp and bighead reared together in conditions of increased density of carp did not lower but, on the contrary, increased.

The young herbivorous fish easily endure the winter period. The yield of one-year-old fish is 80 percent. The survival of two-year-old herbivorous fish reared in fattening ponds together with carp is also high, amounting to 90 percent.

VNIIPRKh investigations show that stocking carp ponds with any of the three species of herbivorous fish at the rate of 1,500 to 2,000 two- or three-year-old fish per ha, does not reduce the growth rate of carp and allows the fish productivity of the fattening ponds to be considerably increased. In the central black soil zone (Kursk region) two-year-old herbivorous fish species have averaged 0.45 t additional commodity output per ha and three-year-old fish, 0.65 t (Ilin, et al., 1965). In the non-black soil zone (Moscow region) the planting of white amur has mostly resulted in 1.30 t of marketable fish per ha, with gross fish productivity being 2.54 t/ha (Bobrova, 1965). When the white amur were fed with mowed grass the fodder coefficient equalled 12.0 to 15.5.

Multi-species farming of herbivorous fish with carp has proved most effective in the fisheries of the northern Caucasus. In 1965 in the Sinuhinsky fishery, for instance, due only to addition of bighead, the yield of commodity fish varied from 0.67 to 1.74 t/ha, the weight of a specimen averaging 1.926 g. In the Kurchansky lagoon farm amur, silver carp and bighead accounted for 0.53 to 0.84 t/ha of additional production and in the Angelinsky fishery, 1.08 t/ha. Similar results were also obtained in 1964.

In Moldavia the multi-species farming of herbivorous fish with carp has increased gross fish productivity to 1.92 to 3.40 t/ha.

Practical experience has shown that by farming herbivorous fish in the central belt of the R.S.F.S.R., it is possible to increase the fish productivity of fattening ponds by an average of 0.3 to 0.5 t/ha and in the south of the European part of the R.S.F.S.R. by 0.6 to 1.0 t/ha.

In the northern and northwestern areas of the European part of the U.S.S.R., where rearing far eastern herbivorous fish is as effective as in the south, peled-a-cisco (Coregonus peled Gmelin) and other Coregonus should become the principal additional fish reared with carp. Peled-a-cisco lives in Siberian rivers, feeds on zooplankton and is able to adapt to different environments. It can endure short-term rises of temperature up to 26 to 28°C and a decrease of dissolved oxygen in the water to 4 mg/l. Due to this it has become possible to acclimatize it in fish farms, not only in the north and northwest but in the central black soil zone of the R.S.F.S.R. and the Ukraine as well (Golikov, Kuzmin, 1963).

In the North peled-a-cisco fingerlings gain from 16 to 118 g in weight and two-year-old fish from 100 to 550 g. Rearing commodity peled-a-ciscu fingerlings is most effective in the central zone and in the Ukraine where fish productivity of ponds occasionally increased by 130 kg/ha.

Polyakov cisco (Coregonus lavoretus marenoides) is also reared along with peled-a-cisco, both in northern and southern areas of the U.S.S.R. This benthos-eating fish is remarkable for its quick growth (fingerlings weight 20 to 70 g and two-year-old fish, 400 g) and guarantees high fish productivity of ponds (150 to 200 kg/ha) under favorable conditions.

As for plankton-eating Coregonus, northern and northwestern fish farms are successful in rearing vendace (Coregonus albula Linne) and “ripus” (Coregonus albula morpha vimba Linne).

Crucian carp (Carassius auratus gibelio Bloch) is also used as an additional fish in a number of fish farms in various regions of the U.S.S.R. This fish grows more slowly than carp but surpasses it in palatability and a better use of zooplankton. Two-year-old crucian carp average 180 g and thr three-year-olds average 400 g. As a rule, by farming crucian carp, fish farms raise fish productivity of fattening ponds by 25 to 30 kg/ha. VNIIPRKh experiments have shown that rearing the unisexual form of crucian carp is more expedient as this form is remarkable for its quick growth and later maturity (Cherfas, 1965). Releasing crucian carp into carp ponds has allowed natural fish productivity to be considerably increased.

It is expedient to release predatory fish into fattening ponds where a great number of small wild fish can easily penetrate, since they eat the scrap fish competing with carp in feeding.

Pike (Esox lucius L.) and pike perch (Stizostedion lucioperca L.) are used for this purpose in the U.S.S.R. Interesting experiments are being conducted in rearing pike perch. The spawning of pike perch can be easily carried out in floating stews with artificial nests made from kapron bristle (Miheyev, Meysner, 1960). Pike perch fingerlings gain 20 to 60 g in weight in ponds of the central zone of the Russian Federation, two-year-old specimens gain 300 to 500 g and fish productivity is 15 to 20 kg/ha. In the Ukraine it is possible to obtain commodity pike perch fingerlings weighing 200 to 300 g (Nikoluk, 1965).

In recent years experiments have been carried out in the U.S.S.R. on the effect of pond farming of sturgeon (Acipenseridae), which possess particularly palatable properties. Rearing hybrids of white sturgeon (Huso huso) and sterlet (Acipenser ruthenus) is very promising.

Hybrids feed on benthos and scrap fish in ponds. They can also be fed with small fish forcemeat. In two years hybrids gain up to 400 to 500 g in weight (Nickolukin, Timofeyeva, 1956). In conditions of multi-species farming, the fish productivity of sturgeon fattening ponds can amount to 200 to 250 kg/ha.

Some fish farms in the U.S.S.R. rear ducks in carp ponds. Ducks feed on aquatic vegetation and tough fauna harmful to fish (Coleoptera, Odonata, Hemiptera), devour notostraca (Apus) and tadpoles. At the same time they hoe the bottom of the pond and thus play the part of good meliorators. Droppings of the ducks serve as fertilizer. Keeping ducks on the fattening ponds results in an increase of natural fish productivity by 20 to 25 percent. In view of the danger of surplus accumulation of organic substances in the ponds and diseases and death of fish, the density of the stocking of ducks should not be too high. It should not exceed 100 to 200 spec/ha. (Letichevsky, 1963).

One important means of reducing production costs of pond fish is by cutting labor expended on their rearing by mechanization of pisciculture labor.

Special machinery is now being built for manufacturing fodder, applying fertilizers, cutting aquatic vegetation etc. Many fish farms have mechanized these operations by using equipment turned out by Soviet industry for agricultural purposes. Dough-like fodder is kneaded with the help of special fodder mixers equipped with a fodder dosing bunker and conveyor. To prepare green vegetable paste IKB-I feedmills are used (Grib, 1964). Many fish farms, for instance Beloye and Volma in Byelorussia, have mechanized the operations dealing with catching, sorting, antiparasitic processing and loading fish.

One of the most important sources of pond pisciculture in the U.S.S.R. is the digging of ponds on lands now useless for agriculture and the use of existing multipurpose reservoirs.

VNIIPRKh has worked out methods of designing, building and operating full-cycle fish farms on peat bogs. In the U.S.S.R. there are more than 230,000 ha of exhausted peat pits where peat was extracted by the milling method (millpeat) and by pumping (hydropeat).

These lands, especially hydropeat pits, are of little use to agriculture. Facilities used during peat extraction, i.e., water storage reservoirs, canals, roads, settlements etc. are employed for fish farm schemes. This allows the capital expenditures for building fish farms to be considerably reduced (Brudastova, 1962).

To increase fish productivity of poor peat ponds a complex of intensifying measures is used which includes applying lime (0.7 to 1.0 t/ha), organic fertilizers (0.1 to 0.3 t/ha), ammonium nitrate (0.2 to 0.5 t/ha), superphosphate (0.15 to 0.20 t/ha), potassium salt (0.05 t/ha) and the method of feeding fish. This results in deoxidation of the soil of ponds and accumulation of fertile silt. Due to these measures, the fish productivity of fattening ponds on hydropeat lands in the Moscow region has increased up to 1.26 t/ha and on milling fields up to 0.14 t/ha. Some methods of treating carp during the spawning period, rearing fingerlings and securing their winter stay at peat pits have been worked out. Due to all-round organomineral fertilization, the fish productivity of rearing ponds on peat lands has averaged 0.5 to 0.6 t/ha. The application of peat-ammoniac fertilizers (TAU) prepared on the spot and introduced into peat ponds has proved to be very effective. Due to the mobilization of peat biogenic elements, it has become possible to reduce the expenditure of nitric fertilizers 2 to 3 times and phosphoric fertilizers 1.5 to 2.0 times and productivity of fattening and rearing ponds has increased by 80 to 100 kg/ha (Mints, Khairulina, 1965).

Rearing pond fish in checks in rice fields is especially promising in the southern regions and republics of the U.S.S.R. There is no need to dig special ponds under these conditions. Carp placed in checks meliorate the soil and devour pests and seeds of weeds. Experiments in rearing carp in combination with growing rice have resulted in a 0.25 to 0.60 t/ha increase in rice productivity. Fish productivity is not usually high, i.e., 0.10 to 0.15 t/ha (Kamilov, 1965). A considerably higher fish productivity can be obtained by rearing fish in flooded fallow rice checks. Productivity of two-year-old carp reared in rice checks in the Karakalpak SSR has risen up to 0.8 to 1.1 t/ha, the average productivity being 0.63 t/ha (Sultanmuratov, 1965). According to data obtained by VNIIPRKh the multi-species rearing of herbivorous fish together with carp has allowed fish productivity to rise up to 1.22 t/ha.

Stocking of fallow rice checks with white amur at the rate of 200 spec/ha has resulted in complete extermination of weeds.

VNIIPRKh has worked out methods of employing the vast shallow waters and natural food resources of large water storage lakes for rearing pond fish. The shallows of water storage lakes are regularly flooded and become dry again when the water level of the reservoir drops. These lands cannot be used for agriculture, but they can be used for setting up full-cycle fish farms if they are separated from the rest of the reservoir by dams. Then the fluctuation of the water level of the reservoir is used for filling the ponds. Sometimes pumps are used for this purpose. The Suskanskoye fish rearing farm based on this scheme on the Kuybyshev water storage lake, is now under construction. It will cover 7,100 ha and will yield annually 8,800 t of commercial fish (twice as much as the yield of the reservoir) and 3,000,000 fingerlings of valuable species to be released into the reservoir (Miheyev, Meisher, 1965).

All the reservoirs of the European part of the U.S.S.R. abound in worthless scrap fish, molluscs, crayfish and aquatic vegetation. Research has been done on the use of these resources for feeding pond and river fish of valuable species, placed in floating kaprin stews. The size of the stews designed by VNIIPRKh are 36 m² (Miheyev, Meisner, 1962). Due to water circulation the conditions in the stews are the same as those of the reservoir in which they are set. Stews are used for rearing carp, crucian, hybrids of sturgeon, rainbow trout (salmo gairdnerii) and sheatfish (Silurus glanis L.). In this case live feed for fish is procured in the reservoir with plankton crayfish obtained by using the electric light attraction method. Rearing with the use of stews is especially effective in raising rainbow trout which are fed on mince made of scrap fish and molluscs. Rearing rainbow trout by this method has allowed fish productivity to rise to 7.8 kg of commercial fish per m², fodder coefficient being 3.4.

The research carried out by the Ukrainian Research Institute of Pond Fisheries has proved that return water reservoirs of sugar refineries can be successfully used for rearing commercial carp (Yarovenko, et al., 1965).

The use of the cooling reservoirs of thermal stations for pond pisciculture purposes is extremely promising. Higher water temperature in these reservoirs provides especially favorable conditions for such thermophilic fish as carp and herbivorous fishes of the Far East.

VNIIPRKh has carried out experiments for the purpose of using thermal reservoirs for rearing carp in floating net stews. It has been proved that, under a temperature of 25 to 29°C, it is possible to obtain 60 to 100 kg of commercial carp per m² of the stew, the fodder coefficient being 5.2 to 5.6. A nourishing diet, balanced in amino acid composition and vitamin content, is the key to carp effectively feeding on artificial fodder in thermal stews (Korneyeva, 1965).

The use of thermal reservoirs for rearing herbivorous fish especially white amur used as a meliorator, has also proved to be very effective (Verigin, 1961). With the help of white amur it has become possible to clear water bodies of thickets of macrophytes.

Working out methods of reproduction and intensive feeding of pond fish in stews and water bodies by using thermal reservoirs, will allow pond fisheries to go over to advanced rearing of fish by the stall method.

This lecture has outlined the experience of the advanced fisheries of the U.S.S.R. and the achievements of a number of research institutions in this field, the achievements of VNIIPRKh in particular.

In conclusion, let us dwell on the main tasks and prospects in the development of pond pisciculture which generally determine the scope of research in this field.

Increase in production of pond fish in the U.S.S.R. should be gained, according to the Five-Year Plan, by both building new fish farms and by raising productivity of existing ponds. High profitability of pond fisheries should be obtained along with this. The high profitability, of course, depends on the cost of production and the amount of capital expenditure.

The production cost of pond fish is composed mostly of the cost of fodder, fertilizers, planting material and labor. The production cost can be reduced by improving biotechniques of fish breeding and rearing.

The main task in fish feeding is to cut the cost of concentrated fodder. To do this, it is necessary first to study the need of fish for main nutrients (proteins, some amino acids, carbohydrates, fats, vitamins, main mineral elements and microelements). It is also necessary to know digestibility and assimilability of the nutrients of different fodders by fish. Research in this field should serve as a theoretical basis for making up nourishing fodder diets that meet the needs of fish. It is also necessary to continue investigations in the application of various growth biostimulants to fish feeding and to make use of the experience of other branches of stock breeding.

Improving the preparation of fodder for feeding-up (granulating, etc.) should also contribute to reductions in fodder expenses. By all-round application of all these methods we hope to considerably decrease the fodder expense per gain unit of carp.

As has been shown above, a sharp increase in fish productivity can be gained by introducing multi-species farming of fish and fully utilizing natural food resources of ponds. Stocking carp ponds with herbivorous and plankton eating fish also allows the expense of concentrated fodder per production unit to be considerably reduced, as these fish gain weight by feeding mostly on natural food which carp do not use. Improving the biotechniques of obtaining the progeny of these fish, transportation of the young and food interrelations between these fish and carp at different stages of development are the main problems in this field. Other problems are the intensiveness of their feeding and food selectivity as a theoretical basis for determining pisciculture standards (density of stocking, correlation of individual species, etc.). Introduction of new species into fish farming is regarded as expedient.

It should be mentioned that in the U.S.S.R., where climate conditions are greatly varied, economical biotechniques of pond pisciculture should be worked out in view of their application in specific zones. Utilization of the experience of Soviet pisciculture in foreign countries also should be viewed from this standpoint. Such indices as the period of rearing (1, 2 or 3 years), commodity weight, and natural fish productivity of ponds depend first of all on climate conditions.

Complex theoretical problems face pond pisciculture in connection with working out methods of fish rearing in stews (stall system rearing). The artificial fodder used in this case should be very thoroughly balanced in nutrients as the fish are practically deprived of the possibility (in industrial thermal reservoirs at least) of obtaining missing components from natural food. Correct rating of the density of stocking, the method and regime of feeding as determined by the behavior of fish and their metabolism, are of great importance in this case.

Physiology and behavior of fish, in particular, are closely connected with mechanization and automation of fish farming operations. Specific reaction of fish is taken into consideration in working out methods of catching fish in ponds (catching with the use of electric light, for instance). Under conditions of automation in feeding fish and control of regime of water bodies, it is necessary to secure control and registration of physico-chemical environmental conditions, eating of fodder by fish etc.

Reduction of capital expenditure on building fish farms is another source of raising the profitability of pond pisciculture. This can be achieved first of all by maximum use of existing water bodies, i.e., peat pits, rice checks, water storage lakes and industrial reservoirs. To solve this problem, it is necessary first of all to thoroughly study the regime of such reservoirs and to work out methods of control in the interests of pond fisheries. This, as a rule, brings about a number of specific biotechnical problems.

The use of peat ponds for pisciculture purposes, for instance, involves such problems as deoxidization of the soil of ponds and making the biogenic elements of peat more active. When stocking fallow rice checks with fish, it is necessary to work out the standards of stocking with different species which would secure both pisciculture and meliorative effects.

To utilize natural food resources of water bodies, it is necessary to work out methods of collecting the organisms which can be used as food for fish. All-round utilization of water bodies is especially effective in combination with intensive methods of fish rearing.

Working out the theoretical basis and methods of pond pisciculture, introduction of multi-species farming, intensification, improvement of biotechniques and all-round utilization of water reservoirs are the main means of raising the effectiveness of pond pisciculture.

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