A.S. Zonova and V.S. Kirpichnikov
Scientific Research Institute of Lake and River Fisheries
The main object of selection of hybrids of cultivated carp and wild carp was the development of a new breed (for northwest U.S.S.R. and Siberia) that would combine in itself the best properties of the parent forms. Attempts were made to induce such characters as cold and winter resistance and high quality fish meat, retaining the ability of the cultivated carp to grow quickly in ponds and also be highly productive in breeding.
The choice of the kind of cultivated carp for crossing purposes presented no difficulty. When the work was initiated (in the forties) there were only the Ukrainian carps selected by A.I.Kuzema and the non-selected mixed carps available in the U.S.S.R. The latter was chosen, as the use of heat resistant, selected Ukrainian carp offered little prospects. Scattered mirror carp were selected from the available Ukrainian scaled carp. Scaled carp were omitted because of the possibility that they were tainted with hereditary characters of the wild carp. Linear and leather carps could not be chosen because they bear the lethal gene N and possess poor reproductive capacity.
It was more difficult to choose a race of wild carp. Extensive comparative studies of different geographical varieties of wild carp were required to evaluate their qualities, in particular, to determine their hereditary characteristics such as growth rate, cold-resistance, winter-hardiness and other relevant characteristics.
The most important results of exhaustive studies on experimental taxonomy of wild carp were published by Kirpichnikov (1943, 1949, 1967, a,b). As a result of these studies, the advantages of the Amur wild carp (C.carpio haematopterus) in respect to growth rate, rate of metabolism and activity in feeding became known. Its remarkable winter-hardiness, however, played a decisive role in its selection. Fingerlings of the Amur wild carp could survive winter well in the ponds of northwestern regions of the U.S.S.R. (Kirpichnikov, 1941, 1944, 1949; and Kirpichnikov et al., 1955). This winter hardiness can be explained by the climatic peculiarities of the river Amur - winter is long and severe and ice may be one metre or more thick; hence, the fish inhabiting the Amur river were adapted to long hibernation at very low temperatures (Kirpichnikov, et al., 1958.
Thus, non-selected scattered (scattered refers to scale pattern) carp from collective fisheries of the middle region of the U.S.S.R., as well as the Amur wild carp were chosen for initial crossing. Scattered carp have genotype ssnn; therefore, hybrids appeared to be heterozygous for genes S and s (Ssnn). This was the vital reason for a total check of hybrid broodstock for homozygosity according to gene S (scaled). It was worthwhile to select more resistant scaled carp for the severe northern zone of the U.S.S.R.
The Amur wild carp was brought to the Northwest in 1939–1941. The hybrids of the Amur wild carp were first bred there in 1946. The work on hybrid selection started in 1949 when the advantages of the Amur wild carp became evident as compared to other subspecies and races. In that year, hybrids of the second generation were obtained, followed in successive years by the third, fourth, and fifth generations. At first all the work was carried out in the fish farms of the Novgorod region. Since 1953 the work has been transferred to the experimental pond-fishery Ropsha (Leningrad district).
Hybrids of the second generation were grown in the fishery of Yazhelbitsy, Novgorod district, during 1949–1951. They were available as a result of crossings of scaled hybrids of the first generation brought from the Gorky district. Among the offspring there was segregation into scaled and scattered hybrids in the ratio of 3:1; out of 91 000 fingerlings, 68 800 (75.6 percent) were scaled, while the remainder (24.4 percent) were scattered. In autumn, the scattered fishes weighed 5–10 percent less than the scaled ones, and they did not survive winter well. This was another evidence of the necessity for further work with scaled hybrids only.
Hybrids of the third generation were first obtained in 1952. To increase winter hardiness (which proved to be inadequate in the hybrids of the second generation) two heterozygous crossings were performed. Scaled hybrids of the second generation were back crossed with Amur wild carp, as well as with hybrids brought from the Vursk district. The first crossing gave rise to the strain R (reversive hybrids), the second one to the strain I (interlinear hybrids). The Vursk hybrids used for the last crossing resulted from mass, uncontrolled crossings of the Amur wild carp with selected carp and with the hybrids of the first generation, which possessed a large share of inheritance of the characteristics of the Amur wild carp (probably about 75 percent).
Reversive hybrids were scaled as expected:
|scaled (hybrids of the 2nd generation)||scaled||(hybrids of the 3rd generation ‘B’)|
The study of reversive hybrids revealed a high viability and good growth rate in the first year of life, but there was a marked decline in growth during the second and particularly in the third year of life. The hybrids had wider and deeper bodies and were distinguished by increased winter-hardiness.
Among interlinear hybrids of the third generation, a segregation according to their scale characters was observed:
|(Novgorod hybrids of the second generation)||(Kursk scaled hybrids of the second generation||Scaled||Scaled||Scattered|
|(hybrids of the third generation)|
The number of scattered fry depended on the genotype of Novgorod hybrids. When only heterozygous spawners were used, there was about 25 percent scattered hybrids among the offspring, while the number decreased to 12–18 percent when the spawners were mixed.
Interlinear hybrids of the third generation were characterized by high viability and rapid growth during the first and the second years. At the same time, these hybrids, when judged according to body shape, could be placed as intermediate between the selected carp and the wild carp, but they were inferior to reversive hybrids when tested for winter-hardiness. In respect to growth and viability, interlinear hybrids of this generation possessed a distinct and rather significant heterosis (Kirpichnikov, 1959, 1960a).
Hybrids of the fourth generation were first obtained in 1959. Apart from reproduction of strains R and I, a new intermediate strain IR was bred as a result of reciprocal crossings of reversive and interlinear hybrids. In strain I, a distinct inbred depression was observed; while in less inbred strains IR and R, no signs of depression were detected. No segregation as to scales was observed in many crossings after specially selected spawners had been tested for homozygosity according to gene S.
The hybrids of the fifth generation (1964–1967) belong to the same strains. Mass crossings were used to decrease inbreeding. Females and males, as a rule, belonged to different families, and were chosen from the spawners tested for homozygosity according to gene S.
In 1964, selection of Ropsha carp was started with reference to resistance to infectious dropsy. The work was carried out in the fishery of Angelinka in the Krasnodar territory where there was high incidence of dropsy. In 1966–1967, they obtained hybrids of the sixth generation which had undergone selection for resistance to dropsy (Kirpichnikov, et.al., 1967).
Ropsha carp hybrids (third generation) were brought to the Ukraine in 1954. At present they have the fifth and the sixth generation of hybrids there, and these are being crossed with the local Ukrainian carp (Kuzema and Tomilenko, 1962).
Ropsha hybrid carps bred in the Northwest, in Krasnodar territory and in the Ukraine, and lately brought to Estonia and west Siberia as well, belong to three strains (I, IR and R). They differ from each other in the share of the Amur wild carp inheritance - from 60 percent (in counts) among the carp of I strain and up to 75 percent among the carps of R strain. All three strains are bred separately, but they are close to each other genetically as can be seen from the diagram of their pedigree (Fig.1).
The following methods for improvement were applied in the process of Ropsha carp selection.
2.2.1 Mass selection
Selection was started while hybrids of the second generation were being bred and was continued in all successive generations. The chief criterion for selection was the weight of fingerlings and of two-year-olds. Table I presents the severity and intensity of selection among Ropsha carp.
Severity and Intensity of Selection for Weight among Ropsha Carp
|Number of crossings||Severity of Selection in Percent|
Intensity of selection, i (inσ)
Fig.1 Pedigree of Ropsha carp. CC - cultured (Galician) mirror carp; AWC - Amur wild carp; HN and HK - hybrid carps of Novgorod and Kursk strains; HR, HI and HIR - hybrids of three selected strains (reversive, interlinear and intermediate). In double frames - heterosis combinations (HC).
It is clear (from Table I) that selection was not very severe in the second generation. In the third generation the emphasis was placed on fingerling selection. After a special test, the method of selection was altered because of the low correlation between the growth of fish in the first and second years of life; hence, partial culling of future champions occurred when strict selection of one-summer-old fingerlings was conducted. Within the fourth and particularly the fifth generation, the selection among the fish of the first and the second year of life was done more or less evenly. From 10–20 percent of the fingerling fish was left and grown for breeding, and approximately the same percent was taken from the two-year-olds. The total severity coefficient of selection during two years amounted to about 1–2 percent.
At the time of selection, the fingerlings weighed 20–50 g, whereas the weight of two-year-olds reached 160 g. Taking into consideration low heritability of weight differences, the effect of selection, however, could not be greater. On the whole, selection resulted in fish that grew more rapidly, as will be seen later.
In the course of selection, other characters were considered, the exterior features in particular.
In the Krasnodar territory selection was carried out mainly in respect to dropsy resistance. All the experiments were made in conditions of severe dropsy outbreaks when the symptoms of the disease were observed among most of the growing fish. Only those fish which did not catch dropsy under the same conditions were left for further breeding. In 1967, offsprings were produced from the fish that had undergone such selection. In the near future it will be necessary to check the efficiency of the previous Ropsha carp selection for resistance to infectious dropsy.
2.2.2 Checking of spawners for heterozygosis
More than 400 males and females were checked by crossings with scattered or heterozygous scaled spawners in the third and fourth generations.
The larvae that hatched as a result of artificial fertilization of spawn were grown in aquaria until the period of scale formation. This check made it possible to detect homozygous spawners (Table II) and make use of them for obtaining homozygous (according to gene S) offspring.
Check of Ropsha carp spawners for heterozygosis according to gene S
|Generation and strain||Years of check||Number of checked spawners|
|Homozygote number||Percent||Heterozygote number||Total number|
2.2.3 Progeny testing
This type of selection was not of practical importance in this work. It was mainly aimed at evaluation of methods. However, certain specimens checked according to offspring, especially in the third and fourth selected generations, were used in further selective breeding.
2.2.4 Combined selection
The test for mixed selection (within the limits of strain IR) was started in the fifth selection generation. For this purpose, family selection was carried out first (out of the four families obtained simultaneously, the two which appeared to be best were selected); then within the best families, the mass selection of champions was made (in the second year of life). Maturing males (out of those selected for breeding) will be checked according to offspring. It is hoped that mixed selection will enable acceleration of the process.
It is obvious from the review of the selection methods that reproductive crossings were mainly used. Back-crossing of hybrids with the Amur wild carp was performed in only one generation (third). In view of intensive inbred depression, attempts were made to avoid close inbreeding. In producing strain I considerable inbreeding was allowed, in which case the inbreeding coefficient for the fish of the fourth generation in strain I was approximately 0.25–0.3. The inbred depression appeared to be rather intensive. The number of spawners used for the reproduction of each strain was increased to prevent further inbreeding whenever possible, and two or more parallel crossings were made. These measures, as well as intensive selection, helped to decrease harmful effects of inbreeding in the fifth generation.
Mild inbreeding is inevitable while dealing with carp selection; but in combination with occasional crossings of fish from different strains and checking the spawners for combining ability, it may even prove to be useful.
The following means of marking were used: introduction of radioisotopes (Ca45), cutting of fins, branding (branding of marks and figures) and injection of various organic dyes.
Radioactive calcium was used for labelling fry for progeny testing. Larvae weighing 50 to 500 mg were placed for 1–1.5 hours in a solution of calcium chloride of 2 milli-curie/litre potency (Ca45 Cl2). The calcium deposited in bones distinguished the labelled fish from unlabelled ones for 3–4 months due to the radioactivity of the dried fins or dried skeleton (Kirpichnikov, et al., 1958).
Mechanical marking was widely used in combined breeding of fry obtained from many crossings. Fins (D, V, A or P) were cut under anesthesia when the larvae weighed 150–200 mg.
Branding on the body side was done both in groups and individually. When marking groups some common mark was used (0, □, ∆, and so on); when marking individuals, each fish had its own number. In the prevailing climatic conditions, the individual brandings remain distinct 3–4 years, while group marks may be identified even after 5–6 years. Branding did not hinder growth rate of the fish.
Organic dichlortriazine dyes were first tested on carp in 1967. The dye was injected subcutaneously in the abdominal area and remained there for 12 months. One may expect that kind of mark to last for longer periods (up to 2 years).
Due to inadequate numbers of experimental ponds for second-year and older fish, growing of different breed groups was usually done jointly, separate growing being practised only in the first summer. This prevented carrying out selection for fish productivity.
The results of separate and joint stocking in growing ponds generally appear to be rather close (Moav and Wohlfarth, 1967). The selection for growth rate had to result in the improvement of fish productivity in general.
The Ropsha carps of all three strains have a complete scale cover and are homozygous in respect to two genes (SSnn). There were no more than 10 percent of fish heterozygous in respect to gene S only among the spawners of group RI (fourth generation).
As to the remaining morphological characteristics, the Ropsha carps occupy an intermediate position between the cultivated carp and the Amur wild carp. As to the exterior characteristics, there is some difference between the strains. Reversive hybrids have a more elongated body and are much like the wild carp. The head of Ropsha carp is shorter than that of the original cultivated carp. When judged by the coefficient of condition ( or length-weight relationship) the Ropsha carp is similar to the Galician carp. This is especially true of strain I carps. The average indices for fingerling condition proved to be the following:
|4th selected generation R;||n||=||2.78|
|4th selected generation I;||n||=||2.98|
|5th selected generation I;||n||=||2.96|
|Amur wild carp (ponds)||n||=||2.51|
Two-year-old Ropsha carp are characterized by an evenly developed body both in height and in width. In the third year of life and especially later on, the shape of the body changes, and they become more and more like the wild carp.
Fecundity of Ropsha female carp is hardly different from the fecundity of other European strains of carp. Spawning goes on better than in non-hybrid carp at lower temperatures and the larvae endure well the transitory periods of cold (Kirpichnikov and Lebedeva, 1953; Kirpichnikov, 1966). On the 8–12th day after spawning, it is possible to collect as many as 100 000 larvae from one female in small spawning ponds, while in larger ponds the figure may reach 150 000 or even 200 000. The Ropsha carp inherited from the wild carp a tendency to partial spawning. Some spawners are able to yield within one year two or even three portions of eggs, but the second and third portions are usually small.
The fingerlings of all Ropsha carp strains grow rapidly, exceeding scattered carps by 10–20 percent in weight by autumn (in the environmental conditions of the Northwest), and even by 40–50 percent or more in cold years (Zonova and Shatrova, 1966, Romanova, et al., 1966; Kryazheva, 1969). The difference in growth rate was usually determined in the first month of the young fish's life (Fig.2). The Amur wild carp grow slower than the Ropsha carp. According to Kryazheva (1969) the fingerlings of the fifth selected generation (IR strain) are not inferior, in respect to growth rate, to hybrids of the first generation exhibiting heterosis.
The growth rate of two-year-old Ropsha fish differed little from the growth of scattered carp of the same age, though they lagged behind somewhat with intensive feeding. Later on, the Ropsha carp grew slower than the scattered ones; but their growth was faster than of the wild carp.
Fig.2 Rate of growth of fingerlings of selected and non-selected carp. Continuous lines - Ropsha carp; dotted lines - non-selected carp. 1 - Zavysochje, pond 2, 1960; 2 - Opochka, pond 1, 1961; 3 - Opochka, pond 1, 1962; 4 - Yazhelbity, pond 3a, 1965.
Ropsha carp in the first year of life showed high viability, especially the carp of strain R. Young hybrid fish (hybrids of strains I and R) had still higher viability.
Winter hardiness of Ropsha carp depends on the share of inheritance received from the winter-resistant Amur wild carp. Reversive hybrids endure winter better than interlinear ones. No heterosis was observed as to this character. The Ropsha carp of all generations appeared to be far more cold-resistant than the non-hybrid carps, but they were less resistant than the Amur wild carp. When the weight of hybrid fingerlings reaches about 20 g during the winter, they are culled (generally in excess of 50 percent); while few are culled when the weight reaches 50 g.
Fish productivity of the ponds in the Northwest where Ropsha carp are grown is as much as 300–600 (sometimes it reaches 1200) kg of fingerlings per hectare. The production of two-year-old fish is 200–900 kg per hectare (Table III). Data on fish production for 1966 and 1967 show a significant increase in recent years. This increase is partly due to replacement of non-selected carp by selected Ropsha breeds, as well as to improvement of technology of carp culture. Temperature factors were also important, and the years 1966 and 1967 were favourable in this respect.
Feeding of Ropsha carp differs somewhat from that of other carp. Zooplankton and artificial food (mainly vegetable feeds) are used to a lesser degree, benthos being preferred by the fish. Natural food is of importance in the diet of fingerlings.
Fish productivity of the ponds in commercial fisheries of the Northwest (kg/ha)
|Name of Fishery||Average fish productivity (kg/ha)|
|Novaya Ladoga and|
Note: In 1966 and 1967 almost the entire fish farm output was obtained from Ropsha carp production.
Unfortunately, there was an inadequate number of ponds in the breeding farms of the Yazhelbitsy and the Opochka, which gave rise to difficulties in the organizational activities.
Since 1960 reproduction of Ropsha carp brought from Ropsha has been going on continuously in both of these fisheries. Spawners of the two strains I and R have been brought into both breeding and commercial farms. A moderate inbreeding was allowed within each of the strains in the process of reproduction.
To prevent close inbreeding, mass spawning was performed; as a rule, a whole group of spawners was involved. In all breeding farms offsprings were obtained from spawners of each strain in turn; at the same time, for industrial purposes, mixed offsprings were obtained in large quantities.
Such crossings were advantageous due to the occurrence of some distinct heterosis.
Rearing of broodstock (two pure strains) accompanied by the simple mass selection measured the worth of the best specimens in the first and second year of their life. Normally from 1 to 10 percent of all fish grown was kept for breeding, the weight being the main indication in selection.
Abundant broodstock was reared in the Yazhelbitsy and the Opochka farms within a comparatively short time. In 1964 production spawning pairs was started in the breeding fish farms to be transported to industrial ones. In this process females of I group were mated with males of R group and vice versa, which enabled the conversion of all the pond fisheries of the Northwest to industrial hybridization. For three years about 500 pairs of Ropsha carps were transported from breeding farms to fisheries of the northwest and other regions of the country. The majority of spawners in the Northwestern fish farms are now Ropsha carp (Table IV).
Stock of carp breeders in pond fish farms of the Northwest (autumn 1967)
|Districts||Number of Ropsha carps||Number of carps of other origin|
|Total all fish||2237||328|
The experience gained from the 3-step system of breeding in the Northwest proved to be of greater advantage as compared to the routine procedure of breeding activity in all other farms. Apart from that, a number of shortcomings were observed, the main one being the danger of mass infections of disease in breeding farms.
The nutritional quality of Ropsha carps is high. They contain more fat and protein than Ukrainian carp (Tomilenko and Grechkovskaja 1967) and have a more piquant taste. The proportional weight of edible parts is the same as in other kinds of carp.
A detailed analysis of temperature influence on the fingerlings' growth and fish-productivity of nursery ponds carried out by Tolmacheva (1969) showed that temperature was the most important factor determining the growth and weight of Ropsha carp. The same relationship was established in respect to larvae and two-year-old fish. Thus, in the Kirov pond of the Ropsha fishery the following figures for fish yields (two-year-old fish) were obtained:
|Cold years||(1956, 1962 and 1965)||=||321 kg/ha|
|Warm years||(1957, 1958, 1961, 1963)||=||677 kg/ha|
|Hot summer||(1960)||=||890 kg/ha|
It is obvious that in the Northwest carp growth depends to a large extent on the temperature conditions of the year.
On the whole, the Ropsha carp (of the fourth and fifth selected generations) can be defined as a breed-group suitable for breeding in the Northwest. The introduction of these carp for cultivation extended the borders of carp breeding to 60° north latitude and made it possible to get consistent yields (leaving out certain very cold years) in the northwest regions of the of the U.S.S.R. Good results were also obtained in Ropsha carp breeding in Siberia and Estonia.
Nevertheless, Ropsha carp breeding has some limitations because the effect of the breeding is largely determined by air temperature in summer months. Hence, the most important task of future work is the further enhancement of cold-resistance and winter-hardiness in this breed-group. It is necessary to decrease to a minimum the dependence of the rate of carp growth on temperature variations.
Until recently there has been no selective breeding of carp in the farms of the Northwest. Carp were of mixed, non-selected strains; and each fishery was breeding its own stock. A lack of ponds suitable for the purpose and the poor skill of fish-breeders resulted in inadequate selective breeding which negatively affected the quality of spawners.
The availability of a selected breed-group of Ropsha carp in the experimental fishery of Ropsha made it possible to start planned breeding of carp in the three districts of the Northwest (Novgorod, Pskov and Leningrad) in the last decade. A three-step system of breeding was devised as the basis for the organizational activity, the fisheries being divided into three groups (Kirpichnikov, 1960b, 1966; Golovinskaya, 1962, 1966).
selected fish farms of the highest standard dealing with the development of new breeds of carp (in this case the experimental fishery of Ropsha);
breeding farms reproducing this breed (earlier they were Yazhelbitsy and Opochka fisheries; since 1966 it is the Ropsha fish farm);
commercial farms which do not grow their own spawners but get their supply of spawners from the breeding farms (all the other farms of the Northwest).
Such infections occurred both in the Opochka and in the Yazhelbitsy breeding farms and hindered the distribution of broodstock from these farms. It should be pointed out that the main cause of infections was the lack of suitable ponds (ponds for broodstock storage, spawning, quarantine, and other purposes) in both breeding farms. The control of infections in breeding farms would be successful if certain measures are taken:
constructing special ponds and raising breeding stock in isolated pond areas;
increasing carp resistance to infections by special selection procedures;
improving the system of sanitary preventive and treatment measures;
extensively using the large-scale application of carp fry rearing under hatchery conditions (Konradt and Sakharov, 1966). Natural spawning has been replaced by artificial spawning of eggs and subsequent incubation of them in mechanical incubators.
The application of these measures will make it possible to increase the efficiency of the 3-step system of breeding in carp culture.
Thus the introduction of the system in question in the Northwest made it possible to substitute nearly all non-selected carp stocks in the industrial fish farms by selected broodstock. It resulted in a substantial increase in the productivity of ponds.
Breeding work with Ropsha carp is now progressing in other regions of the U.S.S.R. as well- in Estonia, West Siberia and the Krasnodar territory in particular.
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