by
K.A. Golovinskaya
All-Union Pond Fishery Institute
Moscow, U.S.S.R.
Breed is a very customary term, but is rather difficult to define adequately. In a biological sense, this term implies a group of farm animals related by origin and characterized by certain breed characters which allow them to be distinguished from each other and evaluated in regard to their usable properties. The following description of breed is found in a well-known manual on cattle breeding (Handbuch der Tierzüchtung, W. Herre, vol.3, chapter 1. 1958–61). Breeds are secured from incidental crossings of widely spread strains or species which differ quite greatly from each other in some characters and hereditary properties. These are collective individuals whose peculiarities can be defined only with the help of statistical methods."
Population genetics is the theoretical basis of the current methods of creating new breeds of domestic animals and cultured plants (N.P. Dubinin and J.L. Glembotsky, 1967). The breeds of domestic animals, when considered from this view point, represent complicated polyheterozygous populations. Their genetic structure is being built as a definite system which is maintained by purposeful selection, i.e., keeping of desirable and discarding of undesirable genotypes.
Such genetic systems should be sufficiently flexible to allow a reconstruction, for instance in response to changes in the purpose of breeding or in the extension of the habitat. At the same time, it should ensure the genetic integrity which is inherent in a given breed and makes the latter differ from other breeders of the same species. Similarly, as in the case of a natural population, we can apply here the notion of genetic homeostasis (Lerner, 1954, 1958) which ensures the viability of a population under changeable conditions of existence and is based on a number of genetic adaptational mechanisms. Among the most important biological mechanisms of that type is one of maintaining a sufficient level of heterozygosis, which not only secures a genetic diversity within a population, but rather frequently gives rise to the heterosis effect.
These properties of the genetic structure of the cultured species form the basis for their plasticity which admits reconstructions in a desirable direction, sometimes very promptly. At the same time, they can impede to some extent the process of selection due to the presence of balanced (heritably fixed) heterozygous systems as demonstrated for carp (Kirpichnikov, 1968).
It has to be emphasized that for proper understanding of the essence of breed it is not sufficient to know its biological characteristic only. The animal breeds like plant varieties are not only biological but economic categories as well. They both are formed under the influence of environmental conditions and activity of man. The latter becomes more important in the process of development of the productive forces which is followed by the development of productive animal breeding and agriculture. The highly productive breeds and varieties created with the help of artificial selection under certain conditions and for a certain purpose are among the means of agricultural production which increase labour productivity.
Summing up the above, we can define breed as a man-created population which is characterized by certain heritably fixed characters (level of productivity, biological features, external and morphological characters).
The type of these characteristics is determined by the purpose of breeding and utilization of a breed, whereas the degree of their stability is conditioned by the genetic structure of the population and their own genetic nature.
It has to be kept in mind that the main properties of a breed manifest themselves in their most typical form under the conditions which existed when this breed was created. It concerns, particularly, the physiological characters (growth rate, food conversion, etc.).
A breed, which is productive from the standpoint of some characters, may not always be the best one under different conditions. It is easily illustrated by numerous examples from animal farming. The problem is to find a breed adopted to local conditions.
The local races played an important part in the development of animal production, and even now have not lost their significance. Natural selection was of greatest importance in their formation (primary in the beginning) and it was also closely connected with their properties, like high adaptiveness, tolerance, food searching activity, and remarkable survival under local conditions. But at the same time, some of them had developed such genetic systems which hardly respond to the effect of artificial selection. Indeed, this cannot apply to all evolving breed groups. Frequently we can find in any area animals originating from cultured breeds that had been introduced but have lost their high productive properties as a result of improper selection.
However, there are many examples of creations of stable and productive forms well adjusted to local conditions by applying the system of crossing and selection. A well-known example is the creation of the new breed of cattle, Santa Gertruda, in the hot climate of Texas, U.S.A. This breed was obtained by crossing short-horns with zebu (Bos indicus) introduced from India. Among the merits of this new breed was the resistance to infections spread by ticks. It can be attributed, evidently, to the thick skin and short hairs which make an animal less attractive to the insects. Such animals seem to repel the ticks and become subject to infection in small, immunizing dozes. This situation is dealt with in detail in the book “Genetic Resistance to Disease in Domestic Animals” by Hutt (1958), which can be recommended to all selectionist-ichthyologists.
In the very beginning of cattle breeding activity, easily distinguished and rather constant marks such as colouring and its pattern, hornlessness of cattle, etc., served as a guide to identify different breeds or stocks of different owners. Later they assumed significance variously as the mark of origin, trade mark, and race characters etc. upon which the most severe requirements were placed, sometimes very harmfully. It sharply limited the possibilities of selection on the basis of really valuable characters. Moreover, many natural markings, which seemed at first glance insignificant, proved to be related to very important physiological properties. Examples of the effect of such unidirectional selection are cited in the book “Population Genetics and Selection” by N.I. Dubinin and J.L. Glembotsky (1967).
Though fish culture has been in practice for centuries in Europe and thousands of years in China, stable and specialized strains have not been produced as yet even among carps which are the only group of pond fish that have been subjected to experiments in selection.
Carp culture in China, occupies a secondary position (carp constitute a part of poly-species culture). Unfortunately, we have at our disposal quite incomplete information of carps cultivated in the eastern and south Asian countries. According to the available data it appears that there is a diversity of forms there which differ in colour, external characteristics and peculiarities of scale covering. They are evidently indigenous breeds. Their differentiation is based on heterozygosity of these characters, which is inherent in carp, rather than on purposeful selection. Very interesting is the recently discovered homologous genetic variation controlling scale patterns in European, south Asian and Japanese carps derived from different subspecies of wild carps (Kirpichnikov, 1967; Djan din Djong (1967) and our unpublished data).
According to the pattern of scale covering four basic forms (races) of carps are distinguishable: completely covered with scales, with scattered scales, with scales arranged in line, and scaleless, which are referred to as scaled, scattered, linear and leather carp (Kirpichnikov and Golovinskaya, 1966; Schäperclaus, 1961).
These four categories are determined by the combination of two pairs of independent hereditary factors (S-s and N-n genes) which are obviously identical for European and Asian carps.
The west European carp has been studied extensively and described in detail in the literature, which in particular indicates that there were attempts to classify and even to standardize carp (Schäperclaus, 1961) according to a body shape index or conformation factor i.e., the ratio between standard length and maximum height. In the case of cultured carp the index was assumed as ranging from 2 to 3, and the carp were divided into high-backed (l/h = 2 – 2.6) and wide-backed (l/h = 2.6 –3).
After the First World War, the German Agricultural Union (D.L.G.) made an attempt to establish standard factors for the four major races which had been recommended for breeding. Those indices included almost all the above characteristics of body shape and also the features of scale covering.
The high-backed Aischgrund and Galician carps were rated highest in value (it was suggested that there is a direct relationship between growth rate and body height), followed by wide-backed Lowseetian and Frank carps.
According to pattern of scale covering, these standard forms were assumed: leather for Aischgrund and Frank linear for Galician and scaled for Lowseetian.
Along with investigations into genetic variability of carp, attempts were directed at creating the Ukrainian carp (framed and scaled). This work was carried out by Ukrainian selectionists headed by A.I. Kuzama.
Ukrainian carp belong to high-backed breeds. When food supply is adequate the conformation factor reaches 2.2–2.3 (or 2.0 sometimes), and there is good growth and high production.
Typical framed carp have the scales arranged in the shape of a frame composed of a dorsal row and patches located near the head, on the tail and near the anal and ventral fins. Their disadvantage is low resistance to infectious dropsy (a serious and widely spread infection); besides, they are heat-loving and do not satisfactorily withstand the winter in northern areas.
Creation of cold resistant carp breeds is one of the important problems of carp culture in the U.S.S.R. For this purpose the most promising race of wild carp has been sought since the thirties. Investigations carried out under the guidance of V.S. Kirpichnikov showed that Amur wild carp (Cyprinus carpio haematopterus) is the best form for use in hybridization of carp. The hybrids of the first generation have gained recognition as a commercial breed. They are noted for remarkable cold resistance, high viability and fast growth rate.
The heterosis effect in growth and viability of these hybrids can be observed in the first year (especially during the first months) of their life. The principal disadvantage of this commercial hybrid is that both the initial forms (selected carp and wild carp) should be kept at rearing farms because the hybrids are not preserved for further breeding.
Under the conditions of commercial hybridization conducted on a large scale, the stocks become intermingled and naturally the efficiency of selection is lost.
Selected hybrids of cultured carp x Amur wild carp have been produced to the fifth generation (applying a special scheme of crossings) and resulted in the creation of a new breed group which gained the name of Ropsha (after the name of the experimental farm where the work was conducted), or Northern carp. These carp now constitute the main pedigree stock for the northwest region of the Rudsian Federation, and are cultivated in Estonia and Siberia. In the Ukraine, when crossed with local carp they showed a strong heterosis effect.
In the South, Ropsha carp grow well, and what is most interesting, they and their hybrids between local strains are more resistant to dropsy than local carp. Ropsha carp have the entire scale covering and genetically are homozygous. Carp with scattered scales participated in initial crossings. In the process of selection, a special segregation check was performed with a view to choosing homozygous producers. In diagnostic characters these carp occupy a place between common carp and Amur wild carp. The conformation factor (1/h) in parents varies within the limits 2.9–3.3, while in Amur wild carp it ranges from 3.2 to 3.6 and in the common carp from 2.7 to 3.0. Ropsha carp are not inferior to Ukrainian carp in respect to fecundity.
Other hybrid groups of carp of similar origin in the fish farms of the U.S.S.R. (Kursk carp, for example) were not subject to special selection, and cannot therefore be regarded as belonging to any special breed group.
Experiments aimed at creating new breeds of carp are being carried out in Byelorussia with a view to obtaining a pure carp strain. Similar work is being conducted at the Research Institute of Pond and River Fisheries for raising a mid-Russian strain of carp.
The main object of intensive trout culture is rainbow trout (Salmo irideus) which is a river form of an American species Salmo gairdneri and other related varieties.
This classification was extremely artificial and was rightly criticized. The selective value of body features had been reestimated by Spiczakov (1935). It proved impossible to gain the required uniformity in the progeny of linear and leather carps (except the Aischgrund race). The reasons of this failure became clear after the fission scheme by scale genes had been studied.
The groups of carp intended for breeding were not sufficiently stable and uniform in their characters and properties to qualify as developed breeds or even evolving breed groups, the only exception being the Aischgrund carp. This carp deserves special mention although it does not exist now in a pure form. Its history is rather amusing (Hofmann, 1927; 1937).
Aischgrund carp is a confined local form which had been reared in the south of Germany in Bavaria. Its habitat covered only 2 000 ha of pond surface within the area of about 500 km2. Breeding of this carp was undertaken by small peasant farms, and market facilities were very limited. Trade relations between the farmers and middlemen sometimes lasted for centuries.
The culture of pure bred Aischgrund carp was carried out in the course of hundreds of years, as indicated in medieval literature. It was the most scaleless and at the same time the shortest high-backed carp among all known cultured carps with the main conformation factor (1/h) at 1.7. Its specific plate shape was so popular among the consumers that in all regions of Bavaria special selection was conducted with the aim to draw other carp strains nearer to the Aischgrund type. This was to cater to the traditional local method of baking the fish whole.
However, the body height of Aischgrund carp was not correlated with good development of the dorsal musculature but by a distortion of the vertebrae. The genetic nature of Aischgrund carp unfortunately remains unknown.
In general, Aischgrund carp was noted for a weak constitution and was inferior to other carps in growth rate and viability, especially under more severe environments than that in its native habitat.
However, when it was suggested that the Aischgrund carp be replaced by another more productive breed, local fish breeders seriously objected. This dispute was reflected in the German fisheries press in 1935–37.
Thus, we can see that this peculiar and, in fact, low productive local strain had been created and maintained by the following well-defined factors: unilateral long-term selection with undoubted close inbreeding under conditions of isolation brought about by limited habitat and a conformity to market requirements.
The tendency to raise high-backed, scaleless forms is characteristic of the west European carp culture and the features of Aischgrund carp can be traced in many carp stocks. Sometimes it is a result of crossing with the Aischgrund carp. West European carp culture became highly mixed during the Second World War. Therefore, the differences between the stocks almost disappeared, and it appears that now there are no stable breeds at all.
Schäperclaus (1961) considers, for example, that genetic diversity in the carp stocks in Germany is very limited. At the same time, in a number of fish farms in west European countries with well developed carp culture, there are good local lines which can be used in selection work.
In the U.S.S.R. there are several more or less developed breed groups of carp of pure and hybrid origin (crosses with Eastern wild carp). Their creation was determined by the demands of the fast growing pond fishery and the diversity of climatic conditions of the Soviet Union. In this connection major importance is being attached to the problem of area-wise division of breeds, based on studies of the four basic genetic groups of carp which mainly constitute the U.S.S.R. carp stocks and most European stocks as well.
Geneticist-ichthyologists have established certain regularities of inheritance of the main types of scale covering in carp. It was ascertained that scaled, scattered, linear and leather carp differ from each other, not only in their external and anatomical features, but in the most important commercially valuable properties, such as viability and growth.
Since it became known that these four major forms are obviously distributed throughout the whole habitat of cultured carp, we have found it expedient to give the description of their main diagnostic characters and gene segregation scheme. The appropriate references can be found in a brief summary of breed groups of carps in the U.S.S.R. (Kirpichnikov and Golovinskaya, 1966).
Scaled carp, like the wild carp races, have the entire scale covering. Small scales of even shape cover the whole body by rows in three directions, the number of rows being strictly constant. Minor irregularities in the distribution of scales (shifts) are admissible, while considerable distortions are undesirable, since they are often indicative of slow growth and low viability.
Scattered mirror carp has the most variable scale pattern. Carp with the least number of scales are proposed to be denoted as scattered carps of group I. Their scales are arranged in one row along the back and in separate patches at the base of fins and on the tail. In the middle part of the body the scales are either absent or occur isolated, the size of these individual scales may be small or large.
The most widely distributed carp in the U.S.S.R. are the scattered carp with more or less developed rows of scales located on the sides of the body, primarily along the lateral line. Carp with continuous or interrupted side row of scales, conspicuously halved (double mid-row), constitute group II. The carp with whole, large scales located along the lateral line (large mid-row) belong to group III. They grow more rapidly than the carp of group II. Besides these occur specimens whose bodies are entirely covered with scales arranged in proper horizontal rows. They differ from scaled carp in the larger size of scales (consequently, their smaller count in mid-row) and in the absence of clearly indicated diagonal rows.
The selection values of different groups of carp with scattered scales are not yet estimated. Carp of group I are usually regarded as most promising for selection. Recently obtained data on some properties of the third group of carp show that there are not sufficient grounds to consider carp of group I as a general and compulsory standard form for breeding.
Linear mirror carp form a well defined group. Besides the back row of scales, which begins at the head or the base of the dorsal fin, these carp always have a very accurate row of scales along the lateral line. These scales are usually stretched in vertical direction and flattened horizontally. The number of scales is important in identification. In addition to the linear row, there are more or less full rows of very even scales above and below the lateral line. Sometimes linear carp occur with the whole body entirely covered with neat rows of scales. They are very difficult to distinguish from scattered carp belonging to group III. Only the count of scales along the lateral line is of assistance in identification.
Leather carp are noted for the meagre number of scales. As a rule, such carp have the incomplete row of small scales beginning at the base of the dorsal fin, and several scales located near the head and on the tail. Sometimes leather carp have a few scales on the sides. The skin of leather carp is thicker than that of scattered carp; the lateral line is thinner and looks like a narrow branched line. Some leather carp are hardly distinguishable from carp with scattered scales of group I.
Linear and leather carps differ very much from scaled and scattered carps in the structure of fins, gills, pharyngeal teeth and in some other features (Table I). The dorsal and anal fins in these carp are sharply reduced. One or several rays in the mid part of the dorsal fin is often missing (sometimes the posterior part of the fin is reduced). The number of branched rays in the anal fin, and sometimes the size of the fin itself are reduced.
Table I
MAJOR DIAGNOSTIC CHARACTERS OF THE MAIN CARP VARIETIES
| Characters | Scaled | Scattered | Linear | Leather |
| Fin structure | Normal | Normal | Partially reduced | Partially reduced |
| Number of soft (branched) rays in fins | ||||
| dorsal | 16–24 | 16–24 | 10–21 | 4–20 |
| anal | 5(4) | 5(4) | 3–5 | 3–5(2) |
| Number of gill rakers on the first arch (outer row) | 23–30 | 22–28 | 16–23 | 16–21 |
| Arrangement of pharyngeal teeth | 1.1.3–3.1.1 (rarely1.1.3–3.1) | 1.1.3–3.1.1 (rarely1.1.3–3.1) | 1.1.3–3.1 1.3–3.1 | 1.1.3–3.1 1.3–3.1 |
| Number of lateral scales line | 34–41 | 32 | 32–39 | - |
| Factor 1/h1 in yearlings (Common carp) | 2.5–2.7 | 2.45–2.65 | 1.65–1.85 | 2.6–2.8 |
The linear and leather carps have an average of 4–5 gill rakers. Their pharyngeal teeth are undersized and the number is reduced by 1–3. They have only one or two rows of teeth instead of the three inherent in other carps.
The number of scales along the lateral line of linear carp is slightly less than that in scaled carp. Scattered carps of groups II and III almost never have over 32 scales along the lateral line.
The body shape of linear and leather carps is noticeably changed: the body stretched lengthwise, the conformation factor (1/h) is high. According to body height carp fingerlings can be arranged in the following order: scattered, scaled, leather, linear. There are slight differences in the measurements of girth, length of the dorsal fin, total length of gut and in some other characteristics.
Carp of the four genotypes are arranged in the following succession according to growth rate: scaled, scattered, linear, leather. If the weight of scaled carp is taken as 100 percent, the weight of carps of all other groups, under standard feeding conditions, will be approximately 95, 85 and 80 percent respectively. Under unfavourable conditions, however, these differences will greatly increase. The survival rate shows the same patterns: scaled carp come first (according to O group fish), while leather, and especially linear carps are less viable. In resistance to cold scaled carp again rate first while leather and linear carps show low resistance to winter freezing. Linear carp cannot winter in the northern areas at all.
In productivity, scaled and scattered carps show best results and are almost on the same standard.
In fecundity, linear and leather carp give way to scaled and scattered, if crossed between each other (linear × linear, linear × leather, leather × leather). Fecundity decreases in these cases by 25 percent due to mortality of embryos with genotype NN. The regularities of inheritance of scale covering are conditioned by a composition of two pairs of independent hereditary factors:
| SSnn and Ssnn | - | scaled carp |
| ss nn | - | carp with scattered scales |
| SSNn and SsNn | - | linear carp |
| ss Nn | - | leather carp |
Genotypes: SSNN, Ss NN and ss NN, are not viable.
Knowing genetic formulae of carps one can easily predict results of any crosses (Table II). According to the majority of crosses, two versions are presented: the first applies to homozygous spawners, the second to heterozygous parents. It is seen from Table II that only scaled and scattered carp could be homozygous by the main factors mentioned above and would not give rise to segregation in their progenies with respect to scales.
Linear and leather carps cannot produce a homogeneous generation: leather x leather will always produce leather and scattered carp, whereas linear × linear will produce linear and scaled or all the four forms.
In the U.S.S.R. linear carp are discarded, the culture of leather carp is practised only in the south, and only scaled carps are recommended for rearing in the north.
Table II
THE RESULTS OF CROSSES OF CARPS WITH DIFFERENT SCALE COVERING PATTERNS
| Parents | Progeny in percentage | |||
| Scaled | Scattered | Linear | Leather | |
| Scaled × scaled | 100 | - | - | - |
| Scaled × scattered | 100 | - | - | - |
| Scaled × linear* | 50 37.5 | - 12.5 | 50 37.5 | - 12.5 |
| Scaled × leather* | 50 25 | - 25 | 50 25 | - 25 |
| Scattered × scattered | - | 100 | - | - |
| Scattered × linear* | 50 25 | - 25 | 50 25 | - 25 |
| Scattered × leather* | - | 50 | - | 50 |
| Linear × linear* | 33.3 25 | - 8.3 | 66.7 50 | - 16.7 |
| Linear × leather* | 33.3 16.7 | - 16.7 | 66.7 33.3 | - 33.3 |
| Leather × leather | - | 33.3 | - | 66.7 |
Note: asterisks indicate crosses not recommended in carp culture.
In the end of the last century, specimens of three species were introduced to Germany (Schäperclaus, 1961). They differred in spawning time and in morphological characters. Due to disorderly crossings, they did not remain pure, and a suggestion was made to assign the German rainbow trout to an independent systematic category - Salmo irideus forma germanica. Now it appears possible to distinguish two major types of trout, shasta and steelhead. According to diagnostic characters and spawning periods, they stand close to the introduced species. Both types are clearly distinct in regard to their growth rate and resistance to disease, but the steelhead (evidently related to S. gairdneri by origin) is superior in respect to these characters. It must be noted that this strain of rainbow trout has acquired great importance in the U.S. sport fishery. With proper selection it became possible to improve some significant characters of this strain, including fecundity.
Thus, a favourable situation for selection has been created in trout culture, but no stable breeds or breed groups have been established so far.
It can be said in conclusion that in fish culture there are favourable conditions for development of breeding and selection. The extent of domestication of fishes is extremely low in comparison with other animal breeding. The world has tremendous natural resources in this field for the culture and domestication of fishes.
The intensification of fish culture is going on rather rapidly, and there is a powerful stimulus for furthering selection activity.
Therefore, the problems of theory and practice in the field of selection and breeding acquire primary importance for fish culture. Our mutual efforts should be directed at focusing attention on these problems and providing material facilities for their practical solution.
Djan din Djong, 1967 Data on the intraspecific variability, biology and distribution of the carp in North Vietnam (Dem.rep. of Vietnam). Genetics (USSR), 2:48–60
Dubinin, N.P. and J.L. Glembotsky, 1967 Population genetics and selection. Moskva, Nauka: 591 p.
Herre, W., 1961 The conception of species and race. In “Handbuch der Tierzüchtung”, Hamburg u. Berlin, P. Parey, 3(1); Russ. transl. Moskva, Kolos, 1965:11–33
Hofmann, I., 1927 Die Aischgründer Karpfenrasse. Z.Fisch., 25(3):291–365
Hofmann, I., 1937 Leistungszucht tut Not. Allg.Fisch.Ztg., 62(2):21–4
Hutt, F.B., 1958 Genetic resistance to disease in domestic animals. Ithaca, New York. Comstock Publ.Assoc., 198 p.
Kirpichnikov, V.S., 1967 Homologous hereditary variability and evolution of the carp (Cyprinus carpio L.). Genetics (USSR), 2:34–47
Kirpichnikov, V.S., 1968 Efficiency of mass selection and selection for relatives in fish culture. FAO Fish.Rep., (44), vol.4:179–94
Kirpichnikov, V.S. and K.A. Golovinskaya, 1966 Characteristics of major breed groups of carp of the USSR. Izv.gosud.nauchno-issled. Inst.ozer.rech.ryb.Khoz., 61:28–39
Lerner, I.M., 1954 Genetic homeostasis. New York, John Wiley and Sons. 134 p.
Lerner, I.M., 1958 The genetic basis of selection. New York, John Wiley and Sons, 298 p.
Schäperclaus, W., 1961 Lehrbuch der Teichwirtschaft. Berlin, P. Parey, 582 p.
Spiczakov, T., 1935 Zum Problem der Rasse und des Exterieurs beim Karpfen. Z.Fisch., 33(3):409–72
