I/RR-5
THE STATUS OF WARM-WATER POND FISH CULTURE IN EUROPE

by

J.L. GAUDET
FAO Assistant Regional Fishery Officer for Europe¹
Rome, Italy

THE STATUS OF WARM-WATER POND FISH CULTURE IN EUROPE

Abstract

In the European region, fish culture in warm-water ponds goes back to the Middle Ages and, in France and Spain particularly, was closely tied to religious practices of the time. By scientific management and careful selection, it is now possible to obtain yields as high as 3,500 kg/ha for carp. The experimental culture of cold-water species such as trout, in water having a temperature of between 26,9°C and 29°C also give interesting results in Spain.

Although the purpose of fish culture in Europe is often restocking natural waters for sport and commercial fisheries, much intensive fish culture, oriented primarily towards food production is also carried out. Artificial feeding is widely practised. Gains obtained by feeding are hard to determine but in Israel, of 2,000 kg of fish obtained per hectare, probably 400 kg come from natural food, 400 kg more from fertilizers and 1,200 kg from artificial feeding. The food coefficient varies with the size of fish, so advanced methods require the sampling of the weight and rate of growth of the fish regularly. Stocking material usually comes from each country's own production, although new species are sometimes imported.

In most European countries, governmental assistance is given to fish culturists, either through the establishment of research institutes and experimental stations or in the form of direct financial assistance. In eastern Europe, the governments act as the central planning agencies for fish culture development.

The main problems facing warm-water fish culture in Europe are the inadequacy of water supplies, particularly in Poland and Israel; water pollution and fish diseases in western Europe. A list of species used for warm-water fish culture in Europe is given.

SITUATION DE LA PISCICULTURE EN ETANGS A TEMPERATURE ELEVEE EN EUROPE

Résumé

En Europe, l'élevage du poisson en étang à eau à température élevée remonte au Moyen Age. En France et en Espagne, notamment, il se rattachait étroitement aux pratiques religieuses de l'époque. Un aménagement scientifique et une sélection attentive permettent actuellement d'obtenir des rendements de l'ordre de 3 500 kg/ha pour la carpe. La pisciculture expérimentale, dans des eaux dont la température va de 26,9 à 29°C, d'espèces d'eau froide comme la truite donne également d'intéressants résultats en Espagne.

Si la pisciculture européenne vise fréquemment au repeuplement d'eaux naturelles à des fins sportives ou commerciales, il n'en existe pas moins une importante pisciculture intensive, orientée principalement vers la production alimentaire. L'alimentation artificielle est très répandue. Il est difficile d'évaluer exactement les gains obtenus par le nourrissage, mais par exemple en Israël, sur une production de 2 000 kg de poisson à l'hectare, on peut sans doute considérer que 400 kg viennent de l'alimentation naturelle, 400 kg de l'apport d'engrais et 1 200 kg de la nourriture d'appoint. Le quotient alimentaire variant avec la taille du poisson, les méthodes modernes exigent des sondages périodiques sur le poids et le taux de croissance. Bien que l'on importe parfois de nouvelles espèces, le matériel utilisé pour le repeuplement provient généralement du pays même.

Dans la plupart des pays d'Europe, les pisciculteurs reçoivent un appui des pouvoirs publics, soit par la création d'instituts de recherche et de stations expérimentales, soit sous la forme d'une assistance financière directe. En Europe orientale, l'Etat assure la planification centrale du développement de la pisciculture.

La pisciculture européenne en eaux à température élevée se heurte principalement aux difficultés suivantes: insuffisance de l'alimentation en eau, particulièrement en Pologne et en Israël, pollution des eaux (Europe occidentale), et maladies des poissons.

La communication renferme une liste des espèces utilisées en Europe en pisciculture en eaux à température élevée.

SITUACION DE LA PISCICULTURA EN ESTANQUES DE AGUA TEMPLADA EN EUROPA

Extracto

En la región europea, la piscicultura en estanques de agua templada se remonta a la Edad Media, y, especialmente en Francia y Espanã, estaba estrechamente ligada a las prácticas religiosas de la época. Mediante la explotación en forma científica y la selección cuidadosa, actualmente es posible obtener rendimientos que llegan a ser de 3.500 kilógramos por hectárea para la carpa. El cultivo experimental de especies de agua fría tales como la trucha en aguas con temperaturas de 26,9°C y 29°C está dando también resultados interesantes en España.

Aunque la finalidad de la piscicultura en Europa es casi siempre la de repoblar las aguas naturales para las pesquerías deportivas y comerciales, también se llevan a cabo intensamente muchas actividades pisciculturales orientadas principalmente a la producción de alimento. La alimentación artificial se practica ampliamente. Es diffcil determinar las ventajas obtenidas con la alimentación artificial aunque en Israel, de 2.000 kg de pescado obtenidos por hectárea, probablemente 400 kg proceden de la alimentación natural, 400 kg más de los fertilizantes y 1.200 kg de la alimentación artificial. El coeficiente de alimentación varía según el tamaño del pez, por lo que los métodos modernos requieren el muestreo en forma regular del peso y tasa de crecimiento de los peces. El material para la repoblación procede generalmente de la propia producción de cada país aunque a veces se importan especies nuevas.

En la mayoría de los países europeos se presta ayuda oficial a los piscicultores ya sea mediante la creación de institutos de investigación y centros experimentales, sea en forma de ayuda económica directa. En Europa oriental, los gobiernos actúan como organismos de planificación centralizada para el desarrollo de la piscicultura.

Los principales problemas con que tropieza la piscicultura en aguas templadas en Europa son la insuficiencia del suministro de agua, particularmente en Polonia e Israel, la contaminación de las aguas en Europa occidental y las enfermedades de los peces. Se da una lista de las especies utilizadas para la piscicultura en aguas templadas en Europa.

¹ Present address: Fishery Officer, Inland Fishery Branch, FAO, Rome

1 THE REGION

Geographically the European region is defined as the land and water areas lying between the Arctic ocean in the north, the Atlantic ocean in the west, the Mediterranean and adjacent seas and the Caucasian mountains in the south and the Caspian sea and Ural mountains in the east.

The following countries are in the European region:

* not member of FAO

This paper is based on replies to a questionnaire sent to FAO member countries in the region practising warm-water pond fish culture. Replies were received from Belgium, Denmark, France, Federal Republic of Germany, Israel, Italy, the Netherlands, Poland, Romania, Spain and Yugoslavia.

2 DEVELOPMENT OF FISH CULTURE

European warm-water pond fish culture goes back to the Middle Ages. Fish ponds were often located near monasteries, such as the one at Grandjilla near San Lorenzo del Escorial in Spain, to provide “lean meat” during Lent which, at that time, was rigorously observed. The development of warm-water fish culture in Europe is often identified with carp culture. It is said that it was in the Middle Ages that carp was imported from the Orient via Cyprus, hence the name Cyprinus. Others claim that carp and its culture were introduced into Europe from China in the sixteenth century. According to certain authors carp is a component of the palaearctic fauna from the Danube system at least 1,500 years ago. Carp is also mentioned in the “Capitulare de Villis” of Charlemagne in 812 and by the German Kaiser, Rudolf II (1576–1612). Carp culture in Europe developed independently of that in the Far East with different culture methods.

In Romania, primitive fish culture has been practised since a very long time, but was limited to rivers and lakes. Documents concerning these activities go back to the twelfth century. Primitive fish culture in ponds developed parallel with the development of water mills. As soon as the water mills were motorized, the interest in pond fish culture decreased. In that country modern fish culture practices were introduced only after 1950.

In Italy and Greece, warm-water fish culture is practised in brackish-water lagoons where salinity can sometimes be regulated. In Italy, it takes place mostly along the coast off central and southern Italy and in Sardinia. Warm-water fish culture is also practised in Italy in rice fields in northern Italy during the warm summer months. Brackish-water fish culture is carried out in Israel.

Modern fish culture started in 1864 in Spain with the publication of the Manual practico de Piscicultura by Mariano de la Paz Graells who built in 1886 near Segovia an ichthyological laboratory for the culture of trout to stock streams and lakes. The Cuerpo de Ingenieros de Montes was made responsible for all work relating to fish breeding and restocking. In the same year, 1886, the private fish farm of the Monasterio de Piedra, near Zaragoza, was built for trout culture.

Pond fish culture is new in the Netherlands, Israel and Yugoslavia. In the Netherlands, it dates back to the nineteenth century. It expanded gradually and in 1963 the breeding areas were doubled by the construction of a new pond farm. At present, there are four fish breeding stations, with a total area of 320 ha used for warm-water fish culture. The fish raised in those farms are used exclusively for stocking rivers and lakes for sport and commercial fisheries.

In 1939, 15 ha of fish ponds were constructed in Israel. They yielded an average of 1,000 kg per ha. Since then, the extension of fish farming has been very rapid and today there are 4,800 ha under cultivation. In Israel, there are great limitations in pond building because of the shortage of fresh water and so brackish water is also utilized for fish culture.

Warm-water fish culture was introduced in Yugoslavia in the beginning of the twentieth century. Three varieties of the common carp (Cyprinus carpio) (scale carp - “schupner”, big scale carp - “leder”, and carp without scales - “spigler”) were introduced in Yugoslavia from Poland and Czechoslovakia. There was no tradition of fish culture in the country before this. Fish culture is concentrated historically around the big rivers, the Danube, the Sava, the Drava and the Tisa, in the provinces of Slovenia and Vojvodina. The fish farms are very big. After the second world war, fish farming developed rapidly and now the area covered by fish farms is double that of the pre-war period, i.e. more than 10,000 ha.

3 LIST OF SPECIES USED FOR WARM-WATER POND FISH CULTURE IN EUROPE

* In Italy only eels and Mugil are cultivated in brackish water, the other species are not cultivated but caught in warm-water ponds

¹ Imported in 1966 from Argentina
² Very few in numbers, no commercial value
³ Imported from U.S.S.R. in 1964
⁴ Small quantities for export
⁵ Accounts for 97 percent of pond production
⁶ For stocking natural waters only
⁷ Fancy fish for parks
⁸ For market and for stocking natural waters only
⁹ Cultivated in brackish warm-water ponds
¹⁰ Cultivated in warm-water ponds on a trial basis

4 REVIEW OF THE HIGHLIGHTS IN FISH CULTURE IN EUROPE

Belgium

There are no particular highlights worth mentioning in the progress of fish culture in Belgium. Progressively, the techniques were improved, as in the case of most European countries: scientifically controlled stocking, artificial feeding, use of fertilizers, artificial fertilization, introduction of new species such as the rainbow trout (Salmo gairdneri), and efficiency of transportation methods.

France

Two outstanding practices adopted in carp culture in France are (i) the general use of lime and phosphate fertilizers, and (ii) the use of royal carp (Cyprinus carpio var. royal). The following formula based on the hydrotimetric degree ¹ of ponds has been worked out for the application of lime: K = 20 h (15 - D H); h being the depth of the pond at the sluice gate; D H the hydrotimetric degree and K the quantity of quick-lime required.

Since about 1920, a selected carp race derived from stocks originating in central Europe and called royal carp has been in use in France. It is characterized mostly by the length/weight ratio, which is no smaller than 2.6. The head is small in relation to the body and the back is curved.

Greece

In Greece, efforts are directed towards increasing production by use of artificial fertilizers and improved sites.

Israel

With the application of scientific knowledge and the careful adaptation of European fish culture methods to the particular climatic, water and soil conditions of Israel, it has been possible to raise the average yield from 1,000 kg/ha to 2,050 kg/ha with a maximum of 3,500 kg/ha in Israel. In many areas of Israel, water is scarce and often has a high saline content (up to 1,200 mg cl per litre). Such water is unsuitable for agriculture but well suited for fish culture. Where fresh water is available, ponds are made deep and water is stored during the rainy season to a depth which permits operation of the ponds with very little or no addition of water during summer. When the pond is emptied, the water is not always wasted; it is re-used by emptying the water into neighbouring ponds either by gravitation or portable pumps. With this or other suitable systems water can be used more than once.

Experiments conducted some years ago in different parts of Israel proved that natural fertility of ponds can produce 200–400 kg/ha. By adding fertilizers without supplementary food, production can be raised to 800–1,000 kg/ha.

The use of specialized equipment such as cylindrical net driers, concrete catching boxes, fish graders, efficient containers with a continuous supply of air for transport of live fish, food distributors and chemical sprayers have helped to reduce production costs.

Italy

In brackish-water ponds, eels (Anguilla sp.) are raised as well as certain species of mullets (Mugil spp.), gilthead (Chryosphrys sp.) and bass (Labrax sp.). In this extensive fish culture system no artificial feeds are used. Various devices are used to regulate the salinity of water and to capture fish.

In certain areas rice fields are stocked in the spring with small one-year-old carp (Cyprinus carpio) and cropped in the autumn for marketing.

Netherlands

In 1957, scientific management of the fish farms was initiated. Within a short time, a considerable increase in the production was obtained. At the fish breeding station in Valkenswaard, the yield quadrupled as a result of fertilization, feeding and selection (1957:200 kg/ha; 1964:800 kg/ha). Considerable importance is given to the time of stocking (temperature, food production in the ponds and condition of the stocking material). Selection of carp is specially emphasized. Among other things, cross-breeding with wild carp was carried out.

Poland

Rapid progress in carp breeding started in 1870 when T. Dublisch evolved the system of transferring carp from special spawning ponds to fry ponds, and then to fingerling ponds during the first season of rearing. This system was first applied in a fish farm near Cieszyn in southern Poland. Crop rotation, i.e. alternating between cereal and fish, was known in the seventeenth century. Fertilization, first applied in the 1930's has been widely practised since about 1950. Induced spawning of carp by hypophyzation has been practised since 1948.

Romania

The most important achievements in fish culture in Romania were made by the Fish Culture Research Institute. This Institute was founded in 1940 and transformed into the Research and Fish Culture Projects Institute in 1961. From 1950 to 1965 important work has been done on:

1. fertilization to increase the trophic conditions of the ponds and thus carp production in ponds without plants or edible weeds;

2. combinations of species and the age classes for stocking and methods of fodder distribution for obtaining a gradual increase in average production of plant feeding fishes;

3. selecting carp and producing hybrids with better physiological and morphological characteristics. Artificial reproduction of carp has been developed in recent years and about 200 million fry are produced per year. New species of cyprinids have also been introduced.

Spain

In 1949, pike (Esox lucius L.) was introduced in Spain. The fish were raised in ponds and they successfully spawned at the age of one year.

To obtain a larger percentage of black bass (Micropterus salmoides) and to avoid cannibalism among the breeders, an artificial nest made of gravel and sand is placed over wooden planks or ceramic material with a cover. The embryos are then transported to the incubating tanks or ponds where the eggs hatch and the fry develop. In a similar manner, extensive culture of zooplankton (mainly Daphnia and Artemia) is carried out to feed the fry during its early stages. Those ponds are fertilized with superphosphate.

Experiments were also carried out in the culture of rainbow trout (Salmo gairdneri) and common trout (Salmo trutta) at high temperature (average monthly temperature of 26.9°C with a maximum of 29°C). ¹ The growth rates were as follows: from 5 to 23 g average weight at the age of five months, from 27 to 93 g at eight months and 110 g at 11 months.

The culture of trout in warm water is made possible by the oversaturation of oxygen of the water, with the use of aquatic plants covering 40 percent of the pond area, with abundant sunshine and shallow water.

Yugoslavia

In the last five years, important progress has been made in the culture of carp through improvements in the techniques of breeding, intensive feeding, increasing the density of stocks, artificial spawning, mechanizing the catching and transportation of fish and other techniques. As a result, production more than doubled from 500 kg/ha to 1,200 kg/ha in two years.

¹ The measure of water hardness by the determination of calcium and magnesium salts concentrations.

5 METHODS OF CULTURE

Belgium

Fish culture is carried out for the purpose of stocking natural waters and ponds. Carp, pike and eel are raised in warm-water ponds but only small quantities are intended for consumption.

There are very few installations exploited by the state and their production is used for stocking public waters. Fish culture is, generally, moderately intensive and artificial feeds and fertilizers are used.

France

Most of the fish cultured in France is consumed locally. However, in Dombes and Lorraine, production is centralized by cooperatives and most of it is exported to Germany. Fish culture is not practised in rice fields.

Carp culture in France is intensive only in about half the area of ponds where fertilizers are used with success. The practice of rotating crops (fish culture for two years and oat culture the following year) has given better results. In Dombes, this is called “évolage”.

Greece

Government fish culture establishments in Greece are exploited by private enterprise or by cooperatives under Government grants. Private enterprises and fishermen's cooperatives also practise fish culture in rice fields under natural conditions; no artificial feeds are used.

Israel

In Israel, fish culture establishments are privately owned, although very often organized as cooperative enterprises. The Government has a fish breeding station at Dor, but the station does not engage in commercial operations. Fish culture is intensive and artificial feeding as well as fertilization are adopted.

Netherlands

Apart from cold-water fish culture, commercial fish culture enterprises are of very little importance. The breeding stations are managed on a semi-government basis. Cultivation is done intensively using fertilizers and supplementary feeding when possible.

Poland

According to 1964 data, the various fish culture establishments were divided as follows as far as ownership was concerned:

Ninety percent of the fish culture carried out is intensive, using feeds, fertilizers and weed control measures.

Romania

In Romania, the trend is to use land unsuitable for agriculture for fish culture. The land area used for fish culture is increasing (now 10,000 ha or more). In the river basins and in the dammed sections of the Danube, fish culture is intensive. Production is from 1,000 to 2,000 kg/ha/year. In the delta region, fish culture is also combined with reed culture, but then fish production is not more than 150 kg/ha.

In many cases, fish culture is done in Romania by state farms. Agricultural production cooperatives also carry out fish culture but only on a small scale.

Spain

In Spain, practically all fish culture for re-stocking natural waters is governmental, but there are some fish culture establishments in the zone of “Extremadura” where tench (Tinca sp.) is cultivated in small ponds.

On 4 June 1965 the Spanish Government approved a joint development plan for agriculture and fish farming for three years (1965–1967). It should greatly stimulate development of fish culture in warm-water ponds and rice fields.

Yugoslavia

Intensive fish culture is done commercially in Yugoslavia through Government enterprises. Feeding and fertilization are done. Carp is the main species cultivated. Tench (Tinca tinca), pike-perch (Lucioperca lucioperca) and sheath fish (Silurus glanis) are also cultivated but represent only 10 percent of total production.

¹ Studies and Reviews, General Fisheries Council for the Mediterranean No. 30

6 FEEDS AND FEEDING

Belgium

Artificial feeding is practised for carp and roach (Rutilus arcasi) culture. Often corn is used and to a lesser extent, other cereals. Mixed feeds are also manufactured in granulated form for cyprinids and to a lesser extent for salmonids. Corn is imported but the other cereals and mixed feeds are produced in Belgium.

France

Artificial feeds are not used in France, except in a few cases where crushed wheat and barley are used.

Greece

Except for experimental purposes artificial feeds are not used in brackish water.

Israel

Artificial feeding is practised in carp fish farms. Fortunately, the carp is not choosy and cheap grain or second or third grade oil cakes make feeding profitable and increase yields. The feed is distributed once daily in the morning with a mechanical distributor.

The amount of feed used depends upon the fertility of the pond and the size of the fish. In well-fertilized ponds, the average food coefficient is about 1:2.5 – 3.1, that is to say that 2.5 – 3.1 kg of feed are needed to produce 1 kg of fish. This coefficient represents an average; throughout the growing season this ratio varies according to the size of the fish. A 100 g fish has a coefficient of 1:1, whereas a 500 g fish has a coefficient of 1:3.5.

The amount of feed is determined every two weeks when through fish sampling, growth rates are checked and, in accordance with the right coefficient, the final amount of food for the next two weeks is determined. Some farmers do the sampling once a week.

Feeding stops when water temperature goes below 15°C. The exact gain obtained by feeding is hard to determine, but there is good indication that of 2,000 kg of fish obtained from a hectare, about 400 kg come from the natural food of the pond, 400 more from fertilizers and an additional 1,200 from artificial feeding. These figures will probably vary for different ponds, depending on their natural fertility.

Israel has embarked recently on a research program with the aim of developing a better balanced feed with higher protein content. This is expected to give higher yields.

Netherlands

In the Netherlands, breeding stations have adopted supplementary feeding for carp. It consists mostly of grains, as a rule rye or barley, but experiments have been started with mixed feeds of various kinds of grains such as rye, wheat and barley. The average feeding for carps that are a few years old amounts to 1,600 kg of rye per ha for the period May to September inclusive. Supplementary feeding for one-year-old carp amounts to 1,100 kg of barley per ha for the period August to October inclusive.

The following results were obtained with the feeding rates given above:

Yields obtained

Feed is easily obtainable and is supplied every week. The price per 100 kg is approximately fl.31 – fl.35 ¹.

Pike fingerlings are produced in concrete basins or small ponds by feeding with live zooplankton caught in lakes or in production ponds. The system is still under development, particularly with a view to mechanization.

Poland

The main feeds used for carp in Poland are maize, sorghum and of lesser importance, rye, lupine and waste products of flour mills. The conversion factors, i.e. ratio of the amount of food to net increase in weight of stock are:

Romania

A mixture of sunflower oil cake, corn and wheat waste is used in the manufacture of artificial feeds. The conversion rates are the following: (unit weight of feed to obtain unit weight increment in fish) 3.5 kg in farms where trouts are raised for the market and 2.5 kg in farms where trouts of one summer are raised. In 1964, granulated feed was manufactured following an original recipe and the conversion rate was less than 2 kg.

Spain

The fresh-water species cultivated in warm water in Spain are the royal carp, the black-bass and the pike; all for stocking of natural waters. Tench (Tinca tinca) is raised in lagoons on a small scale for local consumption.

In carps less than one year old, the percentage of early losses is fairly high, but this percentage decreases later, more so in cases where supplementary food is used. For carps more than one year old, the mortality rate is very small, but in all cases supplementary feeds are used.

For the feeding of black bass at the fry stage, plankton cultivated in ponds is used; production of zooplankton is increased by adding superphosphate and fish meal. Black bass are fed with gambusia (Gambusia holbroockii) and roach (Rutilus arcasi) and only in certain periods, when it is difficult to find sufficient amounts of these fish, are granulated feeds used as in trout culture.

Yugoslavia

In Yugoslavia, granulated feeds, mostly corn, are used. Sometimes low quality wheat, barley, lupine etc. are also used. Previously, grains were ground and kept in water for 24 hours and then fed to the fish; lately, these artificial feeds are fed to the fish in the dry state.

The conversion rate is 2 or 3 depending mainly on the quality of the feed and the density of stocks. The cost of feed in 1964 ranged from 50 to 70 dinars¹ per kg.

¹ fl.3.64 = 1 U.S. dollar

7 FERTILIZATION

Belgium

Ponds on fish farms are often fertilized, more so if the soil is poor and fed with water having little alkaline reserve. Lime, potassium fertilizers and organic manure are used.

France

Fertilization of ponds is carried out only since about 50 years, while the drying up of the ponds and the system of rotating the crops was a traditional method inherited from the Middle Ages in certain regions (Brenne, Dombes, Forez).

The use of lime, in the form of carbonate and of agricultural lime, has contributed greatly to increasing the yields of the acid ponds of Sologne and Brenne, as well as the quality of the fish produced. Usually, 200 kg/ha of lime is used, this is usually insufficient. Certain ponds are fertilized with granulated quick lime.

The application of phosphates in ponds is well known. Phosphate slag, superphosphate and hyperphosphate are most commonly used. The quantities used are often insufficient but the positive results encourage the farmers to fertilize regularly since the end of World War I at the rate of 17 to 150 kg/ha. Potassium and nitrogenous fertilizers are seldom used in France. In 1965, trials with liquid fertilizers seemed to give satisfactory results.

Greece

Experiments in the use of fertilizers in fresh and brackish water are now under way.

Israel

Experiments in Israel have shown that fertilization enables a denser stocking rate and a better utilization of the additional feed. Experiments proved that natural fertility can produce 200–400 kg/ha of fish. By adding fertilizers without supplementary food, production can be raised to 800–1,000 kg/ha.

In most of Israel waters the nitrogen : phosphorus ratio has been found to be from 90:1 to 325:1. This means that with the supply of fresh water, a considerable amount of nitrogen is added to the pond. The other sources are the blue-green algae which is abundant in most fish ponds of the tropical regions, and which can fix considerable quantities of nitrogen from the air.

Fertilization experiments have shown that four parts of nitrogen to one part of phosphorus is the desirable ratio for good growth of plankton. In the light of these considerations, and as a result of years of experimentation in Israel, a fortnightly dose of 600 kg/ha of a 20 percent nitrogen containing fertilizer (ammonium sulphate) is recommended. Two to three weeks after filling the pond with fresh water, and in high summer (the middle of June to the middle of September) when blue-green algal blooms appear, nitrogen fertilization can be stopped.

Netherlands

Practically all the ponds in the country are fertilized yearly according to the following scheme:

Fertilization is carried out to obtain a dense growth of blue-green algae. Organic fertilizers are now increasingly used in breeding ponds. About 5 m³ chicken dung per ha is milled into the bottom to get a quick development of zooplankton. Fertilization results in 50 to 150 percent increase in production, with an average of 80 percent.

The costs of the fertilizers per 100 kg are the following:

Poland

Ammonium sulphate, ammonia liquor and superphosphate are the commonly used fertilizers. Experiments are being carried out with ammonium carbonate and urea. Organic fertilizers (manure and “green manure”) are applied to fry ponds which are used for one month only. Calcium is widely applied in ponds in Poland to improve the bottom soil, increase pH and for sanitation purposes.

Romania

Productivity varies according to the quality of the soil and water as well as the quantity and quality of artificial feeds used. In special cases, in limited areas, as much as 1,500 kg/ha/year were obtained without artificial feeding and more than 10,000 kg/ha/year with feeding. Generally, the following yields are obtained: (i) 100–150 kg/ha/year in fish-cum-reed culture without feeding; (ii) 350–500 kg/ha/year without feeding, and (iii) 1,000–2,000 kg/ha/year with feeding.

Spain

Fertilizers (superphosphate and fish meal) are used only for the production of zooplankton, especially daphnia and artemisia.

Yugoslavia

One tenth of the ponds in Yugoslavia use organic and mineral (lime, nitrogen and phosphate) fertilizers. On the average, 400 kg of phosphate are applied per hectare. When the soil is acid, 500 kg of lime per hectare are applied. Nitrogen fertilizer is used in smaller quantities than others at less than 200 kg per hectare. Small ponds, especially rearing and spawning ponds, receive organic fertilizers.

¹ 12.50 dinars = 1 U.S. dollar

8 STOCKS

Belgium

Fish culturists produce fry of carp, roach and tench in their own ponds. Pike fry are obtained from specialized fish culturists who may import fertilized eggs from abroad. Fertilized eggs or fry of pike-perch as well as eels are imported from abroad.

France

Fish culturists obtain their stocks from their own production; they do not buy them nor do they collect them from natural waters. Efforts are being made to improve the quality of carp through selection. Supply is sufficient and no new species have been introduced. In a few ponds, black bass and pike-perch are used as predators instead of pike.

Greece

Stocking of brackish-water lagoons is done naturally with fish coming from the sea or by the gathering of fry in other regions.

Israel

In Israel, fish culturists usually raise their own stocks or buy them from cooperatives that specialize in rearing fingerlings for stocking purposes. Selective improvement is practised.

Italy

Certain fish farms specialize in raising carp and tench for stocking purposes. Most of them are found in northern Italy, but two are located in central and southern Italy. Fish is sold at those establishments, but the production falls short of demand. To stock brackish-water ponds fry are caught at the mouths of canals and rivers on the coast.

Netherlands

Carp stocking material is produced in the fish culturist's own farm. Pike spawners are caught in natural public fishing waters and the eggs are fertilized artificially. Likewise, pike-perch are caught each year in public fishing waters for breeding.

Unlike pike and pike-perch, selective breeding is possible with carp. The selected system applied consists mostly in eliminating the undesirable hereditary characters. Crossbreeding is done with wild carp, which at present are tested for their utility in sport fishing.

Poland

Stocks of carp are usually obtained from pond-reared spawners. Small private farms buy fingerlings at the state farms.

Tench, pike and pike-perch stocks are mostly derived from pond-reared spawners. Abramis brama, Gardonus rutilus (Rutilus rutilus), Vimba vimba, Esox lucius, Stizostedion lucioperca stocks for stocking natural waters, are collected from nature.

Hypophthalmichthys molitrix, Ctenopharyngodon idella and Aristychthys nobilis are imported from Russia since 1964.

Rearing experiments with carp and crucian carp hybrids have been initiated.

Romania

Stocks of carps one year old, 20 to 25 days old or, more rarely, 5 to 10 days old are obtained either from rearing ponds in the fish farms or from state farms. Small carps, one summer old, are sold at eight lei ¹ a kg.

Yugoslavia

Most fish culturists raise their own stock of carp. Selection is practised in an empirical manner.

9 GOVERNMENTAL ACTIVITIES AND CONTROLS

Governmental assistance in Western European countries and Israel is usually limited to the operation of research institutes and small experimental stations. In Spain, for instance, the fish culture service has offices all over the country and each one of these has a team of technicians whose job is to solve local fish culture problems.

Limited financial assistance is given in France and Italy.

In Eastern European countries, such as Poland, Romania and Yugoslavia, governmental activities and controls in the field of inland fisheries and fish culture are many-fold. General development plans are prepared and implemented by the governments. In Yugoslavia the State finances the building of ponds through its bank and helps cooperatives in planning production. It further makes the laws and regulations concerning fish culture. In Poland regulations have been enacted to control the spread of dropsy in carps.

¹ 12 lei ≈ 1 U.S. dollar

10 PROBLEMS AND PROSPECTS

The rapid progress of industrialization has reduced the quantity and quality of water available for pond fish culture. In Poland for instance, the water deficit (and the resulting shallow ponds) has become a problem. In Italy also the supply of fresh water is limited and efforts are made for increasing the use of brackish water.

In the Netherlands and Spain there is a scarcity of stocking material. Throughout the region, spreading fish diseases have caused considerable concern. Lack of a sufficient number of qualified persons remains a widely felt handicap to fish culture development. A number of measures are being taken to solve these problems. In Israel, research programs concerning fish diseases have been intensified and a more balanced food with higher protein content is being developed. In Poland, recent measures such as the wide use of extension service at various levels has given encouraging results. Feeding, fertilizing and regulating stock density have made it possible to increase carp production from 10,000 to 15,000 tons per year.

In Yugoslavia, the 1964–70 Program for the Development of Fish Culture aims at an increase in production to 40,000 tons a year. In Romania, fish culture in the barrage zones of the Danube, in the delta and in the marsh areas of the river basin is planned to be extended to a very considerable extent.