Eight km distance from Isfahan (near Yazd-abad), on the west side of the Isfahan-Shahrekord road, there is a piece of land, the area of which is 22 hectares. This plot belongs to the Government of Iran. At present, Forest Guard Station workers are planting trees here, but 4.3 ha of this land are not yet planted with trees and the Government of Iran can allocate them for construction of a fish culture project.
The site is flat with a slight slope to the north-west. The soil is sandy and loamy. There are also shallow layers of clay which prevent filtration of soil waters
At the site of the Forest Guard Station there are underground fresh waters which are pumped from two wells to the tree plantations. The total capacity of the two pumps is 45 litres per second; it may be possible to increase the amount of pumped water by providing new wells and more pumps.
In April the temperature of the underground water was 15–18°C. These waters can be used to supply the fish cultivation ponds.
About 200–300 m east of the above-mentioned road runs a canal with fresh river water. The water temperature here depends considerably on the air temperature. The amount of water passing via the canal is quite sufficient to supply the proposed fish culture project all the year round without any detriment to the original consumers. In Isfahan the laboratory which carried out analysis of these water sources certifies that the hydrochemical characteristics of the sources are suitable for rearing fish.
The temperature of water in ponds with a weak flow or no flow at all depends on the temperature of the air, and the former determines the length of the vegetation period for the cultivated fish. Many years of meteorological observations in the Isfahan area show that the average temperature of the air varies from 4.6 to 28.5°C in different months (see Table 1).
Normally, in this area there are about 60–80 days a year when the air temperature is below zero. During 7½ months, the air temperature is stable and does not drop below 10°C. This period of time can be considered as the vegetation period for fish that will be cultivated in ponds of the fish culture project in the Isfahan area.
(a) Type of the project
Conventionally, fish that is cultivated in ponds can be divided into two groups: cold-loving species and warm-loving species. On this basis a similar division is applied to fish cultivation projects: cold-water projects and warm-water projects. The fish culture project in the Isfahan area will be a warm-water project and, consequently, the species of fish to be recommended for cultivation in ponds of this proposed establishment must be warm-loving.
(b) System of the project
Depending on the duties connected with a project, as well as on the climatic and hydrological conditions in the area and on the technical and organizational potentials, fish culture projects are divided into full-pattern and partial-pattern ones.
Partial-pattern projects can be of two kinds:
Full-pattern projects are those where fish is hatched and grown to commercial size and weight.
The plot of land allocated by the Government of Iran for fish cultivation is suitable for a full-pattern project. If such a project is established here, it will have its own breeding fish, which will provide eggs for growing of marketable fish.
(c) Production cycle of the project
The period in which the fish is grown to commercial size and weight is called the production cycle of the enterprise.
The duration of the production cycle of fish cultivation in full-pattern projects varies as it depends on climatic conditions, purposes and capabilities of the project. The duration may be one, one and a half, two and a half, or three and a half years.
It is advisable to operate the planned full-pattern fish culture project in the Isfahan area with a one and a half year production cycle. This cycle provides for growing young fish up to the age of one year. During the next vegetation period (in the Isfahan area the vegetation period is 7.5 months) the fish should gain its commercial size and weight. In the first year of the project's operation, only young fish will be grown there but in all the subsequent years young fish and market-size fish will be present.
As stated above, the proposed fish culture project in the Isfahan area will be a warm-water establishment and, naturally, the species to be cultivated there will be warm-loving ones.
Of all the valuable warm-loving species inhabiting the natural bodies of water in Iran, the common carp (Cyprinus carpio L.) deserves priority of attention. This fish easily adapts itself to the environmental conditions of ponds and grows well under these conditions. Other species of the local ichthyofauna that could be raised in fish culture projects, such as the Crucian carp (Carassius carassius L.), the tench (Tinca tinca L.) and the pike-perch (Lucioperca lucioperca L.) grow in ponds at a much slower rate than that of the average growth of common carp. It is worthwhile to note here, that the native common carp is not the best that can be cultivated in ponds. Experience of fish cultivation all over the world indicates that various forms and strains of carp, produced from the common carp as a result of selection work at pond fish culture stations, yield considerably better results.
Such pond species of fish as the leather carp and the mirror carp (also belonging to the Cyprinus carpio L.), which are widely spread in many countries, will not be popular with the Iranian consumers, due to the historically established attitude of the people to various fish. Therefore, these species cannot be recommended for cultivation in Iran.
The scale carp is the cultivated variety of the wild common carp which inhabits many natural bodies of water, including the Caspian Sea and its inflowing rivers. The breed of the scale carp was produced in the Soviet Union as a result of many years of selection at pond stations. This carp differs from its wild ancestor in that it utilizes food in a better way and consequently grows faster. The body of this fish is covered with big, closely overlapping scales; the fish, as a rule, has a silver sheen. Females obtain maturity at three to four years, males mature one year earlier. Fertility is normally 180 000 eggs per kg of the female's weight. Adult spawners (six years and more) weigh 5–7 kg or more.
The following herbivorous species can be recommended for supplementary cultivation with the scale carp: the grass carp (Ctenopharyngodon idella) and the silver carp (Hypophthalmichthys molitrix). These plant-eating species do not compete for their food either with the carp or with each other, since each of these has a certain range of diet that differs from the ranges of the other two species. Mixed cultivation of the three indicated species in a pond will considerably raise the natural fish productivity1 of the pond. A certain amount of those fish was imported into Iran from the Soviet Union. Here they soon adapted themselves to local conditions and their growth rate is high.
Sefid mahi (Rutilus frisii kutum) is a fish traditionally popular with the Iranians. This fish inhabits the Caspian Sea and migrates to spawn into the rivers of Iran and the Soviet Union. After spawning, the brood fish and the young fish of kutum come back to the sea for feeding. There are no biological techniques yet developed for the cultivation of this fish at pond stations up to the marketable size.
However, such experimental work can be undertaken at the prospective Fish Culture Project in the Isfahan area. The larvae of kutum required for this purpose could be brought from Bandar Pahlavi, where the Fisheries Research Institute is located.
The Institute's personnel can catch mature kutum spawners as they migrate to spawn into rivers, extract reproductive products, fertilize and incubate the eggs, deliver the larvae to the Isfahan Fish Culture Project and perform these experiments on growing of market-size kutum.
1 The term “natural fish productivity of a pond” is to be interpreted as the ability of the pond, during one vegetation period, to ensure a certain increase in the weight of fish inhabiting this pond, in terms of one hectare, where the fish consumes only the natural food in the pond. For example: 400 fishes, each weighing 30 g, were released in summer into a one-hectare pond. In autumn these 400 fishes were caught and they weighed 980 g each. Hence the total weight of the caught fish is 0.98 kg × 400 = 392 kg; the total weight of the planted fish was 0.03 kg × 400 = 12 kg. Consequently, the natural food resources of the pond increased the weight of the fish by 380 kg (392 - 12 = 380). This is the value of the natural fish productivity for the pond under consideration and it is expressed as 380 kg/ha. If the scale carp and the herbivorous species of fish are cultivated together, the value of the natural fish productivity for ponds in the Isfahan area project may be 600 kg/ha.
The scale carp males are kept separately from females, each in ponds specially allocated to them. At springtime, when the water temperature goes up to 18°–20°C males and females are introduced together into the spawning ponds with still water. Spawning takes place early in the morning or at sunset. Females spawn on the substrate which may be either natural grass growing in the pond or artificial (made of palm leaves, branches of coniferous trees or capron thread suspended like garlands). Artificial substrate is laid along the shores of the spawning ponds and fastened to the bed. To ensure fertilization of the maximum amount of eggs, two males are used to fertilize eggs of one female. A female spawns above the substrate and males cover the eggs with the sperm, thus fertilizing them. Eggs are sticky, so when they descend on the substrate, they attach themselves to it. After three to seven days (the period depends on the temperature of the water) larvae hatch from the eggs with small yolk sacs. For some time the hatchlings hang without any movement on the substrate, to which they attach by means of a special organ, but relatively soon they begin to move actively and feed, first on protista and wheel animalcules (Rotatoria) and then on plankton entomostracans. Five to seven days after hatching, the larvae become fry which do not differ in appearance from grown fish (they have the same morphological features). Then, this fry is to be put into rearing ponds, which must be filled with water a week before the fish is placed there. The spawning ponds are drained and the brood fish are taken back into their appropriate ponds.
The rate of planting fry into a rearing pond is calculated on the basis of the pond's natural fish productivity, percentage of fry survival during the vegetation period and of the expected weight of the fingerlings. The following formula can be used for this calculation:
where: M - the number of fry that are to be planted in spring into the rearing pond;
P - natural fish productivity of the rearing pond (kg/ha);
R - water surface area (ha);
W - the expected average weight of a fingerling in autumn (kg1);
n - yield of fingerlings in autumn, as a percentage of the survived number to that of planted fry.
In the rearing pond fry feeds on zooplankton and benthos organisms. Normally the average autumn weight of fingerlings is estimated to be 30 g. The survival rate is usually taken to be 70 percent of the number of planted fry. When the temperature of the pond water drops to 5–8°C, fingerlings lose appetite and do not grow; this goes on during the whole winter season. In the springtime when the water temperature goes up, the year-old fish (called yearlings) are transferred from the rearing pond to the finishing pond. For this purpose, the rearing pond is drained and the yearlings are counted and taken to the finishing pond. Loss of fish during the winter period does not normally exceed 20 percent of the number of planted fingerlings.
The rate of planting of yearlings into a finishing pond is calculated by the following formula:
where: M1 - the number of yearlings to be planted in spring into the finishing pond;
P - natural fish productivity of the finishing pond (kg/ha);
R - water surface area of the pond (ha);
W2 - estimated average weight of a market-size yearling+ in autumn (kg);
W1 - average weight of a yearling in spring, when it is planted into the finishing pond (kg);
n - yield of a market-size yearling+, in autumn as a percentage of the number of planted yearlings.
1 For the purposes of easy calculation the average weight of a fingerling should be converted from g into kg.
In the finishing pond, carp feed mostly on benthos organisms. In the autumn yearlings can be expected to reach commercial weight (in the Isfahan area a yearling+ will probably be 0.8 kg or more); the pond is then drained and the fish is caught and sold through the normal commercial channels. The rate of fish lost in the finishing pond does not normally exceed 10 percent of the number of yearlings planted in spring. When water is drained from the finishing pond, the pond should be dried, then the bed has to be harrowed and the pond will be filled with water only the following spring for the planting of a new batch of yearlings.
The above brief description of the biotechniques of cultivating the scale carp is valid for the extensive method of carp cultivation. This method provides for growing fish only with natural food resources of ponds, which are always limited to a certain degree and can suffice for only a certain number of fish; consequently, it restricts the yield of fish from a unit of water surface area. No matter how effectively the food resources of ponds are utilized by fish, therefore, the yield of fish will not normally be high, since it is limited by natural conditions. On the other hand, the profitability of a fish culture project greatly depends on the yield of commercial fish per unit of water surface area. To raise the harvest of fish at an extensive fish culture project, the number of fish rearing and finishing ponds should be increased or, alternatively, the existing water surface should be expanded. This alone, however, would not produce the desirable economic effect since additional capital would have to be invested into construction of new or expansion of the existing facilities. Another way of increasing the yield of pond fish without any expansion of water surface area is to introduce fertilizers and foods into ponds for the fish.
The above measures are referred to as intensification measures, and the method of project operation, where these measures are employed, is called intensive operation.
Providing feeds for fish is one of the most efficient measures to intensify the operation of a project. The reason for this is that fish will assimilate not only the diet it finds in the natural environment, but also many nutritive substances, which are not characteristic of the natural bodies of water inhabited by a given species of fish. In terms of utilization of feeds for growth, the scale carp is not inferior to cattle and is even superior. This is explained by the fact that the fish spends very little energy to keep its body temperature constant.
The underlying principle of the sharp increase in the yield of fish per unit of water surface area, is that the number of fish, planted into finishing ponds, is greatly increased (five times or more), while the percentage of fish survival and its individual growth rate remains the same as when it is cultivated only with natural food resources of the body of water.
The number of fishes to be planted into ponds with artificial food supply is calculated by the following formula:
where: A - the number of fry to be planted into rearing pond in spring;
A1 - the number of yearlings to be planted into the finishing pond in spring;
P - the natural fish productivity of the pond (kg/ha);
B - the planned increase in the fish productivity of the pond (kg/ha);
R - area of the pond's water surface (ha);
W - the planned average weight of a fingerling in autumn (kg);
W1 - average weight of a yearling in spring, when yearlings are released into the finishing pond (kg);
W2 - estimated weight of a market-size yearling+ in autumn (kg);
n - yield of fish in autumn as percentage of the number of fishes planted in spring.
To feed scale carp, various feeds of animal or vegetable origin may be used, wastes of agricultural production and of the food industry, mixed feeds, silk worm pupae, and others. This species of carp consumes even such foods poisonous to warm-blooded animals (bitter lupin, cake of coriander, castor-oil plant, tung cakes, etc.). This carp also grows well and does not have any symptoms of disease.
The index that characterized the ratio of the amount of food introduced into the pond, to the increase in fish yield, resulting from the introduction of this food, is called the feeding ratio. Foods vary in their nutritional values; consequently, their feeding ratios are different (see Table 2).
The total demand for food in the project is determined on the basis of the planned increase in the fish yield due to feeding the fish and of the feeding ratio of the food.
For example, the natural fish productivity of a pond (for scale carp) is 350 kg/ha and it is planned to increase the output of fish up to 1 750 kg/ha by feeding the fish with flax cakes, the feeding ratio of which is five. How much of these cakes will be necessary for feeding the carp in a pond of four hectares? If the increase in the fish yield per one hectare is 1 400 kg (350–1 750), for the four hectares the value will be 5 600 kg (1 400 × 4). Hence, the needed amount of flax cake to ensure the planned production of fish will be 28 000 kg (5 600 × 5).
The amount of food necessary for the whole feeding season can be calculated with the help of the following formula:
F = RPK (N-1)
where: F - the total amount of food, required for the feeding season (kg);
R - area of the pond water surface (ha);
P - the natural fish productivity of the pond (kg/ha);
K - the feeding ratio of the food;
N - the planned increase in the output of fish per hectare of the pond surface due to feeding of fish (times).
It is better to give the fish not just one kind of food, but a variety of foods mixed together. The required amounts of foods, to supply the fish with a certain food mixture, can be calculated with the help of the formula given below:
where: X - the feeding ratio of the mixture;
C, C1, … Cn - amounts of feeding components of the mixture (in weight parts);
K, K1, … Kn - feeding ratios of these components.
The quantity of food needed to satisfy the demands of the project for one month is calculated on the basis of the number of cultivated fish and its planned growth for the particular month. The tentative monthly consumption of feed in the Isfahan area is considered to be as follows (as percentage from the total consumption of the season):
The daily quantity of feed to be introduced into ponds is usually established on the basis of the tentative total consumption during the particular month, and this quantity is subject to regulation as it is consumed.
Feed is introduced into ponds twice a day: early in the morning (06.00–07.00 h) and in the second half of the day (16.00–17.00 h). Before the feed is introduced into the pond, it should be thoroughly ground and mixed with water into a thick paste. Such feed is well liked by the fish. It is even more effective to supply into the ponds granulated feeds which are better than ground feeds, since much less is lost in water, and their nutritive substances are considerably less dissolved in the water. Grains are first soaked in hot or cold water and only after this are given to the fish.
Scale carp is fed in permanent places to which it quickly becomes accustomed. For this purpose, several places, not deeper than 1–1.5 m, are chosen in every pond. It is better to put the feed not only in the bottom of the pond, but also into special feeders (i.e. wooden trays 1.5–2 m2 wide with 8–10 cm high walls). Feeders are either placed on the bottom of the pond or fixed in water at the depth of 50–80 cm (Fig. 1). Employment of such feeders makes it possible to check daily the consumption of feed by fish and if all the feed is not consumed during the day, the daily portion is reduced; on the other hand, if feeds are put directly at the bottom of the pond, such control is very difficult; the remaining feed ferments and results in a gas condition in the pond which is injurious to fish. Moreover, when feed is put into such a place, fish will not approach it and it will often be necessary to find new places for feeding.
In order to determine the required number of feeding grounds or feeding trays, it should be borne in mind that one feeding ground (tray) is established for every 2–4 000 fry (when rearing fingerlings) or every 200–400 yearlings (when rearing market-size yearlings).
The optimum temperature of water for the scale carp is 23–28°C. At the temperature of 18–20°C, carp consumes about 1.5 times less feed and if the temperature drops to about 15°C, the feed consumption decreases by three or four times. In autumn, when the water temperature is 10°C or lower, carp eats very little feed introduced into the ponds and its weight does not increase during the cold season. At that time the supply of feeds into ponds is limited and at 4°C of water temperature the supply of feeds must be stopped.
Spawners of scale carp and their recruit stock are normally raised without man-made feeds; they eat only the natural food in ponds since this type is biologically the most beneficial food. However, small amounts of feed may be introduced into ponds to supply the roughage required in their diet. The daily rate of feeds for spawners and recruit stock of the scale carp is 2–3 percent of their weight.
Grass carp and silver carp are herbivorous species. They are cultivated in ponds on every continent, except Australia. These species of fish have a high growth rate and they are excellent for growing in ponds together with the scale carp. As indicated previously, the three species do not compete with each other for food and therefore the feeding resources of ponds can be better utilized.
The grass carp and the silver carp have many common features in their reproduction. Both species attain their sexual maturity usually at the age of five or six years. In some cases, however, if they are well fed and the water temperature during the vegetation period is within 25–30°C and does not drop below 6–10°C in winter, they become mature at the age of three or four years. The spawners are 60–90 cm long and weigh from 5 to 15 kg. The average female fecundity is 500 000 eggs.
In ponds of fish culture stations the grass and silver carp do not multiply in the natural way. Spawners of these species do not spawn even in ponds with a strong flow of running water, though they develop quite normal reproductive products up to the fourth stage. Consequently, injections of pituitary gland extract are employed to stimulate maturation of their reproductive products and thus obtain a new generation of fish. Pituitary glands are usually taken from the common carp which inhabit natural bodies of water.
The process of procuring and storing the pituitary glands includes the following operations: a worker from a fish culture station goes to a fishing site, and there he takes recently caught spawners of common carp. He cuts out pieces of their brain and then removes the pituitary glands from these pieces. This is done in early spring in the pre-spawning period for the common carp, when its reproductive products are not yet cast, or in autumn. The pituitary glands of common carp are put into wide glass jars, then acetone is added to remove water and fat from the glands and the jars are closed with air-tight covers. The volume of acetone must exceed the volume of glands 15–20 times. After 24 hours the acetone is poured away and the pituitary glands are put on a sheet of paper and dried at a room temperature. Dry pituitary glands must be kept in air-tight bottles or test tubes. When it is necessary to inject spawners of grass carp and silver carp, the dry pituitary glands are taken from test tubes and ground into fine powder in a porcelain crusher, and this powder is then thoroughly mixed with a small quantity of a physiological solution (½ gramme of NaCl dissolved in 1 litre of distilled water). This suspension is injected into the back muscles of spawners by means of a syringe.
Injections of herbivorous spawners are started when the temperature in ponds is stabilized at 20°C minimum and without any considerable deviations by day or night. Females should be given two injections. For the first time, females taken from the stock pond are given an injection of maximum 2–3 mg of the pituitary substance (irrespective of the fish weight) and then they are put into an earthen live-box with running water. After 24 hours the females are taken out of the live-box and given the second injection (3–4 mg of the pituitary substance are injected per 1 kg of the fish weight), then these fishes are put into the live-box again. Males are given only one injection while females are given a second dose. Every male is given 2–3 mg of the pituitary substance. After the injection, males are put into another live-box, which is close to the live-box containing females. Reproductive products mature in males and females at the same time after about 10–16 hours, at the temperature of water at 20–22°C. Mature spawners are taken from the live-boxes and their reproductive products are removed by tightly pressing the fish body. First, eggs are taken from females and put into an enamelled vessel and then sperm is taken from the males and placed in the same vessel (2–2.5 cc of sperm is sufficient for 500 000 eggs). Then the eggs and sperm are carefully mixed and a little water is added to the mixture, so that the level of water should not be above the surface of the eggs. The process of fertilization takes 30–40 seconds after water is added; therefore, after two or three minutes it is possible to start the preparation of eggs for incubation. The fertilized eggs are thoroughly washed from the rest of the sperm and slime for five minutes and then they are placed into Weiss incubators. If the Weiss incubators are not available at the station, eggs can be incubated in a “Ses-Grin” apparatus.
The incubation period for eggs of the grass and silver carp depends on the water temperature:
|Water temperature (°C)||Incubation period for eggs (h)|
Larvae hatched from eggs are not mobile. At the water temperature of 24°C the larvae remain immobile for 35 hours. At the temperature of water equalling 24°C, larvae pass over to mixed feeding 60 hours after hatching.
Larvae are kept in live-boxes made of a material with a small mesh size (less than ½ mm). These live-boxes are put into water pools with running water or just into a rearing pond. Small-size phytoplankton and rotifers must be put into live-boxes every day. When the larvae are five to seven days old, their yolk sack disappears and their feeding becomes active and at this time the larvae are released into the rearing pond. At this stage of their growth, larvae of the grass carp and the silver carp consume minor cells of algae and young Cladocera.
On the twelfth day after hatching, silver carp larvae feed only on phytoplankton which serves as food for full-grown fish of this species. Grass carp hatchlings start feeding mostly on the zoobenthos organisms on the tenth day after hatching, and at the age of 35–40 days these larvae pass over to a vegetable diet, which is the basic food of the fish during the whole life history. However, when there is no vegetation in ponds, this species, in contrast to the silver carp, can feed on zooplankton and zoobenthos organisms and even on the feed introduced into the pond for the Cyprinus carpio. Grass carp feeds on various aquatic plants, such as: Scripus, Phragmites, Nelumbium, Iris, Typha, Sparganium, Salvinia, Spirodela, Lemna, Hydrocharis, Utricularia, Ceratophyllum, Potamogeton, Myriophyllum, Polygonum and others. Grass carp feeds quite well on ground vegetation, particularly on such crops as clover, leaves of maize, lucerne and many others. The feeding ratio of aquatic vegetation is 20–30 and that of ground vegetation is 10–15.
Provided that food is good and the thermal and hydrochemical conditions in ponds are favourable, grass carp and silver carp grow very rapidly. In the experience of the expert the weight of these species in different age groups may be as follows: fingerlings from 30 to 400 g, yearlings+ from 0.5 to 2.0 kg, two-yearlings+ from 2.5 to 4.0 kg, three-yearlings+ from 3.5 to 6 kg, four-yearlings+ from 5 to 8 kg. Similar rapid gain of weight by fish has been recorded in Iran, in the Pahlavi Bay (Mordab), where grass carp, imported from the U.S.S.R., were cultivated.
Herbivorous species of fish can be cultivated in ponds either on the basis of only the natural food resources of the ponds (the extensive type of cultivation) or on the basis of the natural food, supplemented by daily additions of vegetable feeds for grass carp and by periodic introductions of fertilizers, which greatly increase the biomass of phytoplankton, on which the silver carp feeds. The principle of calculation of the number of young plant-eating fish to be stocked in ponds, is the same as the one employed in the case of the scale carp (see formulas given earlier in this report).
To increase the biomass of phytoplankton, nitrous and phosphorous fertilizers are used, mostly ammonium nitrate and superphosphates. These fertilizers may be introduced into the ponds every fortnight during the whole vegetation period of the cultivated fish, and the dosage is varied, being subject to the water temperature. At the water temperature of 20–28°C, 75 kg of ammonium nitrate are introduced per hectare of water surface area at a time, while the amount of superphosphate is 50 kg per hectare. At lower temperatures of the water, the amount of fertilizers introduced into the ponds is reduced. Fertilizers are introduced all over the water surface of the pond to provide for homogeneous distribution of phytoplankton and the silver carp cultivated in the pond.
Calculations of a fish culture project assess the following main aspects and productivity indices; size and number of the piscicultural ponds of various categories, number of brood fish, number of fish belonging to different age groups, number of market-size fish and the required amount of feeds and fertilizers.
Taking into account the quality of water supplied by the local resources, the soil of the plot allocated for the project and the duration of the vegetation period in the area, the expert's estimates for the natural fish productivity of the ponds are 600 kg/ha (scale carp 400 kg/ha, grass carp 50 kg/ha and silver carp 150 kg/ha).
The yield of the project's market-size fish will depend on the characteristics of the finishing pond and the method of its operation (i.e. whether the extensive or intensive method will be applied).
With the total area of the plot allocated by the Government of Iran for the project equalling 4.3 ha, it will be possible to construct a 3.3 ha finishing pond.
If the extensive method is used, when the fish are sustained by the natural nutrient production, in the opinion of the expert the project's finishing pond should yield the following tentative amount of market-size fish annually:
|Scale carp||-||1 370 kg|
|Silver carp||-||520 kg|
|Grass carp||-||175 kg|
|Total||-||2 065 kg|
If the intensive fish cultivation method is used, when the number of fish is increased per hectare of water surface area by use of artificially prepared feeds and mineral fertilizers introduced into the ponds, the expert estimates that the fish yield will be increased up to five times. The expert predicts that this method should ensure an annual production of more than 3 000 kg of market-size fish per hectare of the project's finishing pond and that intensive fish cultivation will ensure the following annual production of market-size fish from the 3.3 ha finishing pond:
|Scale carp||-||6 855 kg|
|Silver carp||-||2 895 kg|
|Grass carp||-||580 kg|
|Total||-||10 330 kg|
Thus fish cultivation may be either by the extensive or intensive method.
It is clear from the calculations each female will produce a great amount of surplus fry. Due to the insufficient water surface area the project will not be able to rear all these fry in its ponds, but it will be able to introduce them into natural waters or sell them to other fisheries. However, the fry surplus does not obviate the necessity of keeping extra brood fish in the station. The project should have two female and three male scale carp and two female and two male of each of the plant-eating species. For the replacement of spawners, it will be necessary to keep a recruit stock of each cultivated species.
The extensive method of fish cultivation is not complicated as regards the techniques of rearing and propagation of fish in ponds. However, this method does not utilize the water area efficiently. The intensive method, when applied to the same water surface area, and to the same ponds, makes it possible to increase fish production by five times or even more. The number of each type of pond and the surface area of the ponds recommended for the station are given in Table 3. These ponds can be used for intensive or extensive fish culture.
In addition to the ponds, the following constructions should be built on the territory of the fish culture station:
A wooden or tarpaulin shed of 20 m2 area should be set up. Under the shed, ripe eggs and sperm will be taken from the herbivorous spawners. The eggs will be inseminated and incubated there. The shed should be equipped with a water supply system for egg incubation apparatuses. Weiss incubators are used for incubation of eggs. Normal load of a standard 7–8 litre apparatus amounts to 50 g of eggs which correspond to 50 000 eggs of grass carp or silver carp. Considering the fact that the eggs will be taken from two females each female producing 500 000 eggs, 20 incubators will be needed for incubation of 1 million eggs. Such a great number of incubators will make incubation of eggs more difficult and will result in an unnecessary consumption of water. Therefore. Weiss incubators having 35 litre capacity are recommended for the incubation of eggs. These incubators are made of plastic glass. Up to 250 000 eggs can be placed in the incubator with a water consumption of about 2–2.5 1/min. Utilization of these incubators makes it possible to cut down the number of incubators to four. The eggs taken from one female should be loaded into two incubators. If for some reason it is not possible to install a shed with a water supply, the eggs could be incubated in “Ses-Grin” apparatuses which are set in running water. The larvae hatched from the eggs should be transferred into two live-boxes installed in the rearing pond (there should be separate live-boxes for either kind of larvae).
The live-boxes are made of wooden frames covered with silk bolting cloth (mesh size smaller than 0.5 mm). The live-boxes should have the following dimensions: length - 2 m, width - 1 m, height - 1.5 m. In the live-boxes the larvae are fed with phyto - and zooplankton. When the larvae change over to active feeding (after dissolving of the yolk sacs, they are introduced into the rearing pond.
A storehouse having 50 m2 area for storage of feeds used in intensive fish cultivation should be constructed.
A 10 m2 room is required for storage of fishery implements and equipment.
A room of 20–30 m2 area is required for the personnel.
Based on the above calculations and description of ponds, the diagram of the project's ponds and production premises (Fig. 2), as well as a calendar plan of work (Table 4) have been included in the report.
If an intensive method of fish cultivation is used, the following operations should be carried out during the whole vegetation period in addition to the production processes mentioned in Table 4: daily feeding of fish (fingerlings and yearlings+) and regular introduction of fertilizers into rearing and finishing ponds. During the vegetation period the project will use 4.5–5.0 t mineral fertilizers, about 25–35 t of non-concentrated feeds and approximately 6–9 t grass feeds.
The dates of pond filling activities mentioned in Table 4 are worked out with regard to the possibility of providing the necessary amount of fresh water from a nearby canal and two wells located on the territory of the Forest Guard Station (Table 5). In the process of the ponds' operation, these resources of water will be capable of supplying primary consumers daily with the necessary amount of water since the total water consumption of the project will be low.
If the extensive method of fish cultivation is used at the Isfahan project, the services of two persons will be necessary: a skilled fish culturist and a worker. In case the intensive method is applied, the project will need a staff of three persons: one skilled fish culturist and two workers.
A skilled fish culturist can be trained at three-month courses at the Fisheries Research Institute, Bandar Pahlavi.
Choosing the fish cultivation method (i.e. extensive or intensive method) is to a great extent conditioned by economics.
In the expert's opinion the intensive method of fish cultivation is the method which is economically feasible and financially stable. If the extensive method of cultivation is applied, the project will not be feasible and the investments will not be justified.
Proceeding from the above considerations, it is advisable for the Fish Culture Project in the Isfahan area to adopt the intensive method of fish culture.
On the Forest Guard Station territory located at eight km distance from Isfahan (near Yazd-abad, on the western side of Isfahan-Shahrekord road) there is a vacant plot of 4.3 ha area suitable for construction of a warm-water full-pattern fish culture station with a 1½ year production cycle.
The underground waters and the canal where river water is flowing can be used as a source of water-supply for the project.
Species for cultivation in the project could be recommended as follows: scale carp, grass carp and silver carp.
It is advisable to choose the intensive method of fish cultivation.
If the intensive method of fish cultivation is used, the yield of market-size fish will possibly be in the order of 3 t per ha of the finishing pond area.
The project's service personnel should consist of three persons.
The skilled fish culturist required for the project could be trained at a three-month course at the Fisheries Research Institute, Bandar Pahlavi.
There are vast tracts of rice fields in Iran. These rice fields are peculiar shallow reservoirs which, after appropriate modification, can be used not only for rice cultivation but also for production of fish as a by-product, particularly market-size common carp and silver carp. In that case, rice crop capacity of the fields increases due to the fact that carp exterminate some rice pests, such as “rice mosquito”, and eat the seed of some weeds. In search of food, carp dig into the bottom and loosen the soil thus contributing to its aeration without destroying paddy roots and stems. Besides, to a certain extent, the fish fertilize soil of rice fields with excrement and, by eating the larvae of the anopheline mosquito in great quantities, contribute to the sanitation of the surrounding countryside.
Modification of rice fields for fish cultivation is comparatively simple work comprising appropriate reconstruction of the fields' bottom, installation of devices preventing fish from escaping (gratings or wattles) on water inlets and outlets, as well as reinforcement of the earthen bunds which divide the fields. Along the bunds' inner side, small ditches of 40–50 cm width and 30–40 cm depth should be dug out. When the rice fields are temporarily drained, fish concentrate in these ditches. In such periods, the ditches are constantly supplied with fresh water. Sometimes, in order to preserve the fish during temporary draining of rice fields, special earthen pools having 0.5–0.6 m depth and an area of several square metres are constructed.
It is possible to establish finishing fish culture stations with a one-summer production cycle on the rice fields of Iran. Market-size yearlings+ of common carp and silver carp can be raised in such stations. Every spring, yearlings of these species should be transported from fish hatcheries, which might be set up on village reservoirs supplying rice fields with water, and released into the rice fields.
Natural fish productivity of the rice fields equals 50–60 kg/ha and 100–200 kg/ha as regards silver carp and common carp respectively. Mortality rate of these species yearlings+ during the period of their growth will amount to 20–30 percent of released yearlings+ total number.
In order to increase fish productivity of the rice fields, the following techniques of intensified fish cultivation can be applied: the number of fish released for growing per unit of a rice field's water surface area should be doubled or trebled as compared with so-called normal release rates adopted at the extensive method of fish cultivation; measures to fertilize rice fields and feed the carp with locally available feeds (rice bran, cake, powdered dry pupae of silk worm and other feeds) should be taken.
Stocking of rice fields is calculated on the same basis as stocking of conventional piscicultural ponds, i.e. it is necessary to take into account fish productivity of the rice fields, the fields' actual water surface area, initial body weight of the fish released for growing, body weight to be obtained at the end of the vegetation period and, finally, the fish mortality rate during the period of its growth.
It is possible to establish fish culture stations with a one-summer production cycle, on the rice fields of northern Iran.
Common carp and silver carp can be chosen as possible objects of market-size fish rearing in these stations.
In the expert's opinion the productivity of the rice fields will amount to 150–250 kg of fish per hectare, and if the intensification method is applied, fish yield of the same rice fields will increase.
In order to provide the fish culture stations with yearlings, it will be necessary to construct fish hatcheries on village reservoirs supplying the rice fields with water.
The use of herbicides and pesticides must be rigorously controlled and limited when the rice fields are used for fish culture.
In the Caspian plains (northern provinces of Iran) there are great numbers of village reservoirs. For example, the provinces of Mazandaran and Guilan have about 120 reservoirs.1
Most of the reservoirs are artificial. Located near villages, they are pieces of land surrounded with bunds and filled with the water of near-by rivers. An area of a village reservoir ranges from 10 up to 300–400 ha. Their maximum depth is 2–3 m and their average depth equals 1.5 m. These reservoirs may be drained, should the need arise. Water surface of some reservoirs does not have any coarse emergent plants, while in other reservoirs the water surface is covered with such plants completely or partly.
Village reservoirs have been constructed for the purpose of storing a volume of water sufficient for the irrigation of agricultural areas, mostly rice fields. The reservoirs overgrown with thick coarse emergent plants serve as wintering areas for the birds of passage; some indigenous birds dwell there permanently.
1 Since many reservoirs have never been registered, their total area is unknown at present. Some villages have ponds of 1–2 ha area.
In addition to their original purpose mentioned above, many reservoirs where the coarse emergent plants either do not exist, or are sparse and occupy small areas, can be used for organization of finishing fish culture stations with a one-summer production cycle. At present, common carp (Cyprinus carpio L.) and pike (Esox lucius L.) inhabit such reservoirs. However, the number of these fishes is insignificant and of no particular interest for commercial fishing. Once established on the village reservoirs, fish culture stations with one-summer production cycles will be successful provided that fish hatcheries are constructed. In the opinion of the expert yearlings of 20–30 g body weight released into a village reservoir in spring should grow to 0.5–1.0 kg in autumn of the same year.
By now, it is possible to locate two hatchery sites in the Mazandaran province as well as species and a number of young fish to be raised there. One fish hatchery should be constructed on two reservoirs of Lapoo (vicinity of Zaghmars) having a total area of 100 ha. Another hatchery could be established near the village of Mollakala (vicinity of Feridoun-Kenar). This village has three reservoirs of 10 ha area each. A second hatchery could supply young fish also for the 40 ha Alamdeh reservoir located near Sari-Rasht highway (two kilometres from Mollakala village). The total area of the four reservoirs which will receive young fish from this hatchery amounts to 70 ha.
The species and number of young fish most expedient for growing in the hatcheries mentioned above are given in Table 7.
The fish hatchery at Mollakala village could annually supply young fish to four village reservoirs existing there and having a total area of 70 ha (three reservoirs, 10 ha each, are situated near the village proper, while the fourth reservoir called Alamdeh, 40 ha area, is located by the roadside of Sari-Rasht highway, at a 2 km distance from the village). Construction of the hatchery will make it possible to rear annually market-size fish in the reservoirs mentioned above.
The species to be reared in the hatchery might be the following: scale carp, silver carp and pike-perch.
The fish hatchery's total area will be about 4 ha. On this plot the following ponds and premises should be constructed:
1 The pike-perch spawners are not to be kept in the hatchery permanently. They should be caught annually during this species' pre-spawning period in estuaries or in the coastal area of the Caspian Sea and brought to the hatchery for spawning.
The fish hatchery can be constructed on the plot adjoining the upper reservoir of Mollakala village. The soil is podzol there and contains very small amounts of mineral substances. The water needed for the fish hatchery can be supplied from the Serkh-Rud River. Hydrochemical characteristics of this river's water are quite favourable for propagation of the species mentioned above.
The diagram of the fish hatchery's ponds and premises' layout is shown on Fig. 5.
The main technical requirements to be met during construction of the hatchery's ponds of various categories and the room for silver carp eggs' incubation have already been described in “Biological Grounds for Designing a Fish Culture Project in the Isfahan Area” (Table 3). The only departure from these requirements will be characteristics of the pond for the pike-perch spawning which should be 1.5–2.5 m deep. In other words, this pond should be considerably deeper than that for spawning of the scale carp.
All the ponds of the hatchery should have properly designed beds in order to ensure their complete drainage. Water supply and drainage devices should be installed there. The scale carp spawning pond's bed as well as the dikes' slopes should be thickly sown with soft submerged aquatic vegetation. The pike-perch spawning pond should have natural substrate which this species sheds its eggs on. In case it is impossible to create natural substrate in the pond, artificial spawning nests made of small frames having 0.5 × 0.5 m dimensions should be used there. Thoroughly washed thin roots of willow, bulrush or garlands made of nylon threads should be laid on the frames.
During construction of ponds of all categories, particular emphasis should be placed upon prevention of seepage through the ponds' dikes and beds. Every pond should have independent water supply and drainage systems. The season of main water consumption will be spring when the ponds are to be filled. During filling of the rearing ponds, for some 4–8 days, the water consumption rate will reach its maximal level, i.e. about 45 l/sec.
The fish hatchery will raise annually yearlings of scale carp, silver carp and pike-perch in numbers required for stocking of the above-mentioned village reservoirs with the aim of producing marketable fish. To rear the needed number of yearlings, the hatchery should be provided with a certain amount of spawners, recruit-stock, larvae, fry and fingerlings (see Table 11). In the expert's opinion the value of natural fish productivity of the rearing pond for the young pike-perch will amount to 120 kg/ha, and if the method of mixed breeding of young scale carp and silver carp is used, the natural fish productivity of the pond will be 350 kg/ha and 170 kg/ha respectively.
The techniques of cultivation and rearing of scale and silver carps have been described in detail in “Biological Grounds for Designing a Fish Culture Project in the Isfahan Area”. If intensive method of young scale carp cultivation is used, the fish hatchery will require some 14 t of artificial feeds. The amount of mineral fertilizers to be introduced into the pond during intensive rearing of young silver carp will equal 4–6 t.
So far as the pike-perch propagation and rearing techniques are concerned, they are described below:
In the spring, during pre-spawning period (in March) a fish culturist makes a trip to fish catching stations (in Iran such stations are located on the Caspian Sea coast) and selects from the catches the required number of mature pike-perch spawners, their size being not less than 40–50 cm. Then the selected brood fish are transported by truck to the fish hatchery where they are released into the spawning pond. The pike-perch spawns at water temperature ranging from 8–15°C to 20°C. The pike-perch does not necessarily require running water in the spawning pond. However, the dissolved oxygen concentration value should not be less than 4–5 mg/l. Sometimes, in order to accelerate the process of spawning, the pike-perch spawners are injected with pituitary gland suspension (a female is injected with 2 mg of dried pituitary substance and a male with 1 mg of the substance). After 3 to 10 days (which depends on water temperature) free embryos hatch from the eggs shed by the pike-perch. In 2–4 days, the free embryos begin to swim actively in the water. In this period they start mixed and then active feeding thus metamorphosing into larvae. Subsequently, the larvae are transferred from the spawning pond into the rearing pond. The larval stage lasts for about 15 to 25 days depending on the water temperature. By the end of this period, the young pike-perch attain 14 to 18 mm body length. At this stage their primary food is zooplankton. A 19–20 mm long young pike-perch is able to feed on fish larvae and fry, but if it cannot find them it readily consumes invertebrates as well, i.e. low crustaceans, larvae of Chironomidae and other insects provided that their size is appropriate for consumption. When the young pike-perch gain 0.5 to 1.0 g weight, it is advisable to start adding small-size coarse fish to its food. As a result of such practice, normal development and growth of the young pike-perch will be ensured and possible cannibalism prevented. Some 300 to 400 kg of small-size coarse fish will be needed for the whole period of raising pike-perch yearlings. Regular transportation of the required amount of coarse fish to the hatchery will not present difficulties since in the Mazandaran province located on the Caspian coast they have great potentialities in this respect.
The fish hatchery's successful performance will, to a great extent, depend on keeping the calendar schedule of work on every stage of the production process. The following Calendar Plan of the Fish Hatchery's Work is suggested (see Table 7).
All village reservoirs existing in the Caspian plains area should be surveyed with the purpose of assessing their respective areas, depths, extent to which the reservoirs are overgrown with coarse emergent plants, sources of water supply, thermal and hydrochemical conditions, fish foods and presence or lack of ichthyofauna.
Once the reservoirs are surveyed, it will be necessary to choose the reservoirs which could be used for cultivation of market-size fish without considerable capital investments. In this case, the species which can be raised in a particular reservoir, as well as its estimated natural fish productivity, should be indicated.
In order to ensure an annual supply of yearlings to the market-size fish rearing stations which can be set up on the reservoirs chosen for this purpose, fish hatcheries should be constructed. The species and number of young fish to be raised in a hatchery should be determined on the basis of specific requirements of the fish culture stations.
Suggestions for the construction of fish hatcheries in Lapoo and Mollakala, Mazandaran province, which were made in the report may serve as a guideline for choosing a fish hatchery site as well as the species and number of fish to be raised there. These two hatcheries will supply six reservoirs having a total area of 170 ha with young fish. In the opinion of the expert market-size fish yield of the reservoirs will amount to 100 t of fish in case extensive method of fish cultivation is implemented and about 390 t of fish if the intensive method is applied.
In order to make fish cultivation in the provinces of Mazandaran and Guilan successful it will be necessary to train fish culturists at training courses, the Fisheries Research Institute, Bandar Pahlavi, choosing students from inhabitants of the villages with reservoirs to be used for rearing of market-size fish.