Anisimova I.M., Lavrovsky V.V. Ichthyology. The structure and some physiological features of fish. excretory system and osmoregulation. Physiology and ecology of fish Fish and environment
Passing fish. Widespread off the coast of Europe. Mediterranean coast from Gibraltar to Scandinavia, in the western part of the Baltic Sea, including the coast of the Kaliningrad region (Svetovidov, 1973; Hoestlandt, 1991). Rarely found in Russian waters. There are no subspecies. The taxon originally described as Alosa alosa bulgarica from the southwestern Black Sea (Svetovidov, 1952) is now considered A. caspia bulgarica (Marinov, 1964; Svetovidov, 1973). The Macedonian subspecies A. alosa macedónica (Svetovidov, 1973) is now recognized as an independent species Alosa macedónica Vinciguerra, 1921 (Economidis, 1974; Hoestlandt, 1991). Included in the IUCN Red List. It is an object of fishing.[ ...]
Anadromous fish, unlike non-anadromous ones, should be able to easily switch from the "freshwater" method of osmo-regulation to the "marine" one when moving from fresh water to sea water, and vice versa, when moving in the opposite direction.[ ...]
Anadromous fish dramatically change their habitat (marine to freshwater and vice versa), travel great distances (salmon travel 1100-2500 km at a speed of 50-100 km per day), overcome significant rapids, waterfalls.[ ...]
Passing fish. They move for spawning (spawning) either from sea water to fresh water (salmon, herring, sturgeon), or from fresh water to sea water (eels, etc.).[ ...]
Anadromous and freshwater species. It lives in the basins of the Barents, White, Baltic, Black, Caspian and Aral seas. 6 subspecies were noted, of which 4 anadromous and 1 lacustrine live in the waters of Russia. Anadromous fish of Northern Europe, in Russia in the basins of the Baltic, White and Barents Seas up to the Pechora. Freshwater river (trout) and lake (trout) forms are widespread throughout the basins of these seas. Object of fishing and fish farming. The Baltic populations are sharply reducing their numbers. Scheduled for inclusion in the "Red Book of Russia".[ ...]
Anadromous fish of the salmon family. In adulthood, it reaches a length of up to 60 cm and a weight of up to 6 kg. It lives off the coast of the Far Eastern seas. It spawns in the rivers of Japan and the Kuril Islands, Primorye and Sakhalin. It is an important fishery object.[ ...]
Anadromous fish of the Black and Azov Seas. Enters rivers (Don, Dnieper, Danube Delta). The species and its intraspecific forms require additional research. Benarescu (Bänärescu, 1964) distinguishes two subspecies from the north-central part of the Black Sea: A. p. borystenis Pavlov, 1954 and A. p. issattschenkov Pavlov, 1959, but does not describe them. Valuable commercial species. Included in the IUCN Red List under category DD (IUCN Red list..., 1996).[ ...]
In anadromous fish moving for spawning from rivers to seas and vice versa, the osmotic pressure undergoes changes, albeit insignificant ones. During the transition from sea water to fresh water, these fish almost completely stop the flow of water into the body through the intestines as a result of degeneration of its mucous membranes (see below, the chapter on migrations).[ ...]
Many anadromous fish and cyclostomes feed in the sea, and enter rivers for breeding, making anadromous migrations. Anadromous migrations are characteristic of lampreys, sturgeons, salmons, some herrings, cyprinids, and others.
Salmon is a migratory fish. Juveniles live in fresh water from 2 to 5 years, eat insects, then slide into the sea and become predatory fish. The usual place for salmon fattening is the Baltic Sea. Some juveniles remain in the Gulf of Bothnia and the Gulf of Finland. For example, in the Soviet Union, artificially bred salmon does not leave the waters of the Gulf of Finland. For two years in the sea salmon reaches 3-5 kg weight. It feeds mainly on herring, sprat, and gerbil. Having reached puberty, the salmon goes to the river where he was born. The river, the place of his spawning, he finds by the smell of water.[ ...]
Berg L.S. Fish of the USSR and neighboring countries. Berg L.S. Spring and winter races in anadromous fishes, "Essays on General Issues of Ichthyology". Iad-vo AN SSSR, 1953, p. 242-260.[ ...]
Lamprey is an anadromous fish, found in the lower Volga and in the channels of the delta, even in its coastal part. Currently very few. Leads a hidden lifestyle. It spawns from March to May in strong currents in places with rocky or sandy shoals or in pits. The first larvae appear in May. Like adults, they lead a hidden lifestyle, burrowing into silt or sand. Caught very rarely.[ ...]
The movement of migratory fish, mainly of the Northern Hemisphere (salmon, sturgeon, etc.) from the seas to the rivers for spawning.[ ...]
L. S. Berg. Fishes of fresh waters of Russia. C. 2 p. II and d. Define tables of marine and anadromous fishes of Europe.[ ...]
Sevruga is an anadromous fish that lives in the basins of the Caspian, Azov and Black Seas. For spawning, it goes to the Ural, Volga, Kura and other rivers. This is a numerous valuable commercial fish, reaching a length of about 2.2 m and a weight of 6-8 kg (average commercial weight is 7-8 kg). Female stellate sturgeon reach puberty at 12-17 years old, males - at 9-12 years old. The fertility of females is 20-400 thousand eggs. Spawning takes place from May to August. The duration of incubation of eggs at 23 °C is about 2-3 days. Juveniles slide into the sea at the age of 2-3 months.[ ...]
Caspian anadromous fish spawn in the rivers Volga, Ural, Kure. But the Volga and the Kura are regulated by cascades of hydropower plants, and many spawning grounds turned out to be inaccessible to fish. Only the lower reaches of the river The Urals were left free from the construction of hydroelectric facilities to preserve the spawning migrations of fish and their natural reproduction. Currently, the reduction in the natural reproduction of fish products is partially offset by artificial fish farming.[ ...]
Commercial fish of the sturgeon family, common in the basins of the Aral, Caspian and Black Seas. A thorn is an anadromous fish, it enters rivers for spawning, there are also “residential” forms of a thorn” that do not leave the rivers for several years, “probably” before puberty.[ ...]
Most fish usually stop feeding during river migration or feed less intensively than in the sea, and the huge expenditure of energy, of course, requires the consumption of nutrients accumulated during feeding in the sea. This is why most anadromous fish experience severe depletion as they move up the river.[ ...]
As a rule, fish have permanent places of feeding (“fatting”). Some fish constantly live, breed and winter in areas rich in food, others make significant movements to feeding grounds (feeding migrations), spawning (spawning migrations) or wintering grounds (wintering migrations). In accordance with this, fish are divided into sedentary (or non-aquatic), anadromous and semi-anadromous. Anadromous fish make long journeys either from the seas, where they spend most of their lives, to spawning grounds in rivers (chum salmon, salmon, white salmon, nelma), or from the rivers in which they live, go to the sea (eel). [ . ..]
However, the presence of anadromous fish in the subtropics, tropics, and the equatorial zone indicates that desalination alone was not the cause of the emergence of anadromous lifestyle. The transition of marine or river fishes to anadromous way of life could develop even with a relatively stable flow regime of rivers, into which anadromous fish enter for reproduction.[ ...]
For the protection of a number of migratory fish, hatcheries are of great importance. At such plants, usually built at the mouths of large rivers or near dams, producers are caught and artificial insemination is carried out. The larvae of fish obtained from caviar are kept in rearing ponds, and then the grown juveniles are released into rivers or reservoirs. In Russia, billions of juveniles are grown annually in such farms, which is of great importance in the reproduction and restoration of valuable fish species: sturgeon, salmon, some whitefish and other anadromous and some semi-anadromous fish, such as zander.[ ...]
In addition to these institutes, basin research institutes of fisheries conduct research in each fishery basin. Research in inland waters is carried out by the All-Union Research Institute of Pond Fisheries (VNIYPRH), which is part of the All-Union Research and Production Association for Fish Farming (VNPO for Fish Farming), UkrNIIRKh and other scientific organizations in many Union republics.[ ...]
Kutum (Rutilus frissi kutum Kamensky) is an anadromous fish of the southwestern region of the Caspian basin. Acclimatized in the basin of the Black and Azov seas. A related form - carp (R. frissi Nordm.) was known in the rivers of the northwestern part of the Black Sea, currently found only in the river. Southern Bug.[ ...]
Mass tagging and tracking of fish carrying ultrasonic transmitters showed that both the lower and upper spawning grounds are used by spawners of the same local herd, who do not go beyond its range during the feeding and wintering period. The spawning grounds are approached either in autumn (winter fish) or in spring (spring fish). The stereotype of behavior of spawners going to spawn in the river does not differ from that described for typically migratory fish.[ ...]
Wintering migrations are expressed both in anadromous and semi-anadromous, and in marine and freshwater fish. In anadromous fish, wintering migration is often, as it were, the beginning of spawning. Winter forms of anadromous fish move from feeding areas in the sea to wintering in rivers, where they concentrate in deep holes and hibernate in a sedentary state, usually not feeding. Wintering migrations take place among anadromous fish in sturgeon, Atlantic salmon, Aral barbel and some others. Wintering migrations are well expressed in many semi-anadromous fishes. In the Northern Caspian, the Aral and Azov Seas, adult roach, ram, bream, pike perch and some other semi-anadromous fish after the end of the feeding period move to the lower reaches of the rivers to wintering places.[ ...]
The decrease in the stocks of some commercial fish (salmon, sturgeon, herring, some cyprinids, etc.) and especially the change in the hydrological regime of large rivers (Volga, Kura, Dnieper, etc.) force researchers to intensively deal with questions of fish reproduction. Hydraulic construction on the rivers causes such great disturbance of their regimes that many migratory fish cannot use the old spawning grounds in the rivers. The lack of proper external conditions excludes the reproduction of migratory fish.[ ...]
At the same time, acclimatized fish species appeared: sabrefish, white-eye, carp, silver carp, rotan, eel, guppies, etc. Now the ichthyofauna of the river. Moscow has 37 species (Sokolov et al., 2000). Anadromous fish have completely disappeared, as well as fish species that need conditions in fast-flowing rivers. More numerous are fish resistant to eutrophication - inhabitants of stagnant or slow-flowing waters.[ ...]
The main objects of breeding at fish hatcheries were migratory fish: sturgeon, salmon, whitefish, cyprinids. In spawning and rearing farms and fish hatcheries, semi-anadromous and non-migratory fish are bred: carp, perch, etc.[ ...]
The most important method of increasing the productivity of commercial fish stocks is to catch fish when it is in the most commercially valuable condition. For most fish, their fat content and fatness varies greatly with the seasons. This is especially pronounced in anadromous fish that make large migrations without food consumption, as well as in fish that have a break in feeding during wintering.[ ...]
In our country, work on the acclimatization of fish is being widely developed. The incentive for such activities is the growing need for the production of commercial fish. For the purpose of acclimatization, the ichthyofauna of some water bodies (Lakes Sevan, Balkhash, the Aral Sea) is reconstructed by introducing valuable fish species, the newly created water bodies (reservoirs) are populated with new fish species, etc. slow flow. We are convinced that almost all anadromous fish (living in sea and fresh water) can be transferred to fresh water - in ponds.[ ...]
Anadromous fish - herring, salmon, sturgeon, carp annually rush hundreds and thousands of kilometers up the river.[ ...]
The fourth type of migration cycles is characteristic of a number of local populations of migratory fish from lakes and reservoirs that have developed reproductive biotopes in rivers flowing from a feeding reservoir. These fish make pre-spawning migration downstream of the river, and after spawning they return to lake feeding biotopes, where they live until the next spawning period. In local herds, groups of winter individuals were also found here, leaving for the spawning area in autumn, i.e., performing wintering and spawning migration.[ ...]
All salmonids, both those belonging to the genus Salmo and those belonging to the genus Oncorhynchus, are fish that spawn in autumn (see the Gogchin trout above for an exception). None of them breeds in sea water-; for spawning, all salmon enter the rivers: even a small amount of green water is deadly for spermatozoa and for eggs, thus preventing the possibility of their fertilization. Some of the salmon - salmon, anadromous trout, Salmo trutta L. and the Caspian and Aral salmon and all Far Eastern salmon - are typical migratory fish living in the marine environment and only for breeding purposes entering the rivers, others - lake salmon (Salmo trutta lacustris) , the brook forms of Salmo trutta and its subspecies, which form trout morphs, are non-aquatic and live all the time in a fresh environment, only making small movements from feeding places to spawning places. In some cases, typical anadromous fish also form or have formed in the past forms that permanently live in fresh water. To which belong: Salmo salar morpha relictus (Malmgren) - lake salmon, lake forms of Oncorhynchus nerka, river form of Salmo (Oncorhynchus) masu. All of these freshwater morphs differ from their marine relatives in their smaller size and slower growth rate. This is already the effect of fresh water, as we will see below, and on typical migratory salmon, since they have to live in fresh water.[ ...]
The adaptive value of dwarf, permanently living in rivers, males in anadromous fish is to provide a population of larger numbers and greater reproductive capacity with a smaller food supply than if the males were large, anadromous.[ ...]
The physiological features of the migratory state are best studied in anadromous fish using the example of (Jishdromous spawning migrations. In these fish, as well as in lampreys, the stimulus for spawning migration occurs after a long (from 1 to 15-16 years) period of marine life. Migratory behavior can be formed in different seasons and different conditions of the reproductive system.An example is the so-called spring and winter races of fish and cyclostomes.The most common indicator that stimulates migration in fish is high fat content.As you approach spawning grounds, fat reserves decrease, which reflects the high level of energy expenditure on the movement and maturation of reproductive products.And in this case, there are differences between spring and winter races: in spring, entering the rivers in the spring, shortly before spawning, the fat content is not very high.[ ...]
A sub-variant of type III migrations are displacements. winter ecological groups of local migratory fish stocks” breeding in spring, but entering the rivers in areas of reproductive biotopes in the autumn of the previous year.[ ...]
The method is also widespread, when spawning of commercial fish occurs in artificial reservoirs, juveniles grow up to the stage of the stingray and then are released into natural reservoirs. In this way, artificial reproduction of semi-anadromous commercial fish - bream, carp, etc. is built in fish farms of the Volga delta, the lower reaches of the Don, the Kuban and a number of other rivers. Also an important form of fish farming is one in which a person leads the whole process from the moment of obtaining mature productive caviar and milk from producers, fertilization of caviar, its incubation to the release of viable juveniles from a fish hatchery into a natural reservoir. Thus, breeding is carried out mainly of migratory fish - sturgeons, for example, on the Kura, salmon in the north and the Far East, whitefish and some others (Cherfas, 1956). With this type of breeding, it is often necessary to keep the producers until the maturation of their reproductive products, and sometimes stimulate the return of the reproductive products by injecting the pituitary hormone. Caviar incubation is carried out in special fish-breeding devices installed in a special room or exposed in the riverbed. Juveniles are usually grown up to a sloping state in special pools or ponds. At the same time, juveniles are fed with artificial or natural feed. Many fish hatcheries have special workshops for growing live food - crustaceans, low-bristle worms, and bloodworms. The efficiency of a fish hatchery is determined by the vitality of the juveniles released from the hatchery, i.e., by the value of the commercial return. Naturally, the higher the applied fish farming biotechnology, the higher it is. efficiency.[ ...]
The first step towards resolving this issue is the delay in the duration of the freshwater lifestyle of anadromous fish. With regard to sturgeons (sturgeon, stellate sturgeon and beluga), this is already being successfully implemented. The second and most difficult stage is the management of the reproduction process.[ ...]
Daily food intake also depends on age: juveniles usually eat more than adults and old fish. In the pre-spawning period, the intensity of feeding decreases, and many marine and especially migratory fish feed little or completely stop feeding. The daily rhythm of feeding also differs in different fish. For peaceful fish, especially plankton-eating ones, breaks in feeding are small, and for predatory ones they can last more than a day. In cyprinids, two maximums of feeding activity are noted: in the morning and in the evening.[ ...]
In the same region, the entire life cycle of vendace and smelt passes, which, in their migrations, with the exception of 4 Tsuchyerechenskaya, do not go beyond the delta. Their spawning takes place in tundra rivers connected with bays and river deltas. Part of the vendace spawns directly in the bays of the bay (New Port area). Of the other fish, ruff and burbot deserve attention, the stocks of which are underused.[ ...]
Undoubtedly, the temperature regime is the leading factor determining the normal course of maturation of the gametes of fish, the onset and duration of spawning, and its effectiveness. However, under natural conditions, for the successful reproduction of most freshwater and anadromous fish, the hydrological regime, or rather, the optimal combination of temperature and level regimes of the reservoir, is also important. It is known that the spawning of many fish begins with an intensive rise in water and, as a rule, coincides with the peak of the flood. Meanwhile, the regulation of the flow of many rivers has drastically changed their hydrological regime and the usual ecological conditions for the reproduction of fish, both those that are forced to live in the reservoirs themselves, and those that remain in the downstream of the waterworks.[ ...]
It should be noted that the herds or ecological races into which a subspecies breaks up often have different breeding grounds. In semi-anadromous and anadromous fish, so-called seasonal races and biological groups are also formed, which have a similar biological significance. But in this case (for herds and races) the "order" of reproduction is provided even more by the fact that it is fixed hereditarily.[ ...]
An almost extinct species, previously widespread along the entire coast of Europe (Berg, 1948; Holöik, 1989). In the north met up to Murman (Lagunov, Konstantinov, 1954). Passing fish. In Lakes Ladoga and Onega, there may have been a resident form (Berg, 1948; Pillow, 1985; Kudersky, 1983). A very valuable species, which had a commercial value in the late XIX - early XX centuries. It is included in the "Red Books" of the IUCN, the USSR, among the specially protected fish of Europe (Pavlov et al., 1994) and is scheduled for inclusion in the "Red Book of Russia".[ ...]
The impact of hydropower on the conditions for the reproduction of fish stocks is one of the most actively discussed issues in the environmental problem. The annual fish production in the former USSR reached 10 million tons, of which about 90% was caught in the open seas, and only 10% of the catch belongs to the inland basins. But in the inland seas, rivers, lakes and reservoirs, about 90% of the world's stocks of the most valuable fish species - sturgeon and more than 60% - salmon are reproduced, which makes inland water bodies of particular importance in the country for fish farming. The negative impact of hydraulic structures of hydroelectric power plants on fisheries is manifested in violation of the natural migration routes of migratory fish (sturgeon, salmon, whitefish) to spawning grounds and a sharp decrease in flood water flow, which does not provide watering of spawning grounds of semi-anadromous fish in the lower reaches of rivers (carp, pike perch, bream) . The reduction of fish stocks in inland waters is also influenced by pollution of water basins with discharges of oil products and effluents from industrial enterprises, timber rafting, water transport, discharges of fertilizers and chemical pest control agents.[ ...]
First of all, due to the elementary populations, a heterogeneous quality of the population of a given herd arises. Imagine that, for example, vobla in the Northern Caspian or other semi-anadromous or migratory fish would not have such heterogeneous quality, and, say, all fish would mature at the same time and therefore all would immediately rush to the Volga delta to spawn. In this case, there would be overpopulation at the spawning grounds and the death of producers due to lack of oxygen. But there is no such overpopulation and cannot be, since in reality the spawning run is quite extended and the fish can alternately use limited breeding grounds, ensuring the continuation of the life of a given subspecies or herd.[ ...]
Pasture fish farming has large reserves, based on obtaining marketable products by improving and productively using the natural food base of lakes, rivers, reservoirs, fish acclimatization and the directed formation of the ichthyofauna, artificial breeding and rearing of juvenile anadromous fish (sturgeon, salmon) to restore their stocks. [...]
Intensive human activity associated with the development of industry, agriculture, water transport, etc., in a number of cases had a negative impact on the state of fishery reservoirs. Almost all the largest rivers in our country: the Volga, Kama, Ural, Don, Kuban, Dnieper, Dniester, Daugava, Angara, Yenisei, Irtysh, Syr Darya, Amu Darya, Kura, etc. are partially or completely regulated by the dams of large hydroelectric power stations or irrigation hydroelectric facilities. Almost all anadromous fish - sturgeon, salmon, whitefish, carp, herring - and semi-anadromous - perch, carp, etc. - have lost their natural spawning grounds that have developed over the centuries.[ ...]
Salt composition of water. The salt composition of water is understood as the totality of mineral and organic compounds dissolved in it. Depending on the amount of dissolved salts, fresh water is distinguished (up to 0.5% o) (% o - ppm - salt content in g / l of water), brackish (0.5-16.0% o), sea (16-47 %o) and oversalted (more than 47% o). Sea water contains mainly chlorides, while fresh water contains carbonates and sulfates. Therefore, fresh water is hard and soft. Water bodies that are too desalinated, as well as oversalted, are unproductive. Salinity of water is one of the main factors that determine the habitation of fish. Some fish live only in fresh water (freshwater), others - in the sea (marine). Anadromous fish change sea water to fresh water and vice versa. Salinization or desalination of water is usually accompanied by a change in the composition of the ichthyofauna, food supply, and often leads to a change in the entire biocenosis of the reservoir.
Optimal development temperatures can be determined by estimating the intensity of metabolic processes at individual stages (with strict morphological control) by changing oxygen consumption as an indicator of the rate of metabolic reactions at different temperatures. The minimum oxygen consumption for a certain stage of development will correspond to the optimal temperature.
Factors affecting the process of incubation, and the possibility of their regulation.
Of all the abiotic factors, the most powerful in its effect on fish is temperature. Temperature has a very great influence on fish embryogenesis at all stages and stages of embryo development. Moreover, for each stage of embryo development there is an optimal temperature. Optimal temperatures are those temperatures at which the highest rate of metabolism (metabolism) is observed at individual stages without disturbing morphogenesis. The temperature conditions under which embryonic development takes place in natural conditions and with existing methods of incubation of eggs almost never correspond to the maximum manifestation of valuable fish species traits that are useful (necessary) to humans.
Methods for determining the optimal temperature conditions for development in fish embryos are quite complex.
It has been established that in the process of development, the optimum temperature for spring-spawning fish increases, while for autumn-spawning it decreases.
The size of the optimal temperature zone expands as the embryo develops and reaches its largest size before hatching.
Determining the optimal temperature conditions for development allows not only improving the method of incubation (holding prelarvae, rearing larvae, and rearing juveniles), but also opens up the possibility of developing techniques and methods for directing influence on development processes, obtaining embryos with specified morphological and functional properties and specified sizes.
Consider the impact of other abiotic factors on the incubation of eggs.
The development of fish embryos occurs with the constant consumption of oxygen from the external environment and the release of carbon dioxide. A permanent excretion product of embryos is ammonia, which occurs in the body in the process of protein breakdown.
Oxygen. The ranges of oxygen concentrations within which the development of embryos of different fish species is possible differ significantly, and the oxygen concentrations corresponding to the upper limits of these ranges are much higher than those found in nature. Thus, for pike perch, the minimum and maximum oxygen concentrations at which the development of embryos and hatching of prelarvae still occur are 2.0 and 42.2 mg/l, respectively.
It has been established that with an increase in the oxygen content in the range from the lower lethal limit to values significantly exceeding its natural content, the rate of embryo development naturally increases.
Under conditions of deficiency or excess of oxygen concentrations in embryos, there are large differences in the nature of morphofunctional changes. For example, at low oxygen concentrations the most typical anomalies are expressed in body deformation and disproportionate development and even the absence of individual organs, the appearance of hemorrhages in the region of large vessels, the formation of dropsy on the body and gall sac. At elevated oxygen concentrations The most characteristic morphological disturbance in embryos is a sharp weakening or even complete suppression of erythrocyte hematopoiesis. Thus, in pike embryos that developed at an oxygen concentration of 42–45 mg/l, by the end of embryogenesis, erythrocytes in the bloodstream disappear completely.
Along with the absence of erythrocytes, other significant defects are also observed: muscle motility stops, the ability to respond to external stimuli and get rid of the membranes is lost.
In general, embryos incubated at different oxygen concentrations differ significantly in their degree of development at hatching.
Carbon dioxide (CO). Embryonic development is possible in a very wide range of CO concentrations, and the values of concentrations corresponding to the upper limits of these ranges are much higher than those encountered by embryos under natural conditions. But with an excess of carbon dioxide in the water, the number of normally developing embryos decreases. In experiments, it was proved that an increase in the concentration of dioxide in water from 6.5 to 203.0 mg/l causes a decrease in the survival rate of chum salmon embryos from 86% to 2%, and at a carbon dioxide concentration of up to 243 mg/l, all embryos in the process of incubation perished.
It has also been established that the embryos of bream and other cyprinids (roach, blue bream, white bream) develop normally at a carbon dioxide concentration in the range of 5.2-5.7 mg/l, but with an increase in its concentration to 12.1-15.4 mg /l and a decrease in concentration to 2.3-2.8 mg/l, an increased death of these fish was observed.
Thus, both a decrease and an increase in the concentration of carbon dioxide have a negative effect on the development of fish embryos, which gives grounds to consider carbon dioxide as a necessary component of development. The role of carbon dioxide in fish embryogenesis is diverse. An increase in its concentration (within the normal range) in water enhances muscle motility and its presence in the environment is necessary to maintain the level of motor activity of the embryos, with its help, the breakdown of the embryo's oxyhemoglobin occurs and thereby provides the necessary tension in the tissues, it is necessary for the formation of organic compounds of the body.
Ammonia in bony fish, it is the main product of nitrogenous excretion both during embryogenesis and in adulthood. In water, ammonia exists in two forms: in the form of undissociated (not separated) NH molecules and in the form of ammonium ions NH. The ratio between the amount of these forms significantly depends on temperature and pH. With an increase in temperature and pH, the amount of NH increases sharply. The toxic effect on fish is predominantly NH. The action of NH has a negative effect on fish embryos. For example, in trout and salmon embryos, ammonia causes a violation of their development: a cavity filled with a bluish liquid appears around the yolk sac, hemorrhages form in the head section, and motor activity decreases.
Ammonium ions at a concentration of 3.0 mg/l cause a slowdown in linear growth and an increase in the body weight of pink salmon embryos. At the same time, it should be borne in mind that ammonia in bony fish can be re-involved in metabolic reactions and the formation of non-toxic products.
Hydrogen indicator pH of water, in which embryos develop, should be close to the neutral level - 6.5-7.5.
water requirements. Before water is supplied to the incubation apparatus, it must be cleaned and neutralized using sedimentation tanks, coarse and fine filters, and bactericidal installations. The development of embryos can be negatively affected by the brass mesh used in the incubation apparatus, as well as fresh wood. This effect is especially pronounced if sufficient flow is not ensured. Exposure to a brass mesh (more precisely, copper and zinc ions) causes inhibition of growth and development, and reduces the vitality of embryos. Exposure to substances extracted from wood leads to dropsy and anomalies in the development of various organs.
Water flow. For the normal development of embryos, water flow is necessary. The lack of flow or its insufficiency has the same effect on embryos as a lack of oxygen and an excess of carbon dioxide. If there is no water change at the surface of the embryos, then the diffusion of oxygen and carbon dioxide through the shell does not provide the necessary intensity of gas exchange, and the embryos experience a lack of oxygen. Despite the normal saturation of the water in the incubation apparatus. The efficiency of water exchange depends more on the circulation of water around each egg than on the total amount of incoming water and its speed in the incubation apparatus. Efficient water exchange during the incubation of eggs in a stationary state (salmon caviar) is created when water circulates perpendicular to the plane of the frames with eggs - from bottom to top with an intensity of 0.6-1.6 cm/sec. This condition is fully met by the IM incubation apparatus, which imitates the conditions of water exchange in natural spawning nests.
For the incubation of beluga and stellate sturgeon embryos, the optimal water consumption is 100-500 and 50-250 ml per embryo per day, respectively. Before hatching, the prelarvae in the incubation apparatus increase the water flow in order to ensure normal conditions for gas exchange and the removal of metabolic products.
It is known that low salinity (3-7) is detrimental to pathogenic bacteria, fungi and has a beneficial effect on the development and growth of fish. In water with a salinity of 6-7, not only the waste of developing normal embryos decreases and the growth of juveniles accelerates, but also overripe eggs develop, which die in fresh water. An increased resistance of embryos developing in brackish water to mechanical stress was also noted. Therefore, the question of the possibility of rearing anadromous fish in brackish water from the very beginning of their development has acquired great importance recently.
The influence of light. When carrying out incubation, it is necessary to take into account the adaptability of embryos and prelarvae of various fish species to lighting. For example, for salmon embryos, light is detrimental, so the incubation apparatus must be darkened. Incubation of sturgeon eggs in complete darkness, on the contrary, leads to a delay in development. Exposure to direct sunlight causes inhibition of the growth and development of sturgeon embryos and a decrease in the viability of prelarvae. This is due to the fact that sturgeon caviar under natural conditions develops in muddy water and at a considerable depth, that is, in low light. Therefore, during the artificial reproduction of sturgeons, the incubation apparatus should be protected from direct sunlight, as it can cause damage to the embryos and the appearance of freaks.
Care of eggs during incubation.
Before the start of the fish breeding cycle, all hatching apparatus must be repaired and disinfected with a bleach solution, rinsed with water, walls and floors washed with a 10% lime solution (milk). For prophylactic purposes against damage to eggs by saprolegnia, it must be treated with a 0.5% formalin solution for 30-60 seconds before being loaded into the incubation apparatus.
Caviar care during the incubation period consists in monitoring the temperature, oxygen concentration, carbon dioxide, pH, flow, water level, light regime, the state of the embryos; selection of dead embryos (with special tweezers, screens, pears, siphon); preventive treatment as needed. Dead eggs are whitish in color. When salmon caviar is silted, showering is carried out. Persuasion and selection of dead embryos should be carried out during periods of reduced sensitivity.
The duration and features of the incubation of eggs of various fish species. Hatching of prelarvae in various incubators.
The duration of incubation of eggs is largely dependent on the temperature of the water. Usually, with a gradual increase in water temperature within the optimal limits for the embryogenesis of a particular species, the development of the embryo gradually accelerates, but when approaching the temperature maximum, the development rate increases less and less. At temperatures close to the upper threshold, in the early stages of crushing of fertilized eggs, its embryogenesis, despite the increase in temperature, slows down, and with a greater increase, death of the eggs occurs.
Under unfavorable conditions (insufficient flow, overload of incubators, etc.), the development of incubated eggs slows down, hatching starts late and takes longer. The difference in the duration of development at the same water temperature and different flow rates and loads can reach 1/3 of the incubation period.
Features of incubation of eggs of various fish species. (sturgeon and salmon).
Sturgeon.: supply of incubation apparatus with water with oxygen saturation of 100%, carbon dioxide concentration of not more than 10 mg / l, pH - 6.5-7.5; protection from direct sunlight to avoid damage to the embryos and the appearance of malformations.
For stellate sturgeon, the optimal temperature is from 14 to 25 C, at a temperature of 29 C, the development of embryos is inhibited, at 12 C - a large death and many freaks appear.
For the sturgeon of the spring run, the optimal incubation temperature is 10-15 C (incubation at a temperature of 6-8 C leads to 100% death, and at 17-19 C many abnormal prelarvae appear.)
Salmon. The optimal level of oxygen at the optimum temperature for salmonids is 100% of saturation, the level of dioxide is not more than 10 mg/l (for pink salmon, no more than 15 is acceptable, and no more than 20 mg/l), pH is 6.5-7.5; complete blackout during incubation of salmon caviar, protection of whitefish caviar from direct sunlight.
For Baltic salmon, salmon, Ladoga salmon, the optimum temperature is 3-4 C. After hatching, the optimum temperature rises to 5-6, and then to 7-8 C.
Incubation of whitefish caviar mainly occurs at a temperature of 0.1-3 C for 145-205 days, depending on the type and thermal regime.
Hatching. The duration of hatching is not constant and depends not only on temperature, gas exchange, and other incubation conditions, but also on the specific conditions (flow rate in the incubation apparatus, shocks, etc.) necessary for the release of the embryo hatching enzyme from the shells. The worse the conditions, the longer the duration of hatching.
Usually, under normal environmental conditions, the hatching of viable prelarvae from one batch of eggs is completed in sturgeon within a few hours to 1.5 days, in salmon - 3-5 days. The moment when there are already several dozen prelarvae in the incubation apparatus can be considered the beginning of the hatching period. Usually, after this, mass hatching occurs, and at the end of hatching, dead and ugly embryos remain in the shells in the apparatus.
Extended hatching periods most often indicate unfavorable environmental conditions and lead to an increase in the heterogeneity of prelarvae and an increase in their mortality. Hatching is a big inconvenience for the fish farmer, so it is important to know the following.
The hatching of the embryo from the eggs depends largely on the release of the hatching enzyme in the hatching gland. This enzyme appears in the gland after the onset of heart pulsation, then its amount rapidly increases until the last stage of embryogenesis. At this stage, the enzyme is released from the gland into the perivitelin fluid, the enzymatic activity of which sharply increases, and the activity of the gland decreases. The strength of the membranes with the appearance of the enzyme in the perivitelin fluid rapidly decreases. Moving in weakened membranes, the embryo breaks them, enters the water and becomes a prelarva. The release of the hatching enzyme and muscle activity, which is of paramount importance for release from the membranes, is more dependent on external conditions. They are stimulated by the improvement of aeration conditions, the movement of water, and shocks. To ensure unanimous hatching, for example, in sturgeons, the following are necessary: strong flow and vigorous mixing of eggs in the incubation apparatus.
The timing of hatching of prelarvae also depends on the design of the incubation apparatus. Thus, in sturgeons, the most favorable conditions for friendly hatching are created in the sturgeon incubator, in Yushchenko's devices, the hatching of larvae is significantly extended, and even less favorable conditions for hatching are in the Sadov and Kakhanskaya trough incubators.
TOPIC. BIOLOGICAL FOUNDATIONS FOR PRE-LARGER HOLDING, MATERIAL GROWTH AND GROWING OF YOUNG FISH.
The choice of fish-breeding equipment depending on the ecological and physiological properties of the species.
In the modern technological process of factory reproduction of fish, after the incubation of eggs, the holding of prelarvae, rearing of larvae and rearing of juveniles begins. Such a technological scheme provides for complete fish-breeding control during the formation of the fish organism, when important biological transformations of the developing organism take place. For sturgeon and salmon, for example, such transformations include the formation of an organ system, growth and development, and physiological preparation for life in the sea.
In all cases, violations of environmental conditions and breeding technology associated with the lack of correct ideas about certain features of the biology of the farmed object or the mechanical use of fish breeding techniques of equipment and regime, without understanding the biological meaning, entail an increased death of farmed fish in the period of early ontogenesis.
One of the most critical periods of the entire biotechnical process of artificial reproduction of fish is the holding of prelarvae and rearing of larvae.
The prelarvae released from their shells go through the stage of a passive state in their development, which is characterized by low mobility. When keeping prelarvae, the adaptive features of this period of development of the given species are taken into account, and conditions are created that ensure the greatest survival before switching to active feeding. With the transition to active (exogenous) nutrition, the next link in the fish breeding process begins - rearing larvae.
Of the 40-41 thousand species of vertebrates that exist on earth, fish is the most species-rich group: it has over 20 thousand living representatives. Such a variety of species is explained, first of all, by the fact that fish are one of the most ancient animals on earth - they appeared 400 million years ago, that is, when there were no birds, amphibians, or mammals on the globe . During this period, fish have adapted to live in a wide variety of conditions: they live in the World Ocean, at depths of up to 10,000 m, and in alpine lakes, at an altitude of up to 6,000 m, some of them can live in mountain rivers, where the water speed reaches 2 m / s, and others - in stagnant water bodies.
Of the 20 thousand species of fish, 11.6 thousand are marine, 8.3 thousand are freshwater, and the rest are anadromous. All fish belonging to a number of fish, on the basis of their similarity and relationship, are divided according to the scheme developed by the Soviet academician L. S. Berg into two classes: cartilaginous and bone. Each class consists of subclasses, subclasses of superorders, superorders of orders, orders of families, families of genera, and genera of species.
Each species has characteristics that reflect its adaptability to certain conditions. All individuals of a species can interbreed and produce offspring. Each species in the process of development has adapted to the known conditions of reproduction and nutrition, temperature and gas conditions, and other factors of the aquatic environment.
The shape of the body is very diverse, which is caused by the adaptation of fish to various, sometimes very peculiar, conditions of the aquatic environment (Fig. 1.). The following forms are most common: torpedo-shaped, arrow-shaped, ribbon-shaped, eel-shaped, flat and spherical.
The body of the fish is covered with skin, which has the upper layer - the epidermis and the lower - the corium. The epidermis consists of a large number of epithelial cells; in this layer there are mucus secretion, pigment, luminous and poisonous glands. The corium, or skin proper, is a connective tissue permeated with blood vessels and nerves. There are also clusters of large pigment cells and guanine crystals, which give the skin of fish a silvery color.
In most fish, the body is covered with scales. It does not exist in fish swimming at low speeds. The scales ensure the smoothness of the surface of the body and prevent the appearance of skin folds on the sides.
Freshwater fish have bony scales. According to the nature of the surface, two types of bony scales are distinguished: cycloid with a smooth posterior edge (cyprinids, herring) and ctenoid, the posterior edge of which is armed with spines (perch). The age of bony fish is determined from annual rings of bony scales (Fig. 2).
The age of the fish is also determined by the bones (bones of the gill cover, jawbone, large integumentary bone of the shoulder girdle - cleistrum, sections of hard and soft rays of the fins, etc.) and otoliths (calcareous formations in the ear capsule), where, as on the scales, stratifications corresponding to the annual cycles of life.
The body of sturgeon fish is covered with a special type of scales - bugs, they are located on the body in longitudinal rows, have a conical shape.
The skeleton of fish can be cartilaginous (sturgeon and lampreys) and bone (all other fish).
Fish fins are: paired - pectoral, ventral and unpaired - dorsal, anal, caudal. The dorsal fin can be one (for cyprinids), two (for perch) and three (for cod). The adipose fin without bony rays is a soft skin outgrowth on the back of the back (in salmon). The fins provide balance to the body of the fish and its movement in different directions. The caudal fin creates a driving force and acts as a rudder, providing maneuverability of the fish when turning. The dorsal and anal fins support the normal position of the body of the fish, that is, they act as a keel. Paired fins maintain balance and are rudders of turns and depth (Fig. 3).
The respiratory organ is the gills, which are located on both sides of the head and are covered with covers. When breathing, the fish swallows water through the mouth and pushes it out through the gills. Blood from the heart enters the gills, enriched with oxygen, and spreads through the circulatory system. Carp, crucian carp, catfish, eel, loach and other fish that inhabit lake water bodies, where oxygen is often lacking, are able to breathe with their skin. In some fish, the swim bladder, intestines, and special additional organs are able to use atmospheric oxygen. So, snakehead, basking in shallow water, can breathe air through the supragillary organ. The circulatory system of fish consists of the heart and blood vessels. Their heart is two-chambered (has only an atrium and a ventricle), directs venous blood through the abdominal aorta to the gills. The most powerful blood vessels run along the spine. Fish have only one circulation. The digestive organs of fish are the mouth, pharynx, esophagus, stomach, liver, intestines, ending in the anus.
The shape of the mouth in fish is varied. Plankton-feeding fish have an upper mouth, bottom-feeding fish have a lower mouth, and predatory fish have a terminal mouth. Many fish have teeth. Carp fish have pharyngeal teeth. Behind the mouth of the fish is the oral cavity, where food initially enters, then it goes to the pharynx, esophagus, stomach, where it begins to be digested under the action of gastric juice. Partially digested food enters the small intestine, where the ducts of the pancreas and liver flow. The latter secretes bile, which accumulates in the gallbladder. Carp fish do not have a stomach, and food is digested in the intestines. Undigested food remains are excreted into the hindgut and through the anus are removed to the outside.
The excretory system of fish serves to remove metabolic products and ensure the water-salt composition of the body. The main organs of excretion in fish are the paired trunk kidneys with their excretory ducts - the ureters, through which urine enters the bladder. To some extent, the skin, gills and intestines take part in excretion (removal of end products of metabolism from the body).
The nervous system is divided into the central nervous system, which includes the brain and spinal cord, and the peripheral nervous system, which is the nerves extending from the brain and spinal cord. Nerve fibers depart from the brain, the endings of which come to the surface of the skin and form in most fish a pronounced lateral line that runs from the head to the beginning of the rays of the caudal fin. The lateral line serves to orient the fish: determine the strength and direction of the current, the presence of underwater objects, etc.
The organs of vision - two eyes - are located on the sides of the head. The lens is round, does not change shape and almost touches the flat cornea, therefore the fish are short-sighted: most of them distinguish objects at a distance of up to 1 m, and at most 1 they see no more than 10-15 m.
The nostrils are located in front of each eye, leading to a blind olfactory sac.
The organ of hearing of fish is also an organ of balance, it is located in the back of the skull, a cartilaginous, or bone, chamber: it consists of upper and lower sacs in which otoliths are located - pebbles consisting of calcium compounds.
Taste organs in the form of microscopic taste cells are located in the membrane of the oral cavity and on the entire surface of the body. Fish have a well-developed sense of touch.
The reproductive organs in females are the ovaries (ovaries), in males - the testes (milk). Inside the ovary there are eggs, which in different fish have different sizes and colors. The caviar of most fish is edible and is a highly valuable food product. Sturgeon and salmon caviar is distinguished by the highest nutritional quality.
The hydrostatic organ that provides buoyancy to fish is a swim bladder filled with a mixture of gases and located above the entrails. Some demersal fish lack a swim bladder.
The temperature sense of fish is associated with receptors located in the skin. The simplest reaction of fish to a change in water temperature is to move to places where the temperature is more favorable for them. Fish do not have mechanisms of thermoregulation, their body temperature is unstable and corresponds to the temperature of the water or differs slightly from it.
Fish and the environment
Not only different types of fish live in the water, only different types of fish, but also thousands of living beings, plants and microscopic organisms. Reservoirs where fish live differ from each other in physical and chemical properties. All these factors affect the biological processes occurring in the water and, consequently, the life of fish.
The relationship of fish with the environment is combined into two groups of factors: abiotic and biotic.
Biotic factors include the world of animal and plant organisms that surround the fish in the water and act on it. This also includes intraspecific and interspecific relationships of fish.
The physical and chemical properties of water (temperature, salinity, gas content, etc.) that affect fish are called abiotic factors. Abiotic factors also include the size of the reservoir and its depth.
Without knowledge and study of these factors, it is impossible to successfully engage in fish farming.
The anthropogenic factor is the impact of human economic activity on the reservoir. Land reclamation increases the productivity of water bodies, while pollution and water abstraction reduce their productivity or turn them into dead water bodies.
Abiotic factors of water bodies
The aquatic environment where the fish lives has certain physical and chemical properties, the change of which is reflected in the biological processes occurring in the water, and, consequently, in the life of fish and other living organisms and plants.
Water temperature. Different types of fish live at different temperatures. So, in the mountains of California, the lukaniye fish lives in warm springs at a water temperature of + 50 ° C and above, and crucian carp spend the winter in hibernation at the bottom of a frozen reservoir.
Water temperature is an important factor for the life of fish. It affects the timing of spawning, development of eggs, growth rate, gas exchange, digestion.
Oxygen consumption is directly dependent on water temperature: when it decreases, oxygen consumption decreases, and when it increases, it increases. The temperature of the water also affects the nutrition of fish. With its increase, the rate of digestion of food in fish increases, and vice versa. So, carp feeds most intensively at water temperature +23...+29°C, and at +15...+17°C it reduces its nutrition by three to four times. Therefore, pond farms constantly monitor the water temperature. In fish farming, pools at thermal and nuclear power plants, underground thermal waters, warm sea currents, etc. are widely used.
The fish of our reservoirs and seas are divided into heat-loving (carp, sturgeon, catfish, eels) and cold-loving (cod and salmon). In the reservoirs of Kazakhstan, mainly heat-loving fish live, with the exception of bred new fish, such as trout and whitefish, which are cold-loving. Some species - crucian carp, pike, roach, marinka and others - withstand fluctuations in water temperature from 20 to 25 ° C.
Heat-loving fish (carp, bream, roach, catfish, etc.) in winter concentrate in areas of the deep zone determined for each species, they show passivity, their feeding slows down or stops completely.
Fish that lead an active lifestyle in the winter (salmon, whitefish, pike perch, etc.) are cold-loving.
The distribution of commercial fish in large bodies of water usually depends on the temperature in different parts of this body of water. It is used for fishing and commercial reconnaissance.
Salinity of water also acts on fish, although most of them withstand its vibrations. The salinity of water is defined in thousandths: 1 ppm is equal to 1 g of dissolved salts in 1 liter of sea water, and it is indicated by the sign ‰. Some fish species can withstand water salinity up to 70‰, i.e. 70 g/l.
According to the habitat and in relation to the salinity of the water, fish are usually divided into four groups: marine, freshwater, anadromous and brackish-water.
Marine include fish that live in the oceans and coastal sea waters. Freshwater fish constantly live in fresh water. Anadromous fish for breeding either move from sea water to fresh water (salmon, herring, sturgeon) or from fresh water to sea water (some eels). Brackish-water fish live in desalinated areas of the seas and in inland seas with low salinity.
For fish living in lake reservoirs, ponds and rivers, it is important the presence of gases dissolved in water- oxygen, hydrogen sulfide and other chemical elements, as well as the smell, color and taste of water.
An important indicator for the life of fish is amount of dissolved oxygen in water. For carp fish, it should be 5-8, for salmon - 8-11 mg / l. When the oxygen concentration decreases to 3 mg/l, the carp feels bad and eats worse, and at 1.2-0.6 mg/l it can die. When the lake becomes shallow, when the water temperature rises and when it is overgrown with vegetation, the oxygen regime deteriorates. In shallow reservoirs, when their surface is covered with a dense layer of ice and snow in winter, the access of atmospheric oxygen stops and after a while, usually in March (if you do not make an ice hole), the death of fish begins from oxygen starvation, or the so-called "zamora".
Carbon dioxide plays an important role in the life of a reservoir, is formed as a result of biochemical processes (decomposition of organic matter, etc.), it combines with water and forms carbonic acid, which, interacting with bases, gives bicarbonates and carbonates. The content of carbon dioxide in water depends on the time of year and the depth of the reservoir. In summer, when aquatic plants absorb carbon dioxide, there is very little of it in the water. High concentrations of carbon dioxide are harmful to fish. When the content of free carbon dioxide is 30 mg/l, the fish feeds less intensively, its growth slows down.
hydrogen sulfide It is formed in water in the absence of oxygen and causes the death of fish, and the strength of its action depends on the temperature of the water. At high water temperatures, fish quickly die from hydrogen sulfide.
With the overgrowth of reservoirs and the decay of aquatic vegetation, the concentration of dissolved organic substances in the water increases and the color of the water changes. In swampy water bodies (brown water), fish cannot live at all.
Transparency- one of the important indicators of the physical properties of water. In clean lakes, plant photosynthesis proceeds at a depth of 10-20 m, in reservoirs with low-transparency water - at a depth of 4-5 m, and in ponds in summer the transparency does not exceed 40-60 cm.
The degree of water transparency depends on a number of factors: in rivers - mainly on the amount of suspended particles and, to a lesser extent, on dissolved and colloidal substances; in stagnant water bodies - ponds and lakes - mainly from the course of biochemical processes, for example, from the blooming of water. In any case, the decrease in the transparency of water is associated with the presence of the smallest suspended mineral and organic particles in it. Getting on the gills of fish, they make it difficult for them to breathe.
Pure water is a chemically neutral compound with equally acidic and alkaline properties. Hydrogen and hydroxyl ions are present in equal amounts. Based on this property of pure water, the concentration of hydrogen ions is determined in pond farms; for this purpose, a water pH indicator has been established. When the pH is 7, then this corresponds to the neutral state of water, less than 7 is acidic, and above 7 is alkaline.
In most fresh water bodies, the pH is 6.5-8.5. In summer, with intensive photosynthesis, an increase in pH to 9 and above is observed. In winter, when carbon dioxide accumulates under the ice, its lower values are observed; The pH also changes during the day.
In pond and lake-commodity fish farming, regular monitoring of water quality is established: the pH of the water, color, transparency and its temperature are determined. Each fish farm for conducting hydrochemical water analysis has its own laboratory equipped with the necessary instruments and reagents.
Biotic factors of water bodies
Biotic factors are of great importance for the life of fish. In each reservoir, sometimes dozens of species of fish mutually exist, which differ from each other in the nature of their diet, location in the reservoir, and other characteristics. Distinguish intraspecific, interspecific relationships of fish, as well as the relationship of fish with other aquatic animals and plants.
Intraspecific relations of fish are aimed at ensuring the existence of a species by forming single-species groups: schools, elementary populations, aggregations, etc.
Many fish lead flock image life (Atlantic herring, anchovy, etc.), and most fish gather in flocks only at a certain period (during spawning or feeding). Flocks are formed from fish of a similar biological state and age and are united by the unity of behavior. Schooling is an adaptation of fish to find food, find migration routes, and protect themselves from predators. A school of fish is often called a school. However, there are some species that do not gather in flocks (catfish, many sharks, lumpfish, etc.).
An elementary population represents a grouping of fish, mostly of the same age, similar in physiological state (fatness, degree of puberty, amount of hemoglobin in the blood, etc.), and persists for life. They are called elementary because they do not break up into any intraspecific biological groups.
A herd, or population, is a single-species self-reproducing group of fish of different ages, inhabiting a certain area and tied to certain places of reproduction, feeding and wintering.
An accumulation is a temporary association of several schools and elementary fish populations, which is formed as a result of a number of reasons. These include collections:
spawning, arising for reproduction, consisting almost exclusively of sexually mature individuals;
migratory, arising on the ways of movement of fish for spawning, feeding or wintering;
feeding, formed at the places of feeding of fish and caused mainly by the concentration of food objects;
wintering, arising in the wintering places of fish.
Colonies form as temporary protective groups of fish, usually consisting of individuals of the same sex. They are formed at breeding sites to protect egg clutches from enemies.
The nature of the reservoir and the number of fish in it affect their growth and development. So, in small reservoirs, where there are a lot of fish, they are smaller than in large reservoirs. This can be seen in the example of carp, bream and other fish species, which have become larger in the Bukhtarma, Kapchagai, Chardara and other reservoirs than they were before in the former lake. Zaisan, the Balkhash-Ili basin and in the lake reservoirs of the Kzyl-Orda region.
An increase in the number of fish of one species often leads to a decrease in the number of fish of another species. So, in reservoirs where there is a lot of bream, the number of carp is reduced, and vice versa.
There is competition between individual fish species for food. If there are predatory fish in the reservoir, peaceful and smaller fish serve as food for them. With an excessive increase in the number of predatory fish, the number of fish that serve as food for them decreases and, at the same time, the breed quality of predatory fish deteriorates, they are forced to switch to cannibalism, that is, they eat individuals of their own species and even their descendants.
The nutrition of fish is different, depending on their type, age, and also the time of year.
stern fish are planktonic and benthic organisms.
Plankton from the Greek planktos - soaring - is a collection of plant and animal organisms that live in water. They are completely devoid of organs of movement, or have weak organs of movement that cannot resist the movement of water. Plankton is divided into three groups: zooplankton - animal organisms represented by various invertebrates; phytoplankton are plant organisms represented by a variety of algae, and bacterioplankton occupies a special place (Fig. 4 and 5).
Planktonic organisms tend to be small and have a low density, which helps them float in the water column. Freshwater plankton consists mainly of protozoa, rotifers, cladocerans and copepods, green, blue-green and diatoms. Many of the planktonic organisms are food for juvenile fish, and some are also eaten by adult planktivorous fish. Zooplankton has high nutritional qualities. So, in daphnia, the dry matter of the body contains 58% protein and 6.5% fat, and in cyclops - 66.8% protein and 19.8% fat.
The population of the bottom of the reservoir is called benthos, from the Greek benthos- depth (Fig. 6 and 7). Benthic organisms are represented by diverse and numerous plants (phytobenthos) and animals (zoobenthos).
By nature of food fish of inland waters are divided into:
1. Herbivores that eat mainly aquatic flora (grass carp, silver carp, roach, rudd, etc.).
2. Animal eaters that eat invertebrates (roach, bream, whitefish, etc.). They are divided into two subgroups:
planktophages that feed on protozoa, diatoms and some algae (phytoplankton), some coelenterates, molluscs, eggs and larvae of invertebrates, etc.;
benthophages that feed on organisms that live on the ground and in the soil of the bottom of reservoirs.
3. Ichthyophages, or carnivores that feed on fish, vertebrates (frogs, waterfowl, etc.).
However, this division is conditional.
Many fish have a mixed diet. For example, carp is omnivorous, eating both plant and animal food.
The fish are different according to the nature of the laying of eggs during the spawning period. The following ecological groups are distinguished here;
lithophiles- breed on rocky ground, usually in rivers, on the current (sturgeon, salmon, etc.);
phytophiles- breed among plants, lay eggs on vegetative or dead plants (carp, carp, bream, pike, etc.);
psammophiles- lay eggs on the sand, sometimes attaching it to the roots of plants (peled, vendace, gudgeon, etc.);
pelagophiles- they spawn into the water column, where it develops (amour, silver carp, herring, etc.);
ostracophiles- lay eggs inside
the mantle cavity of molluscs and sometimes under the shells of crabs and other animals (mustards).
Fish are in a complex relationship with each other, life and their growth depend on the state of water bodies, on biological and biochemical processes occurring in the water. For artificial breeding of fish in reservoirs and for the organization of commercial fish farming, it is necessary to study well the existing reservoirs and ponds, to know the biology of fish. Fish-breeding activities carried out without knowledge of the matter can only cause harm. Therefore, fishery enterprises, state farms, collective farms should have experienced fish farmers and ichthyologists.
CHAPTER I
STRUCTURE AND SOME PHYSIOLOGICAL FEATURES OF FISH
EXECUTIVE SYSTEM AND OSMOREGULATION
Unlike higher vertebrates, which have a compact pelvic kidney (metanephros), fish have a more primitive trunk kidney (mesonephros), and their embryos have a pronephros (pronephros). In some species (goby, atherina, eelpout, mullet), the pronephros in one form or another performs an excretory function in adults as well; in most adult fish, the mesonephros becomes the functioning kidney.
The kidneys are paired, dark red formations elongated along the body cavity, tightly adjacent to the spine, above the swim bladder (Fig. 22). In the kidney, an anterior section (head kidney), middle and posterior are distinguished.
Arterial blood enters the kidneys through the renal arteries, venous blood through the portal veins of the kidneys.
Rice. 22. Trout kidney (according to Stroganov, 1962):
1 - superior vena cava, 2 - efferent renal veins, 3 - ureter, 4 - bladder
The morphophysiological element of the kidney is the convoluted renal tubule, one end of which expands into the Malpighian body, and the other goes to the ureter. The glandular cells of the walls secrete nitrogenous decay products (urea), which enter the lumen of the tubules. Here, in the walls of the tubules, there is a reverse absorption of water, sugars, vitamins from the filtrate of the Malpighian bodies.
Malpighian body - a glomerulus of arterial capillaries, covered by the expanded walls of the tubule, - forms the Bowman's capsule. In primitive forms (sharks, rays, sturgeons), a ciliated funnel departs from the tubule in front of the capsule. Malpighian glomerulus serves as an apparatus for filtering liquid metabolic products. Both metabolic products and substances important for the body enter the filtrate. The walls of the renal tubules are permeated with capillaries of the portal veins and vessels from Bowman's capsules.
Purified blood returns to the vascular system of the kidneys (renal vein), and metabolic products filtered from the blood and urea are excreted through the tubule into the ureter. The ureters drain into the bladder (urinary sinus) and then the urine is expelled to the outside 91; in males of most bony fish through the urogenital opening behind the anus, and in females of teleosts and males of salmon, herring, and some other pike - through the anus. In sharks and rays, the ureter opens into the cloaca.
In addition to the kidneys, skin, gill epithelium, and the digestive system take part in the processes of excretion and water-salt metabolism (see below).
The living environment of fish - sea and fresh water - always has a greater or lesser amount of salts, therefore osmoregulation is the most important condition for the life of fish.
The osmotic pressure of aquatic animals is created by the pressure of their abdominal fluids, the pressure of the blood and body juices. The decisive role in this process belongs to the water-salt exchange.
Each cell of the body has a shell: it is semi-permeable, that is, it is differently permeable to water and salts (it passes water and is salt-selective). Water-salt metabolism of cells is determined primarily by the osmotic pressure of blood and cells.
According to the level of osmotic pressure of the internal environment in relation to the surrounding water, the fish form several groups: in myxines, the cavity fluids are isotonic with the environment; in sharks and rays, the concentration of salts in body fluids and osmotic pressure are slightly higher than in sea water, or almost equal to it (achieved due to the difference in the salt composition of blood and sea water and due to urea); in bony fish - both marine and freshwater (as well as in more highly organized vertebrates) - the osmotic pressure inside the body is not equal to the osmotic pressure of the surrounding water. In freshwater fish it is higher, in marine fish (as in other vertebrates) it is lower than in the environment (Table 2).
table 2
The value of blood depression for large groups of fish (according to Stroganov, 1962)
A group of fish. Depression D°Blood. Depression D ° External environment. Average osmotic pressure, Pa. Blood Mean osmotic pressure, Pa
External environment.
Bony: marine. 0.73. 1.90-2.30. 8.9 105. 25.1 105.
Bony: freshwater. 0.52. 0.02-0.03. 6.4 105. 0.3 105.
If a certain level of osmotic pressure of body fluids is maintained in the body, then the conditions for the vital activity of cells become more stable and the body is less dependent on fluctuations in the external environment.
Real fish have this property - to maintain the relative constancy of the osmotic pressure of blood and lymph, i.e., the internal environment; therefore, they belong to homoiosmotic organisms (from the Greek. ‛gomoyos‛ - homogeneous).
But in different groups of fish, this independence of osmotic pressure is expressed and achieved in different ways,
In marine bony fish, the total amount of salts in the blood is much lower than in sea water, the pressure of the internal environment is less than the pressure of the external one, that is, their blood is hypotonic with respect to sea water. Below are the values of fish blood depression (according to Stroganov, 1962):
Type of fish. Depression of the environment D°.
Marine:
Baltic cod - 0,77
sea flounder - 0,70
mackerel - 0,73
rainbow trout - 0,52
burbot - 0,48
Freshwater:
carp - 0,42
tench - 0,49
Pike - 0,52
Checkpoints:
eel in the sea 0,82
in a river - 0,63
stellate sturgeon in the sea - 0,64
in a river - 0,44
In freshwater fish, the amount of salts in the blood is higher than in fresh water. The pressure of the internal environment is greater than the pressure of the external, their blood is hypertonic.
Maintaining the salt composition of the blood and its pressure at the desired level is determined by the activity of the kidneys, special cells of the walls of the renal tubules (urea excretion), gill filaments (ammonia diffusion, chloride excretion), skin, intestines, and liver.
In marine and freshwater fish, osmoregulation takes place in different ways (specific activity of the kidneys, different permeability of the integument for urea, salts and water, different activity of the gills in sea and fresh water).
In freshwater fish (with hypertonic blood) in a hypotonic environment, the difference in osmotic pressure inside and outside the body leads to the fact that water from the outside continuously enters the body - through the gills, skin and oral cavity (Fig. 23).
Rice. 23. Mechanisms of osmoregulation in bony fish
A - freshwater; B - marine (according to Stroganov, 1962)
In order to avoid excessive watering, to maintain the water-salt composition and the level of osmotic pressure, it becomes necessary to remove excess water from the body and simultaneously retain salts. In this regard, freshwater fish develop powerful kidneys. The number of Malpighian glomeruli and renal tubules is large; they excrete much more urine than close marine species. Data on the amount of urine excreted by fish per day are presented below (according to Stroganov, 1962):
Type of fish. Amount of urine, ml/kg of body weight
Freshwater:
carp - 50–120
trout - 60– 106
catfish dwarf - 154 – 326
Marine:
goby - 3–23
angler - 18
Checkpoints:
eel in fresh water 60–150
at sea - 2–4
The loss of salts with urine, feces and through the skin is replenished in freshwater fish by obtaining them with food due to the specialized activity of the gills (the gills absorb Na and Cl ions from fresh water) and the absorption of salts in the renal tubules.
Marine bony fish (with hypotonic blood) in a hypertonic environment constantly lose water - through the skin, gills, with urine, excrement. Preventing dehydration of the body and maintaining the osmotic pressure at the desired level (i.e., lower than in sea water) is achieved by drinking sea water, which is absorbed through the walls of the stomach and intestines, and excess salts are excreted by the intestines and gills.
Eel and sculpin in sea water drink 50–200 cm3 of water per 1 kg of body weight daily. Under the conditions of the experiment, when the water supply through the mouth (closed with a cork) was stopped, the fish lost 12%–14% of its mass and died on the 3rd–4th day.
Marine fish excrete very little urine: they have few malpighian glomeruli in their kidneys, some do not have them at all and have only renal tubules. They have reduced skin permeability to salts, the gills secrete Na and Cl ions outward. The glandular cells of the walls of the tubules increase the excretion of urea and other products of nitrogen metabolism.
Thus, in non-migratory fish - only marine or only freshwater - there is one, specific for them, method of osmoregulation.
Euryhaline organisms (that is, those that can withstand significant fluctuations in salinity), in particular migratory fish, spend part of their life in the sea, and part in fresh water. When moving from one environment to another, for example during spawning migrations, they endure large fluctuations in salinity.
This is possible due to the fact that migratory fish can switch from one method of osmoregulation to another. In sea water, they have the same osmoregulation system as in marine fish, in fresh water - like in fresh water, so that their blood in sea water is hypotonic, and in fresh water it is hypertonic.
Their kidneys, skin, and gills can function in two ways: the kidneys have renal glomeruli with renal tubules, as in freshwater fish, and only renal tubules, as in marine fish. The gills are equipped with specialized cells (the so-called Case-Wilmer cells) capable of absorbing and releasing Cl and Na (whereas in marine or freshwater fish they act only in one direction). The number of such cells also changes. When moving from fresh water to the sea, the number of chloride-secreting cells in the gills of the Japanese eel increases. In the river lamprey, when rising from the sea to the rivers, the amount of urine excreted during the day increases up to 45% compared to body weight.
In some anadromous fish, mucus secreted by the skin plays an important role in the regulation of osmotic pressure.
The anterior part of the kidney - the head kidney - performs not an excretory, but a hematopoietic function: the portal vein of the kidneys does not enter it, and red and white blood cells are formed in its constituent lymphoid tissue and obsolete erythrocytes are destroyed.
Like the spleen, the kidneys sensitively reflect the state of the fish, decreasing in volume with a lack of oxygen in the water and increasing when the metabolism slows down (for carp - during wintering, when the activity of the circulatory system is weakened), in case of acute diseases, etc.
The additional function of the kidneys in the stickleback, which builds a nest from pieces of plants for spawning, is very peculiar: before spawning, the kidneys increase, a large amount of mucus is produced in the walls of the renal tubules, which quickly hardens in the water and holds the nest together.
Rice. Fish scale shape. a - placoid; b - ganoid; c - cycloid; d - ctenoid
Placoid - the most ancient, preserved in cartilaginous fish (sharks, rays). It consists of a plate on which a spine rises. Old scales are discarded, new ones appear in their place. Ganoid - mainly in fossil fish. The scales are rhombic in shape, closely articulated with each other, so that the body is enclosed in a shell. Scales do not change over time. The scales owe their name to ganoin (dentine-like substance), which lies in a thick layer on the bone plate. Among modern fish, armored pikes and multifins have it. In addition, sturgeons have it in the form of plates on the upper lobe of the caudal fin (fulcra) and scutes scattered over the body (a modification of several merged ganoid scales).
Gradually changing, the scales lost ganoin. Modern bony fish no longer have it, and the scales consist of bony plates (bone scales). These scales can be cycloid - rounded, with smooth edges (cyprinids) and ctenoid with a serrated trailing edge (percids). Both forms are related, but the cycloid, as a more primitive one, is found in low-organized fish. There are cases when, within the same species, males have ctenoid scales, and females have cycloid scales (flounders of the genus Liopsetta), or even scales of both forms are found in one individual.
The size and thickness of the scales in fish vary greatly - from microscopic scales of an ordinary eel to very large, palm-sized scales of a three-meter long barbel that lives in Indian rivers. Only a few fish do not have scales. In some, it merged into a solid, immovable shell, like a boxfish, or formed rows of closely connected bone plates, like seahorses.
Bone scales, like ganoid scales, are permanent, do not change and only increase annually in accordance with the growth of the fish, and distinct annual and seasonal marks remain on them. The winter layer has more frequent and thin layers than the summer one, so it is darker than the summer one. By the number of summer and winter layers on the scales, one can determine the age of some fish.
Under the scales, many fish have silvery crystals of guanine. Washed from scales, they are a valuable substance for obtaining artificial pearls. Glue is made from fish scales.
On the sides of the body of many fish, one can observe a number of prominent scales with holes that form the lateral line - one of the most important sense organs. The number of scales in the lateral line -
In the unicellular glands of the skin, pheromones are formed - volatile (odorous) substances released into the environment and affecting the receptors of other fish. They are specific to different species, even closely related ones; in some cases, their intraspecific differentiation (age, sex) was determined.
In many fish, including cyprinids, the so-called fear substance (ichthyopterin) is formed, which is released into the water from the body of a wounded individual and is perceived by its relatives as a signal announcing danger.
Fish skin regenerates quickly. Through it, on the one hand, a partial release of the end products of metabolism occurs, and on the other hand, the absorption of certain substances from the external environment (oxygen, carbonic acid, water, sulfur, phosphorus, calcium and other elements that play a large role in life). The skin also plays an important role as a receptor surface: thermo-, baro-, chemo- and other receptors are located in it.
In the thickness of the corium, the integumentary bones of the skull and pectoral fin belts are formed.
Through the muscle fibers of the myomers, connected to its inner surface, the skin participates in the work of the trunk and tail muscles.
Muscular system and electrical organs
The muscular system of fish, like other vertebrates, is divided into the muscular system of the body (somatic) and internal organs (visceral).
In the first, the muscles of the trunk, head and fins are isolated. Internal organs have their own muscles.
The muscular system is interconnected with the skeleton (support during contraction) and the nervous system (a nerve fiber approaches each muscle fiber, and each muscle is innervated by a specific nerve). Nerves, blood and lymphatic vessels are located in the connective tissue layer of muscles, which, unlike the muscles of mammals, is small,
In fish, like other vertebrates, the trunk muscles are most developed. It provides swimming fish. In real fish, it is represented by two large strands located along the body from head to tail (large lateral muscle - m. lateralis magnus) (Fig. 1). This muscle is divided by a longitudinal connective tissue layer into dorsal (upper) and abdominal (lower) parts.
Rice. 1 Musculature of bony fish (according to Kuznetsov, Chernov, 1972):
1 - myomers, 2 - myosepts
The lateral muscles are divided by myosepts into myomers, the number of which corresponds to the number of vertebrae. Myomeres are most clearly visible in fish larvae, while their bodies are transparent.
The muscles of the right and left sides, contracting alternately, bend the caudal section of the body and change the position of the caudal fin, due to which the body moves forward.
Above the large lateral muscle along the body between the shoulder girdle and tail in sturgeons and teleosts lies the rectus lateral superficial muscle (m. rectus lateralis, m. lateralis superficialis). In salmon, a lot of fat is deposited in it. The rectus abdominis (m. rectus abdominalis) stretches along the underside of the body; some fish, such as eels, do not. Between it and the direct lateral superficial muscle are oblique muscles (m. obliguus).
The muscle groups of the head control the movements of the jaw and gill apparatus (visceral muscles). The fins have their own muscles.
The largest accumulation of muscles also determines the location of the center of gravity of the body: in most fish it is located in the dorsal part.
The activity of the trunk muscles is regulated by the spinal cord and cerebellum, and the visceral muscles are innervated by the peripheral nervous system, which is excited involuntarily.
A distinction is made between striated (acting largely voluntarily) and smooth muscles (which act independently of the will of the animal). The striated muscles include the skeletal muscles of the body (trunk) and the muscles of the heart. Trunk muscles can contract quickly and strongly, but soon get tired. A feature of the structure of the heart muscles is not the parallel arrangement of isolated fibers, but the branching of their tips and the transition from one bundle to another, which determines the continuous operation of this organ.
Smooth muscles also consist of fibers, but much shorter and do not exhibit transverse striation. These are the muscles of the internal organs and the walls of blood vessels that have peripheral (sympathetic) innervation.
Striated fibers, and therefore muscles, are divided into red and white, which differ, as the name implies, in color. The color is due to the presence of myoglobin, a protein that readily binds oxygen. Myoglobin provides respiratory phosphorylation, accompanied by the release of a large amount of energy.
Red and white fibers are different in a number of morphophysiological characteristics: color, shape, mechanical and biochemical properties (respiratory rate, glycogen content, etc.).
Red muscle fibers (m. lateralis superficialis) - narrow, thin, intensively supplied with blood, located more superficially (in most species under the skin, along the body from head to tail), contain more myoglobin in the sarcoplasm;
accumulations of fat and glycogen were found in them. Their excitability is less, individual contractions last longer, but proceed more slowly; oxidative, phosphorus and carbohydrate metabolism is more intense than in whites.
The heart muscle (red) has little glycogen and a lot of enzymes of aerobic metabolism (oxidative metabolism). It is characterized by a moderate rate of contractions and tires more slowly than white muscles.
In wide, thicker, light white fibers m. lateralis magnus myoglobin is small, they have less glycogen and respiratory enzymes. Carbohydrate metabolism occurs predominantly anaerobically, and the amount of energy released is less. Individual cuts are fast. Muscles contract and fatigue faster than red ones. They lie deeper.
The red muscles are constantly active. They ensure long-term and uninterrupted functioning of the organs, support the constant movement of the pectoral fins, ensure the bending of the body when swimming and turning, and the continuous work of the heart.
With fast movement, throws, white muscles are active, with slow movement, red ones. Therefore, the presence of red or white fibers (muscles) depends on the mobility of the fish: "sprinters" have almost exclusively white muscles, in fish that are characterized by long migrations, in addition to the red lateral muscles, there are additional red fibers in the white muscles.
The bulk of the muscle tissue in fish is made up of white muscles. For example, in asp, roach, sabrefish, they account for 96.3; 95.2 and 94.9% respectively.
White and red muscles differ in chemical composition. Red muscles contain more fat, while white muscles contain more moisture and protein.
The thickness (diameter) of the muscle fiber varies depending on the type of fish, their age, size, lifestyle, and in pond fish - on the conditions of detention. For example, in a carp grown on natural food, the diameter of the muscle fiber is (µm): in fry - 5 ... 19, underyearlings - 14 ... 41, two-year-olds - 25 ... 50.
The trunk muscles form the bulk of fish meat. The yield of meat as a percentage of the total body weight (meatiness) is not the same in different species, and in individuals of the same species it varies depending on sex, conditions of detention, etc.
Fish meat is digested faster than the meat of warm-blooded animals. It is often colorless (perch) or has shades (orange in salmon, yellowish in sturgeon, etc.), depending on the presence of various fats and carotenoids.
The bulk of fish muscle proteins are albumins and globulins (85%), in total, 4 ... 7 protein fractions are isolated from different fish.
The chemical composition of meat (water, fats, proteins, minerals) is different not only in different species, but also in different parts of the body. In fish of the same species, the amount and chemical composition of meat depend on the nutritional conditions and the physiological state of the fish.
During the spawning period, especially in migratory fish, reserve substances are consumed, depletion is observed and, as a result, the amount of fat decreases and the quality of meat deteriorates. In chum salmon, for example, during the approach to spawning grounds, the relative mass of bones increases by 1.5 times, skin - by 2.5 times. Muscles are hydrated - the dry matter content is reduced by more than two times; fat and nitrogenous substances practically disappear from the muscles - the fish loses up to 98.4% of fat and 57% of protein.
Features of the environment (primarily food and water) can greatly change the nutritional value of fish: in swampy, muddy or oil-polluted water bodies, fish have meat with an unpleasant odor. The quality of meat also depends on the diameter of the muscle fiber, as well as the amount of fat in the muscles. To a large extent, it is determined by the ratio of the mass of muscle and connective tissues, which can be used to judge the content of full-fledged muscle proteins in the muscles (compared to defective proteins of the connective tissue layer). This ratio varies depending on the physiological state of the fish and environmental factors. In the muscle proteins of bony fish, proteins account for: sarcoplasms 20 ... 30%, myofibrils - 60 ... 70, stroma - about 2%.
All the variety of body movements is provided by the work of the muscular system. It mainly provides the release of heat and electricity in the body of the fish. An electric current is formed when a nerve impulse is conducted along a nerve, with a contraction of myofibrils, irritation of photosensitive cells, mechanochemoreceptors, etc.
Electric Organs