Possibilities of raising migratory fish in brackish water. Physiology and ecology of fish Types of commercial fish
Of the 40-41 thousand species of vertebrates that exist on earth, fish is the richest group of species: v it has over 20 thousand living representatives. Such a large number of species is explained, first of all, by the fact that fish - 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 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 high-mountain 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 bodies of water.
Of the 20 thousand species of fish, 11.6 thousand are marine, 8.3 thousand are freshwater, and the rest are migratory. All fish belonging to a number of fish, on the basis of their similarity and kinship, are divided according to the scheme developed by the Soviet academician L. S. Berg into two classes: cartilage 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 signs that reflect its adaptability to certain conditions. All individuals of the species can interbreed and produce offspring. Each species in the development process has adapted to the known conditions of reproduction and nutrition, temperature and gas conditions, and other factors of the aquatic environment.
The body shape 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, arrow-shaped, ribbon-shaped, acne, flat and spherical.
The body of the fish is covered with skin, which has an upper layer - the epidermis and a lower layer - the corium. The epidermis consists of a large number of epithelial cells; in this layer are mucus-releasing, pigmented, luminous and poisonous glands. Corium, or the skin itself, is a connective tissue penetrated by blood vessels and nerves. There are also clusters of large pigment cells and guanine crystals, which give the skin of fish a silver color.
In most fish, the body is covered with scales. It is not in fish swimming at low speeds. Scales ensure smoothness of the surface of the body and prevents the occurrence of skin folds on the sides.
Freshwater fish have bone scales. By the nature of the surface, two types of bone scales are distinguished: cycloid with a smooth posterior edge (cyprinids, herring) and ctenoid, whose posterior edge is armed with spines (perches). According to the annual rings of bone scales, the age of bony fish is determined (Fig. 2).
The age of the fish is also determined by the bones (bones of the gill cover, jawbone, large integumentary bone of the humeral girdle-clementrum, sections of hard and soft rays of the fins, etc.) and otoliths (calcareous formations in the ear capsule), where, like on the scales, they form stratifications corresponding to annual life cycles.
The body of sturgeon fish is covered with a special kind 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).
Fins of fish are: paired - pectoral, ventral and unpaired - dorsal, anal, caudal. The dorsal fin can be one (for cyprinids), two (for perches) and three (for cods). The fat fin without bone rays is a soft skin outgrowth on the back of the back (in salmonids). The fins balance the body of the fish and move it in different directions. The tail fin creates a driving force and acts as a rudder, ensuring the maneuverability of the fish when cornering. The dorsal and anal fins maintain a normal position, the body of the fish, that is, they act as a keel. Paired fins maintain balance and are the 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, a fish swallows water with its mouth and pushes it out through its 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 bodies of water, where oxygen is often lacking, can breathe in the skin. In some fish, the swim bladder, intestines, and special supplemental organs are able to use atmospheric oxygen. So, snakeheads, basking in shallow water, can breathe air through the suprajugal organ. The circulatory system of fish consists of the heart and blood vessels. Their heart is two-chamber (it has only the atrium and ventricle), directs venous blood through the abdominal aorta to the gills. The most powerful blood vessels pass along the spine. Fish only have one blood circulation. The digestive organs of fish are the mouth, pharynx, esophagus, stomach, liver, intestines, ending in the anus.
The mouth shape of fish is diverse. Plankton-eating fish have an upper mouth, feeding at the bottom — a lower mouth, and in predatory fish — an ending mouth. Many fish have teeth. Carp fish have pharyngeal teeth. A fish's mouth is located behind the mouth, where food initially enters, then it is sent to the pharynx, esophagus, and stomach, where it begins to be digested by 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. In carp fish, there is no stomach, and food is digested in the intestines. Undigested food debris is discharged into the hind gut and removed through the anus.
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 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 the final metabolic products from the body).
The nervous system is divided into the central, which includes the brain and spinal cord, and peripheral - the nerves that extend from the brain and spinal cord. Nerve fibers depart from the brain, the ends of which extend to the surface of the skin and form in most fish a pronounced lateral line extending from the head to the beginning of the rays of the caudal fin. The lateral line serves to orient the fish: determining 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, so the fish are shortsighted: most of them distinguish objects at a distance of 1 m, and a maximum of 1 see no more than 10-15 m.
The nostrils are located in front of each eye, leading into a blind olfactory sac.
The organ of hearing of fish is at the same time an organ of balance, it is located in the back of the skull, cartilage, or bone chamber: it consists of the upper and lower sacs, in which the otoliths are located - stones made up of calcium compounds.
The taste organs in the form of microscopic taste cells are located in the shell of the oral cavity and on the entire surface of the body. In fish, the sense of touch is well developed.
The genitals in females are the ovaries (testicles), 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 high-value food product. The highest food quality is characterized by caviar of sturgeon and salmon fish.
The hydrostatic organ that provides fish buoyancy is a swimming bladder filled with a mixture of gases and located above the insides. Some bottom fish have no swim bladder.
The temperature sensation of fish is associated with receptors located in the skin. The simplest reaction of fish to changes in water temperature is to move to places where the temperature is more favorable for them. Fish do not have thermoregulation mechanisms, their body temperature is unstable and corresponds to the temperature of the water or very slightly differs from it.
Fish and the environment
Not only various types of fish live in water, only different types of fish, but also thousands of living things, plants and microscopic organisms. The reservoirs where the fish live differ in physicochemical properties. All these factors affect the biological processes in the water and, therefore, the life of fish.
The relationship of fish with the external environment is combined into two groups of factors: abiotic and biotic.
Biotic factors include the world of animals and plant organisms surrounding the fish in water and acting on it. This also includes intraspecific and interspecific relations of fish.
The physical and chemical properties of water (temperature, salinity, gas content, etc.) acting on 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 on the body of human economic activity. Land reclamation enhances the productivity of water bodies, and 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 taking place in water, and, consequently, on 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 Lucania fish lives in warm springs at a water temperature of + 50 ° C and above, and crucian carp spends 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, the development of eggs, growth rate, gas exchange, digestion.
Oxygen consumption is directly dependent on the temperature of the water: when it decreases, oxygen consumption decreases, and when it increases, it increases. Water temperature also affects fish nutrition. With its increase, the rate of digestion of food in fish increases, and vice versa. So, carp feeds most intensively at a water temperature of +23 ... + 29 ° С, and at +15 ... + 17 ° С it reduces its nutrition by three to four times. Therefore, in pond farms constantly monitor the temperature of the water. In fish farming, pools are widely used in thermal and nuclear power plants, underground thermal waters, warm sea currents, etc.
The fish of our reservoirs and seas are divided into thermophilic (cyprinidae, sturgeon, catfish, acne) and cold-loving (cod and salmon). In the water bodies of Kazakhstan, thermophilic fish live mainly, except for farmed 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.) are concentrated in winter in areas of the deep zone defined for each species, they show passivity, their nutrition slows down or completely stops.
Fishes that lead an active lifestyle in winter (salmon, whitefish, pike perch, etc.) are cold-loving.
The distribution of commercial fish in large bodies of water usually depends on temperature in different areas of the body of water. It is used for fishing and fishing exploration.
Water salinity also affects fish, although most of them withstand its fluctuations. The salinity of the water is determined in thousandths: 1 ppm is equal to 1 g of dissolved salts in 1 l of sea water, and it is indicated by знаком. Some fish species withstand water salinity up to 70 ‰, i.e. 70 g / l.
In terms of habitat and in relation to salinity, fish waters are usually divided into four groups: marine, freshwater, migratory and brackish-water.
Marine species include fish living in oceans and coastal marine waters. Freshwater fish constantly live in fresh water. Passing fish for breeding go either from sea water to fresh (salmon, herring, sturgeon), or from fresh water to sea (some eels). Brackish-water fish live in desalinated areas of the seas and inland seas with low salinity.
For fish living in lake ponds, ponds and rivers, the importance of 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 cyprinids it should be 5-8, for salmon - 8-11 mg / l. With a decrease in oxygen concentration to 3 mg / l, carp feels bad and eats worse, and at 1.2-0.6 mg / l it can die. With shallowing of the lake, with an increase in water temperature and with its overgrowing with vegetation, the oxygen regime deteriorates. In shallow reservoirs, when their surface is covered with a dense layer of ice and snow in winter, atmospheric oxygen stops and after some time, usually in March (if not made an ice hole), the death, or the so-called “freezing” of fish, begins from oxygen starvation.
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 carbon dioxide content in the water depends on the time of year and the depth of the reservoir. In the summer, when water plants absorb carbon dioxide, it is very small in water. High concentrations of carbon dioxide are harmful to fish. When the content of free carbon dioxide is 30 mg / l, the fish eats less intensely, its growth slows down.
Hydrogen sulfide formed in water in the absence of oxygen and causes the death of fish, and its strength depends on the temperature of the water. At high water temperatures, fish from hydrogen sulfide quickly dies.
With overgrowing of water bodies and decay of aquatic vegetation in water, the concentration of dissolved organic substances increases and the color of the water changes. In swamped water bodies (brown color of water), fish cannot live at all.
Transparency - one of the important indicators of the physical properties of water. In clean lakes, photosynthesis of plants proceeds at a depth of 10-20 m, in reservoirs with opaque water - at a depth of 4-5 m, and in ponds in summer, the transparency does not exceed 40-60 cm.
The degree of transparency of water depends on several 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 flowering water. In any case, a decrease in water transparency is associated with the presence of the smallest suspended mineral and organic particles. Once in the gills of the fish, they make it difficult for them to breathe and breathe.
Pure water is a chemically neutral compound equally with both acidic and alkaline properties. Ions of hydrogen and hydroxyl are present in it in equal amounts. Based on this property of pure water, the concentration of hydrogen ions is determined in pond farms; for this purpose, the pH value of water is established. When the pH is 7, this corresponds to a neutral state of water, less than a 7-acid state, and above a 7-alkaline state.
In most fresh water bodies, the pH is 6.5-8.5. In summer, with intense photosynthesis, an increase in pH to 9 and above is observed. In winter, with the accumulation of carbon dioxide under ice, its lower values \u200b\u200bare observed; pH changes during the day.
In pond and lake commodity fish farming, regular monitoring of water quality is established: water pH, color, transparency and its temperature are determined. Each fish farm for conducting hydrochemical analysis of water 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 fish species mutually exist, which differ from each other in the nature of their nutrition, 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 relationships of fish are aimed at ensuring the existence of the species through the formation of single species groups: schools, elementary populations, accumulations, etc.
Many fish lead pack image life (Atlantic herring, hamsa, etc.), and most fish gather in schools 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 a unity of behavior. Flocking - the adaptation of fish to search for food, find migration routes, protection from predators. A school of fish is often called a school. However, there are some species that are not collected in flocks (catfish, many sharks, pinagoras, etc.).
The elementary population is a group of fish of basically the same age, similar in physiological state (fatness, puberty, the amount of hemoglobin in the blood, etc.) and lasts 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, self-reproducing group of fish that inhabits a certain area and is attached to specific breeding, feeding and wintering sites.
Accumulation is a temporary association of several schools and elementary fish populations resulting from a number of reasons. These include clusters:
spawning, arising for breeding, consisting almost exclusively of sexually mature individuals;
migratory, arising on the ways of fish movement for spawning, feeding or wintering;
feeding, formed on the ground feeding fish and caused mainly by the concentration of food objects;
wintering occurring in places of wintering of fish.
Colonies are formed as temporary protective groups of fish, usually consisting of individuals of the same sex. They are formed at breeding sites to protect the clutch of eggs 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 became larger in Bukhtarma, Kapchagai, Chardara, and other reservoirs than they were in the former lake. Zaysan, the Balkhash-Ili basin and in 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 amount of carp is reduced, and vice versa.
Between individual fish species there is competition over 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 serving as food for them decreases and, at the same time, the pedigree quality of predators deteriorates, they are forced to switch to cannibalism, i.e. they eat individuals of their species and even their descendants.
Fish nutrition is different, depending on their species, age, and also time of year.
Feed planktonic and benthic organisms serve for fish.
Plankton from Greek planktos - soaring - is a combination of plant and animal organisms that live in water. They are completely devoid of motion organs, or they have weak motion organs that cannot withstand the movement of water. Plankton is divided into three groups: zooplankton - animal organisms represented by various invertebrates; phytoplankton - plant organisms represented by a variety of algae, and bacterioplankton occupies a special place (Figs. 4 and 5).
Planktonic organisms, as a rule, are small in size and have a low density, which helps them swim 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 fed by adult planktonivorous fish. Zooplankton has high nutritional qualities. So, in Daphnia, 58% of protein and 6.5% of fat are contained in the dry matter of the body, and in Cyclops - 66.8% of protein and 19.8% of fat.
The population of the bottom of the reservoir is called benthos, from Greek benthos - depth (Fig. 6 and 7). Benthic organisms are represented by diverse and numerous plants (phyto-benthos) and animals (zoobenthos).
By the nature of nutrition fish of inland waters are divided into:
1. Herbivores, who eat mostly 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 intestinal, mollusks, eggs and invertebrate larvae, etc .;
benthophages that feed on organisms that live on the ground and in the ground of the bottom of water bodies.
3. Ichthyophages, or carnivores, which feed on fish, vertebrates (frogs, waterfowl, etc.).
However, such a division is conditional.
Many fish have a mixed diet. For example, carp is omnivorous, feeds on both plant and animal feed.
Fish are different and by the nature of the laying of eggs during the spawning period. The following environmental groups are distinguished here;
lithophiles - breed on stony ground, usually in rivers, in the course (sturgeon, salmon, etc.);
phytophiles - multiply among plants, lay eggs on vegetating 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 - spawn eggs in the water column, where it develops (grass carp, silver carp, herring, etc.);
ostracophiles - lay eggs inside
mantle cavity of mollusks and sometimes under the shell of crabs and other animals (mustard).
Fish are in a complex relationship with each other, life and their growth depend on the state of water bodies, on the biological and biochemical processes in the water. For the artificial breeding of fish in water bodies and for the organization of commercial fish farming, it is necessary to study well the available water bodies and ponds, to know the biology of fish. Fish farming activities carried out without knowledge of the business can only be harmful. Therefore, fishery enterprises, state farms, and collective farms must have experienced fish farmers and ichthyologists.
Optimum development temperatures can be determined by assessing the intensity of metabolic processes at individual stages (under 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 optimum temperature.
Factors affecting the incubation process, and the possibility of their regulation.
Of all abiotic factors, the strongest effect on fish is temperature. Temperature has a very large effect on embryogenesis of fish at all stages and stages of embryo development. Moreover, for each stage of embryo development, there is an optimum temperature. Optimum should be understood as such temperatures,at which the highest metabolic rate (metabolism) is observed at certain stages without disturbing morphogenesis. The temperature conditions under which embryonic development takes place under natural conditions and with existing methods of eggs incubation almost never correspond to the maximum manifestation of valuable species traits of fish that are useful (necessary) for humans.
Methods for determining the optimal temperature conditions for development in fish embryos are quite complex
It was established that in the process of development, the optimum temperature for spring-spawning fish rises, for autumn-spawning, it decreases.
The size of the zone of optimal temperatures with the development of the embryo expands and reaches its largest size before hatching.
Determination of optimal temperature conditions of development allows not only to improve the incubation technique (keeping of larvae, growing larvae and growing young), but also opens up the possibility of developing techniques and methods for directing influence on development processes, obtaining embryos with given morphofunctional properties and given sizes.
Consider the effect on the incubation of eggs of other abiotic factors.
The development of fish embryos occurs with constant consumption of oxygen from the environment and the release of carbon dioxide. A constant product of embryo excretion is ammonia, which occurs in the body during the breakdown of proteins.
Oxygen. The ranges of oxygen concentrations, within which embryos of different species of fish can develop, vary significantly, and the oxygen concentrations corresponding to the upper boundaries of these ranges are much higher than those found in nature. So, for pike perch, the minimum and maximum concentration of oxygen, at which embryos still develop and hatching of prelarvae, are 2.0 and 42.2 mg / l, respectively.
It has been established that with an increase in oxygen content in the range from the lower lethal border to values \u200b\u200bsignificantly exceeding its natural content, the rate of development of embryos naturally increases.
In conditions of lack or excess of oxygen concentrations in embryos, large differences in the nature of morphofunctional changes are observed. So, at low oxygen concentrations the most typical anomalies are expressed in deformation of the body and disproportionate development and even the absence of separate organs, the appearance of hemorrhages in the region of large vessels, the formation of dropsy on the body and gall sac. At elevated oxygen concentrationsthe most characteristic morphological disturbance in embryos is a sharp weakening or even complete suppression of red blood cell formation. So, in pike embryos developed at an oxygen concentration of 42-45 mg / l, by the end of embryogenesis, red blood cells in the bloodstream completely disappear.
Along with the absence of red blood cells, other significant defects are also observed: muscle motility ceases, the ability to react to external irritations and to get rid of the membranes is lost.
In general, embryos incubated at various oxygen concentrations differ significantly in their degree of development upon hatching
Carbon dioxide (CO).The development of embryos is possible in a very wide range of CO concentrations, and the concentration values \u200b\u200bcorresponding to the upper boundaries of these ranges far exceed those that embryos encounter in natural conditions. But with an excess of carbon dioxide in water, the number of normally developing embryos decreases. It was proved in experiments that an increase in the concentration of dioxide in water from 6.5 to 203.0 mg / L causes a decrease in the survival of chum embryos from 86% to 2%, and when the concentration of carbon dioxide is up to 243 mg / L, all embryos during incubation perished.
It was also established that the embryos of bream and other species of cyprinids (roach, blue bream, silver bream) normally develop when the concentration of carbon dioxide is 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 suggests that carbon dioxide is a necessary component of development. The role of carbon dioxide in fish embryogenesis is diverse. An increase in its concentration (within normal limits) in water enhances muscle motility and its presence in the environment is necessary to maintain the level of motor activity of the embryos, it decomposes the embryo's oxyhemoglobin and thereby ensures the necessary tension in the tissues, it is necessary for the formation of organic compounds of the body.
Ammoniain bony fishes, it is the main product of nitrogen 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 NH ammonium ions. The ratio between the number of these forms depends significantly on temperature and pH. With increasing temperature and pH, the amount of NH sharply increases. The toxic effect on fish is predominantly NH. The effect of NH has a negative effect on fish embryos. For example, in trout and salmon embryos, ammonia causes a disturbance in 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 body weight of pink salmon embryos. At the same time, it must be borne in mind that ammonia in bony fishes can be re-involved in metabolic reactions and the formation of non-toxic products.
Hydrogen pH of water,in which embryos develop, should be close to the neutral level - 6.5-7.5.
Water requirements.Before the water is supplied to the incubation apparatus, it must be cleaned and neutralized using sedimentation tanks, coarse and fine filters, and bactericidal plants. The development of embryos can be adversely affected by the brass mesh used in the hatching apparatus, as well as fresh wood. This effect is especially evident if sufficient flow is not provided. The impact of the brass grid (more precisely, copper and zinc ions) causes inhibition of growth and development, reduces the viability of embryos. Exposure to substances extracted from wood leads to dropsy and anomalies in the development of various organs.
Water flow rate.For the normal development of embryos, water flow is necessary. Lack of flow or its insufficiency have the same effect on embryos as lack of oxygen and excess carbon dioxide. If there is no water change at the surface of the embryos, the diffusion of oxygen and carbon dioxide through the shell does not provide the necessary gas exchange rate and the embryos lack oxygen. Despite the normal saturation of 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. Effective water exchange during incubation of eggs in a stationary state (salmon roe) is created when water is circulated perpendicular to the plane of the frames with caviar - from bottom to top with an intensity in the range of 0.6-1.6 cm / sec. This condition is fully met by the MI incubation apparatus simulating the conditions of water exchange in natural spawning nests.
For incubation of Beluga and Stellate sturgeon embryos, water consumption in the range of 100-500 and 50-250 ml per embryo per day, respectively, is considered optimal. Before hatching, the larvae in the incubation apparatus increase water consumption in order to ensure normal conditions of gas exchange and removal of the products of matabolism.
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 is reduced and the growth of juveniles is accelerated, but overripe caviar also develops, which dies in fresh water. The increased resistance of embryos developing in brackish water to mechanical stresses was also noted. Therefore, in recent years, the question of the possibility of raising migratory fish in brackish water from the very beginning of their development has been gaining great importance.
The influence of light. When conducting incubation, it is necessary to take into account the adaptability of embryos and larvae of various fish species to lighting. For example, light is destructive for salmon embryos, so hatcheries must be dimmed. Incubation of sturgeon caviar in complete darkness, on the contrary, leads to a delay in development. Exposure to direct sunlight inhibits the growth and development of sturgeon embryos and reduces the viability of the larvae. 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, in the artificial reproduction of sturgeon, incubation apparatus should be protected from direct sunlight, as it can cause damage to embryos and the appearance of freaks.
Care for eggs during incubation.
Before the start of the fish breeding cycle, all incubation apparatus must be repaired and disinfected with a solution of bleach, washed with water, and the walls and floor should be washed with 10% lime solution (milk). For prophylactic purposes against caviar damage by saprolegnia, it must be treated with a 0.5% formalin solution for 30-60 seconds before loading into the incubation apparatus.
Care for eggs during the incubation period consists in monitoring the temperature, concentration of oxygen, carbon dioxide, pH, flow rate, water level, light mode, and the state of the embryos; selection of dead embryos (with special tweezers, screens, pears, siphon); preventative treatment as needed. Dead eggs are whitish. When silting salmon caviar is carried out strangulation. The soul and selection of dead embryos should be carried out during periods of reduced sensitivity.
Duration and features of the incubation of eggs of various fish species. Hatching of larvae in various incubation apparatuses.
The duration of the incubation of eggs largely depends on the temperature of the water. Usually, with a gradual increase in water temperature within the optimal limits for embryogenesis of one species or another, the development of the embryo gradually accelerates, but as it approaches the maximum temperature, the rate of development increases less. At temperatures close to the upper threshold, in the early stages of crushing of fertilized eggs, its embryogenesis slows down, despite an increase in temperature, and with a greater increase, the death of eggs occurs.
Under adverse conditions (insufficient flow rate, overloading of incubation apparatus, etc.), the development of incubated eggs slows down, hatching begins late and takes longer. The difference in the duration of development at the same water temperature and different flow rates and loading can reach 1/3 of the incubation period.
Features incubation of eggs of various species of fish. (sturgeon and salmon).
Sturgeon .:supply of incubation apparatus with water with 100% oxygen saturation, carbon dioxide concentration of not more than 10 mg / l, pH - 6.5-7.5; protection from direct sunlight to prevent damage to embryos and the appearance of freaks.
For stellate sturgeon, the optimum temperature is from 14 to 25 ° C, at a temperature of 29 ° C, the development of embryos is inhibited, at 12 ° C - a great death and many freaks appear.
The optimal incubation temperature for Beluga spring course 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-like.The optimum oxygen level at the optimum temperature for salmonids is 100% of saturation, the level of dioxide is not more than 10 mg / l (for pink salmon it is permissible no more than 15, chum salmon no more than 20 mg / l), pH - 6.5-7.5; complete blackout during incubation of salmon caviar, protection from direct sunlight of whitefish caviar.
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 caviarmainly 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 variable and depends not only on temperature, gas exchange, other incubation conditions, but also on specific conditions (flow rate in the incubation apparatus, shocks, etc.) necessary for the isolation of the embryo hatching enzyme from the shells. The worse the conditions, the longer the hatching time.
Usually, under normal environmental conditions, hatching of viable larvae from one batch of eggs is completed in sturgeons within a few hours to 1.5 days, in salmonids - 3-5 days. The moment when there are already several tens of larvae in the incubation apparatus can be considered the beginning of the hatching period. Usually, mass hatching occurs after this, and at the end of hatching, dead and ugly embryos remain in the shells of the apparatus.
The extended hatching periods most often indicate adverse environmental conditions and lead to an increase in the diversity of prelarvae and an increase in their mortality. The length of hatching is a great inconvenience for the farmer, so it is important to know the following.
The hatching of the embryo from the eggs largely depends 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 increases sharply, and the activity of the gland decreases. The strength of the membranes with the advent of the enzyme in perivitelin fluid rapidly decreases. Moving in weakened shells, the embryo breaks them, goes into the water and becomes a larva. Isolation of the hatching enzyme and muscle activity, which is of paramount importance for release from the shells, is more dependent on external conditions. They are stimulated by improved aeration conditions, water movement, tremors. To ensure friendly hatching, for example, in sturgeons, it is necessary: \u200b\u200bstrong flowing and vigorous mixing of eggs in the incubation apparatus.
The hatching dates of the larvae also depend on the design of the incubation apparatus. So, in sturgeons, the most favorable conditions for friendly hatching are created in the sturgeon incubator, in Yushchenko’s apparatuses the hatching of larvae is significantly stretched and even less favorable conditions for hatching are in the tray incubation apparatuses of Sadov and Kakhanskaya.
TOPIC. BIOLOGICAL BASES OF EXTENDING PROBLEMS, GROWING LARVAS AND GROWING YOUNG FISH.
The choice of fish breeding equipment depending on the ecological and physiological properties of the species.
In the modern technological process of plant reproduction of fish, following incubation of eggs, aging of prelarvae, growth of larvae and rearing of juveniles begin. 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 sturgeons and salmonids, 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 technologies associated with the lack of correct ideas about the particular features of the biology of the bred object or the mechanical use of fish breeding equipment and regimes, without understanding the biological meaning, entail an increased death of farmed fish during early ontogenesis.
One of the most critical periods of the entire biotechnological process of artificial reproduction of fish is the maintenance of prelarvae and the growth of larvae.
Freed from the shells of the prelarvae pass in their development stage of the passive state, which is characterized by low mobility. When maintaining the prelarvae, the adaptive features of this period of development of this species are taken into account, and conditions are created that ensure the greatest survival before switching to active nutrition. With the transition to active (exogenous) nutrition, the next link in the fish-breeding process begins - the growth of larvae.
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PHYSIOLOGY AND ECOLOGY OF FISH
The sensory organs are represented in fish on the head. eyes and holes olfactory capsules.
Almost all fish distinguish colors, and some species can reflex change your color: Light stimuli are converted by the organs of vision into nerve impulses that enter the skin pigment cells.
Fish recognize well smells and availability flavors in water; in many species, taste buds are located not only in the oral cavity and on the lips, but also on various antennae and skin outgrowths around the mouth.
On the head of the fish are seismic sensor channels and electrosensitive organs that allow them to navigate in the dark or muddy water according to the slightest changes in the electric field. They make up the sensory system side line. In many species, the lateral line is clearly visible as one or more chains of scales with small holes.
Fish do not have external hearing organs (auditory apertures or auricles), but well developed inner ear allows them to hear sounds.
Fish breathing carried through rich blood vessels gills (gill lobes), and some species (loach) developed devices for additional breathing of atmospheric air with a deficiency of oxygen in the water (during cold, high temperature, etc.). Loaches swallow air, which then enters the bloodstream through the blood vessels and capillaries of the internal organs.
Fish movements very diverse. Usually fish move with wave-like body bends.
Fish with a serpentine body shape (lamprey, eel, loach) move with whole body bends. The speed of their movement is small (figure on the left):
(shows changes in body position at certain intervals of time)
Body temperature in fish it is determined by the temperature of their surrounding water.
In relation to water temperature, fish are divided into cold-loving (cold-water) and heat-loving (warm-water). Some species feel great under the ice of the Arctic, and some species can freeze in ice for several months. Tench and crucian carp freeze water bodies to the bottom. A number of species that quietly tolerate freezing of the surface of a reservoir are not able to reproduce if in summer the water does not warm up to a temperature of 15-20 ° C (catfish, silver carp, carp).
For most cold-water species (whitefish, trout), a water temperature of more than 20 ° C is unacceptable, since oxygen content in warm water for these fish is not enough. It is known that the solubility of gases, including oxygen, in water decreases sharply with increasing temperature. Some species easily tolerate oxygen deficiency in water in a wide temperature range (crucian carp, tench), while others live only in the cold and oxygen-rich water of mountain rivers (grayling, trout).
Fish coloring may be the most diverse. In almost all cases, the color of the fish plays either concealer (from predators), or signaling (in pack species) role. The color of the fish varies depending on the season, habitat and physiological condition; most clearly, many fish species are colored during the breeding season.
There is a concept marriage coloring(mating outfit) fish. During the breeding season, in some species (roach, bream), “pearl” tubercles appear on the scales and scalp.
Fish migrations
Migrations most fish are associated with the change of water bodies, differing in salinity.
Towards salinity of water all fish can be divided into three groups: marine (live at salinity close to oceanic) freshwater (do not tolerate salinization) and brackish waterfound both in the estuarine areas of the sea, and in the lower reaches of the rivers. The latter species are close to those walking in brackish-water deltas, lips and estuaries, and spawning in rivers and floodplain lakes.
Verily freshwater fish are fish that live and breed only in fresh water (gudgeon).
A number of species, usually living in sea or fresh water, can easily pass under the new conditions to "atypical" water for themselves. So, some gobies and sea needles spread along the rivers and reservoirs of our southern rivers.
Separate group form migratory fishspending most of their life in the sea (walking and ripening, i.e. growing in the sea), and on spawning coming to rivers or, conversely, i.e. spawning migrations from rivers to seas.
These fish include many commercially valuable sturgeon and salmon fish. Some types of fish (salmon) return to those reservoirs where they were born (this phenomenon is called homing - the instinct of the house). These abilities of salmon are actively used in introducing caviar into rivers new to these fish. The mechanisms that allow migratory fishes to unmistakably find their native river or lake are unknown.
There are species that live most of the life in rivers, and go to sea for spawning (i.e. vice versa) Among our fauna, such trips are made by river eel, living and ripening in rivers and lakes, and to continue the genus, leaving for the Atlantic Ocean.
In migratory fish, when passing from one medium to another, it is noticeable metabolism (most often when they mature sex products they stop eating) and appearance (body shape, color, etc.). Often these changes are irreversible - many species after spawning die.
On our site you can also get acquainted with general information about fish in Russia: introduction, external structure of fish, physiology and ecology of fish, fish farming, protection of fish resources and aquarium studies, glossary of terms on ichthyology, literature on fish in Russia and the USSR.
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Our author’s methodological materials on ichthyology and fish in Russia: Computer digital (for PC-Windows) identifier, In addition, on our website you can purchase teaching materials in aquatic ecology and hydrobiology: Computer digital (for PC-Windows) identifiers:,,, |
Feed fish. Widespread off the coast of Europe. The 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). It is rare in the waters of Russia. There are no subspecies. The taxon, originally described as Alosa alosa bulgarica from the southwestern part of the Black Sea (Svetovidov, 1952), is now regarded as A. caspia bulgarica (Marinov, 1964; Svetovidov, 1973). The Macedonian subspecies A. alosa macedónica (Svetovidov, 1973) now stands out as an independent species Alosa macedónica Vinciguerra, 1921 (Economidis, 1974; Hoestlandt, 1991). Included in the IUCN Red List. It is the subject of fishing. [...]
Passing fish, unlike impassable, should be able to easily switch from the "freshwater" method of osmo, regulation to "sea" when moving from fresh water to sea, and vice versa, when moving in the opposite direction. [...]
Passing fish dramatically change their habitat (marine environment to freshwater and vice versa), overcome huge distances (salmon travels 1100-2500 km at a speed of 50-100 km per day), overcome significant rapids, waterfalls. [...]
Feed fish. They move for spawning (spawning) either from sea water to fresh (salmon, herring, sturgeon), or from fresh to sea (eels, etc.). [...]
Passing and freshwater view. It lives in the basins of the Barents, White, Baltic, Black, Caspian and Aral seas. Six subspecies were noted, of which 4 passing and 1 lacustrine inhabit the waters of Russia. Passing fish of Northern Europe, in Russia in the basins of the Baltic, White and Barents seas to Pechora. Freshwater river (trout) and lake (trout) forms are ubiquitous in the basins of these seas. Object of fishing and fish farming. Baltic populations are sharply declining. Scheduled for entry in the Red Book of Russia. [...]
Passing 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. Spawns in the rivers of Japan and the Kuril Islands, Primorye and Sakhalin. It is an important subject of fishing. [...]
Passing fish of the Black and Azov Seas. It enters the 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 provide a description for them. Valuable commercial species. It is included in the IUCN Red List by category DD (IUCN Red list ..., 1996). [...]
In migratory fish moving for spawning from rivers to seas and back, the osmotic pressure undergoes changes, although insignificant. Upon transition from seawater to fresh water, these fishes almost completely cease water intake through the intestine as a result of degeneration of its mucous membranes (see below, the chapter on migrations). [...]
Many migratory fish and cyclostomes feed on the sea, and for breeding enter rivers, making anadromous migrations. Anadromous migrations are characteristic of lampreys, sturgeon, salmon, some herring, cyprinids, etc. Some migratory fish feed in rivers, and go to sea for spawning, making metadromic migrations - such is eel, etc. [...]
Salmon is a migratory fish. Young live in fresh water for 2 to 5 years, eat insects, then slide into the sea and become predatory fish. The usual place for a salmon to lodge is the Baltic Sea. Some juveniles remain in the Gulf of Bothnia and the Gulf of Finland. For example, in the Soviet Union, artificially diluted salmon do not leave the waters of the Gulf of Finland. In two years at sea, salmon reaches 3-5 kilograms. It feeds mainly on herring, sprat, gerbil. Having reached puberty, salmon goes to the river where he was born. He finds the river, the place of his spawning grounds, by the smell of water. [...]
Berg L.S. Pisces of the USSR and neighboring countries. Berg L. S. Spring and winter races in migratory fish, "Essays on the general issues of ichthyology." Jad. Academy of Sciences of the USSR, 1953, p. 242-260. [...]
Lamprey is a migratory fish found in the lower Volga and in the channels of the delta, even in its coastal part. Currently very small. Leads a hidden lifestyle. It spawns from March to May in a strong current in places with rocky or sandbanks or in pits. The first larvae appear in May. Like adults, they lead a hidden lifestyle, burrowing in silt or sand. Caught very rarely. [...]
Movement of migratory fish mainly of the Northern Hemisphere (salmon, sturgeon, etc.) from the seas to rivers for spawning. [...]
L.S. Berg. Freshwater fish of Russia. C. 2 p. II and. Definitive tables of marine and migratory fish of Europe. [...]
Stellate sturgeon is a migratory fish that lives in the basins of the Caspian, Azov and Black Seas. It spawns into the Ural, Volga, Kuru and other rivers. This is a numerous valuable commercial fish, reaching a length of about 2.2 m and a mass of 6-8 kg (average fishing mass of 7-8 kg). Females of stellate sturgeon reach puberty at 12-17 years old, males at 9-12 years old. Fertility of females is 20-400 thousand eggs. Spawning runs from May to August. The duration of incubation of eggs at 23 ° C for about 2-3 days. Juveniles slide into the sea at the age of 2-3 months. [...]
Caspian migratory fish spawn in the rivers Volga, Ural »Kure. But the Volga and Kura are regulated by cascades of waterworks and many spawning grounds were inaccessible to fish. Only the lower river. The Urals were left free from the construction of waterworks to preserve 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 Aral "basins" of the Caspian and Black Sea. A thorn is a migratory fish, it spawns into rivers for spawning, there are also "residential" tenon forms "that do not leave the river for several years" probably "before puberty. [...]
Most fish during river migration usually stop feeding or eat less intensively than at sea, and the huge expenditure of energy naturally requires the consumption of nutrients accumulated during feeding in the sea. That’s why most migratory fish, as they move up’s along the river, experience severe depletion. [...]
As a rule, fish have constant feeding places ("fat"). Some fish constantly live, breed and hibernate in areas rich in food, others make significant movements to places of feeding (feeding migrations), spawning (spawning migrations) or to places of wintering (wintering migrations). In accordance with this, the fish are divided into settled (or tuvodny), passing and semi-passage. Passing fish make long trips either from the seas, where they spend most of their lives, to places of spawning in rivers (chum, salmon, whitefish, nelma), or from the rivers in which they live, go to sea (eel). [. ..]
However, the presence of migratory fish in the subtropics, tropics, and equatorial zone indicates that it was not the reason for the emergence of migratory fish. The transition of sea or river fish to a migratory image, life could have developed even with a relatively stable river flow regime, which includes migratory fish for breeding. [...]
To protect a number of migratory fish, hatcheries are very important. At such plants, usually built at the mouths of large rivers or at dams, producers are caught and artificial insemination is carried out. The larvae of fish obtained from eggs are kept in growth ponds, and then young juveniles are released into rivers or reservoirs. Billions of juveniles are grown annually in such farms in Russia, which is of great importance in the reproduction and restoration of valuable fish species: sturgeon, salmon, some whitefish and other migratory and some semi-migratory fish, such as pike perch. [...]
In addition to these institutions, basin fisheries research institutes conduct research in each fisheries basin. On inland waters, the All-Union Research Institute of Pond Fisheries (VNIIPRH), part of the All-Union Scientific and Production Association for Fisheries (VNPO for Fish Farming), UkrNIIIRKh and other scientific organizations in many Union republics, conducts research [...]
Kutum (Rutilus frissi kutum Kamensky) is a migratory 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; at present it is found only in the river. Southern Bug.[ ...]
Mass tagging and tracing of fish carrying ultrasonic transmitters showed that the lower and upper spawning grounds are used by producers of one local herd, which do not go beyond its range during feeding and wintering. The approach to spawning grounds is carried out either in autumn (winter fish) or in spring (spring). The stereotype of behavior of producers that spawn in the river does not differ from that described for typically migratory fish. [...]
Wintering migrations are expressed both in migratory and semi-migratory, and in marine and freshwater fish. In migratory fish, wintering migration is often, as it were, the beginning of spawning. Winter forms of migratory fish move from feeding places to the sea for wintering in rivers, where they concentrate in deep holes and winter in a sedentary state, usually without feeding. Wintering migrations take place among migratory fish in sturgeon, Atlantic salmon, Aral barbel and some others. Wintering migrations of many semi-migratory fish are well expressed. In the North Caspian Sea, the Aral Sea and the Sea of \u200b\u200bAzov, adult roach, ram, bream, zander and some other semi-migratory fish, after the end of the feeding season, move to the lower reaches of the rivers to wintering places. [...]
The decrease in 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.) compel researchers to work intensively on issues of fish breeding. Hydro-construction on rivers causes such great disruption of their regimes that many migratory fish cannot use old spawning places in rivers. The lack of proper external conditions precludes the breeding of migratory fish. [...]
At the same time, acclimatized fish species appeared: sabrefish, white-eyed, carp, silver carp, rotan, eel, guppy, etc. Now the ichthyofauna of the river. Moscow has 37 species [Sokolov et al., 2000]. Passing fish, as well as fish species that need river conditions with a fast flow, have completely disappeared. Eutrophication-resistant fish are more numerous — inhabitants of stagnant or low-flowing waters. [...]
The main breeding objects at hatcheries were migratory fish: sturgeon, salmon, whitefish, and cyprinids. In spawning-growing farms and hatcheries, semi-migratory and aquatic fish are bred: cyprinids, perchs, etc. [...]
The most important method of increasing the productivity of commercial fish herds is to catch fish when it is in the most salable condition. In most fish, their fat content and fatness varies greatly from season to season. This is especially pronounced in migratory fish making large migrations without food consumption, as well as in fish having a break in nutrition during wintering. [...]
Acclimatization of fish is widely deployed in our country. The incentive to such events is the increasing demand for commercial fish. In order to acclimatize, the ichthyofauna of some reservoirs (lakes Sevan, Balkhash, Aral Sea) is reconstructed by introducing valuable fish species, new species of fish are populated by newly created reservoirs (reservoirs), etc. In addition, sturgeons are acclimatized in ponds and generally in reservoirs with slower runoff. We are convinced that almost all migratory fish (living in sea and fresh water) can be transferred to fresh water - to ponds. [...]
Hundreds and thousands of kilometers upstream annually rush migratory fish - herring, salmon, sturgeon, and cyprinids. [...]
The fourth type of migration cycles is characteristic of a number of local populations of migratory fish of lakes and reservoirs that have mastered 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 there are also found groups of winter individuals leaving for spawning areas in the fall, that is, performing wintering and spawning migration. [...]
All salmonids, both those belonging to the genus Salmo and to the genus Oncorhynchus, are spawning fish in the fall (with the exception of the Gogchin trout above). None of them breed in sea water; For spawning, all salmon enter rivers: even malolen water is lethal to spermatozoa and eggs even in small quantities, thus hindering the possibility of fertilization. Some salmon are salmon, migratory salmon, Salmo trutta L. and Caspian and Aral salmon and all Far Eastern salmon are typical migratory fish living in the marine environment and entering rivers only for breeding purposes, others are lake salmon trout (Salmo trutta lacustris) , the brook forms of Salmo trutta and its subspecies, which form trout morphs, are aquatic and live all the time in a fresh environment, only making small movements from feeding places to spawning places. In some cases, typical migratory fish form or have formed in the past forms that constantly live in fresh water. To which belong: Salmo salar morpha relictus (Malmgren) - salmon, lake forms Oncorhynchus nerka, river form Salmo (Oncorhynchus) masu. All these freshwater morphs differ from their marine counterparts in a smaller size and a slower growth rate. This is already the influence of fresh water, as we will see below, on typical migratory salmon because they have to live in fresh water. [...]
The adaptive value of dwarf males permanently living in rivers in migratory fish is to provide a population of a larger population and greater reproductive ability with a lower feed base than if the males were large, migratory. [...]
The physiological characteristics of the migratory state are best studied in migratory fish using the example of Yshdroma spawning migrations. In these fish, as well as lampreys, spawning migration incentives arise after a long (from 1 to 15-16 years) period of marine life. Migration behavior can form in different seasons and with a different state 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 For spawning grounds, fat reserves are reduced, which reflects a high level of energy expenditures for the movement and maturation of sex products, and in this case there are differences between spring and winter races: spring, entering rivers in the spring, shortly before spawning, the fat content is not very high. [ ...]
A sub-option of type III migrations are displacements. winter ecological groups of local herds of migratory fish breeding in spring, but entering rivers in areas of reproductive biotopes in the autumn of the previous year. [...]
A method is also widespread when commercial fish spawning occurs in artificial reservoirs, juveniles grow up to the slope stage and then release into natural reservoirs. In this way, the artificial reproduction of semi-aisle commercial fish, such as bream, common carp, and others, is built in fish farms of the Volga delta, the lower reaches of the Don, Kuban, and several 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 eggs and milk from producers, fertilization of eggs, its incubation to the release of viable young from a hatchery in a natural reservoir. Thus, breeding is carried out mainly of migratory fish - sturgeon, for example, on the Kura, salmon in the north and the Far East, whitefish and some others (Cherfas, 1956). With this type of dilution, it is often necessary to keep the producers to mature their sexual products, and sometimes to stimulate the return of the sexual products by injection of the pituitary hormone. Caviar incubation is carried out in special fish-breeding machines installed in a special room or exhibited in the riverbed. Juveniles usually grow to a downward state in special pools or ponds. At the same time, juveniles are fed with artificial or natural feed. Many hatcheries have special workshops for growing live food - crustaceans, small-bristle worms, bloodworms. The efficiency of the hatchery is determined by the life stability of the fry released from the plant, i.e., the value of the commercial return. Naturally, the higher the applied biotechnology of fish farming, the higher it is. efficiency. [...]
The first step towards resolving this issue is to delay the duration of the freshwater way of life of migratory fish. In relation to sturgeon fish (sturgeon, stellate stellate and beluga), this is already being successfully implemented. The second and most difficult stage is the management of the breeding process. [...]
Daily food intake also depends on age: juveniles usually eat more than adults and old fish. In the pre-spawning period, feeding intensity decreases, and many marine and especially migratory fish eat little or completely stop eating. The daily rhythm of nutrition also varies in different fish. In peaceful fish, especially planktonivores, nutritional breaks are small, while in predatory fish they can last more than a day. In cyprinids, two maxima of feeding activity are observed: in the morning and in the evening. [...]
In the same area, the whole life cycle of vendace and smelt takes place, which in their migrations, with the exception of the 4th Tsucherechensky, does not extend beyond the delta. Their spawning occurs in tundra rivers associated with lips and river deltas. Part of the vendace spawns directly in the bays of the bay (New Port area). Of the other fish, ruffs and burbot deserve attention, the stocks of which are underutilized. [...]
Of course, the temperature regime is a leading factor determining the normal course of maturation of sexual products of fish, the beginning and duration of spawning, and its effectiveness. However, in natural conditions, for the successful reproduction of most freshwater and migratory fish, the hydrological regime is also important, or rather, the optimal combination of temperature and level regimes of the reservoir. It is known that spawning of many fish begins when water rises rapidly and, as a rule, coincides with the peak of the flood. Meanwhile, the regulation of the flow of many rivers dramatically 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 remained in the lower pools of the waterworks. [...]
It should be noted that the herds or ecological races into which the subspecies breaks up often have different breeding sites. In semi-migratory and migratory fish, so-called seasonal races and biological groups are formed that have similar biological significance. But in this case (among herds and races) the “order” of reproduction is ensured even more by the fact that it is fixed hereditarily. [...]
An almost extinct species formerly widespread along the entire coast of Europe (Berg, 1948; Holöik, 1989). Met in the north before Murman (Lagunov, Konstantinov, 1954). Passing fish. In Lake Ladoga and Onega, there may have been a residential form (Berg, 1948; Podushka, 1985; Kudersky, 1983). Very valuable species, in the late XIX - early XX centuries, which had commercial value. It is included in the Red Books of 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 of 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 open seas, and only 10% of the catch is in 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 the inland water bodies of the country especially important for fish farming. The negative impact of hydraulic structures of hydroelectric power plants on fisheries is manifested in violations of the natural migration paths of migratory fish (sturgeon, salmon, whitefish) to spawning grounds and a sharp decrease in flood discharge of water, which does not provide irrigation of spawning grounds of semi-migratory fish in the lower reaches of the rivers (common carp, pike perch, bream) . Pollution of fish stocks in inland waters is also affected by pollution of water basins with oil product discharges and effluents from industrial enterprises, timber rafts, water transport, fertilizer discharges and chemical pest control agents. [...]
First of all, due to elementary populations, the population of this herd is of different quality. Imagine, for example, a roach in the Northern Caspian or other semi-migratory or migratory fish would not have such different quality, and, say, all fish would mature at the same time and therefore all would immediately rush into the Volga delta to spawn. In this case, there would be overpopulation at the places of spawning and the death of producers due to a lack of oxygen. But there is no such overpopulation and it cannot be, since in reality the spawning course is sufficiently stretched, and fish can use limited breeding places in turn, ensuring the continuation of the life of this subspecies or herd. [...]
Pasture fish farming has large reserves, based on the receipt of marketable products through the improvement and productive use of the natural food supply of lakes, rivers, reservoirs, fish acclimatization and the directed formation of ichthyofauna, artificial breeding and rearing of young migratory fish (sturgeon, salmon) to restore their stocks. [...]
Intensive human activity associated with the development of industry, agriculture, water transport, etc. in some cases negatively affected the state of fishery reservoirs. Almost all of the largest rivers in our country: the Volga, Kama, Urals, Don, Kuban, Dnieper, Dniester, Daugava, Angara, Yenisei, Irtysh, Syr Darya, Amu Darya, Kura and others. Are partially or fully regulated by dams of large hydroelectric power stations or irrigation hydroelectric facilities. Almost all migratory fish — sturgeon, salmon, whitefish, cyprinidae, herring — and semi-migratory — perch, cyprinidae, etc. — lost their natural spawning grounds that had developed over the centuries. [...]
The salt composition of water. Under the salt composition of water is understood as a combination 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 salted (more than 47% o). Sea water contains mainly chlorides, and fresh water contains carbonates and sulfates. Therefore, fresh water is hard and soft. Too desalinated, as well as saline, water bodies are unproductive. Salinity of water is one of the main factors determining the habitat of fish. Some fish live only in fresh water (freshwater), while others live in marine (marine). Passing fish replace sea water with 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.
The structure and physiological characteristics of fish
Table of contents
Body shape and modes of movement
The skin of fish
Digestive system
Respiratory system and gas exchange (New)
Circulatory system
Nervous system and sensory organs
Endocrine glands
Fish poisoning and poisoning
The body shape of fish and ways to move fish
The shape of the body should provide the fish with the ability to move in water (a medium much denser than air) with the least expenditure of energy and at a speed corresponding to its vital needs. The body shape that meets these requirements was developed in fish as a result of evolution: a smooth, without protrusions body, covered with mucus, facilitates movement; no neck; a pointed head with pressed gill covers and clenched jaws cuts through the water; the fin system determines movement in the right direction. According to lifestyle, up to 12 different types of body shape are distinguished.
Fig. 1 - lard; 2 - mackerel; 3 - bream; 4 - moon fish; 5 - flounder; 6 - eel; 7 - needle fish; 8 - herring king; 9 - ramp; 10 - hedgehog fish; 11 - body; 12 - makrus.
Arrow-shaped - the snout bones are elongated and pointed, the body of the fish has the same height along the entire length, the dorsal fin is assigned to the tail fin and is located above the anal fin, which creates an imitation of the plumage of an arrow. This form is typical of fish that do not travel long distances, are kept in ambush and develop high speeds for a short period of time due to the push of the fins when they are thrown to prey or away from the predator. These are pikes (Esox), sharks (Belone), etc. Torpedo-shaped (it is often called spindle-shaped) is characterized by a pointed head, a rounded, oval-shaped cross-section of the body, a refined tail stem, often with additional fins. It is peculiar to good swimmers, capable of prolonged movement - tuna, salmon, mackerel, sharks, etc. These fish are capable of swimming for a long time, so to speak, at a cruising speed of 18 km per hour. Salmon are able to make two-three meter jumps while overcoming obstacles during spawning migrations. The maximum speed that a fish can develop is 100-130 km per hour. This record belongs to a sailing fish. Symmetrically compressed laterally, the body is strongly laterally compressed, high with a relatively short length and high. These are fish of coral reefs - bristles (Chaetodon), thickets of bottom vegetation - scalars (Pterophyllum). This body shape helps them easily maneuver among obstacles. Some pelagic fish, which need to quickly change their position in space for disorientation of predators, have a symmetrically compressed lateral body shape. The moon-fish (Mola mola L.) and bream (Abramis brama L.) have the same body shape. The body is asymmetrically compressed laterally - the eyes are shifted to one side, which creates an asymmetry of the body. It is peculiar to benthic sedentary fish of the order Flounder, helping them to camouflage well at the bottom. In the movement of these fish an important role is played by the wave-like bending of the long dorsal and anal fins. The body flattened in the dorsoventral direction is strongly compressed in the dorso-abdominal direction, as a rule, the pectoral fins are well developed. Sedentary bottom fish have such a body shape - most stingrays (Batomorpha), monkfish (Lophius piscatorius L.). A flattened body disguises fish in the bottom, and the eyes located above help to see prey. Acne-shaped - the body of the fish is elongated, rounded, having the form of an oval in cross section. The dorsal and anal fins are long, there are no ventral fins, and the caudal fin is small. It is characteristic of such bottom and bottom fish, such as eel-like (Anguilliformes), which move, bending the body laterally. Ribbon-shaped - the body of the fish is elongated, but unlike the acne-shaped form, it is strongly compressed from the sides, which provides a large specific surface and allows the fish to inhabit the water column. The nature of their movement is the same as that of fish of an acrid form. This body shape is characteristic of saber fish (Trichiuridae), the herring king (Regalecus). Macro-shaped - the body of the fish is high in the front part, narrowed from the back, especially in the tail section. The head is large, massive, eyes are large. It is peculiar to deep-water sedentary fish - Macrus (Macrurus), chimera-like (Chimaeriformes). Asterolepid (or body-shaped) - the body is enclosed in a bone shell, which provides protection from predators. This body shape is characteristic of benthic inhabitants, many of which are found in coral reefs, for example for bodies (Ostracion). The spherical shape is characteristic of some species from the order Tetraodontiformes - fish-ball (Sphaeroides), hedgehog-fish (Diodon), etc. These fish are poor swimmers and move with the help of undulating (wavy) movements of fins over short distances. In case of danger, the fish inflate the air sacs of the intestine, filling them with water or air; at the same time, the thorns and spikes on the body are straightened, protecting them from predators. The needle-shaped body shape is characteristic of marine needles (Syngnathus). Their elongated body hidden in the bone shell imitates the leaves of the zoster, in the thickets of which they live. Fishes are deprived of lateral mobility and are moved using the undulating (wavy) action of the dorsal fin. Often there are fish whose body shape resembles at the same time various types of forms. To eliminate the unmasking shadow on the fish’s belly, which occurs when illuminated from above, small pelagic fishes, for example, herring (Clupeidae), coughfish (Pelecus cultratus (L.)], have a pointed, laterally compressed abdomen with a sharp keel. In large mobile pelagic predators, mackerel (Scomber), swordfish (Xiphias gladius L.), tuna (Thunnus) - the keel usually does not develop.Their way of protection is speed of movement, but not masking.In the bottom fish, the cross-sectional shape approaches the isosceles trapezoid facing large base down, which eliminates the appearance of those nor on the sides when illuminated from above, so most bottom fish have a wide flattened body.
SKIN, SCALING AND LIGHTING BODIES
Fig. The shape of fish scales. a - placoid; b - ganoid; in - cycloid; g - ctenoid
Placoid - the oldest, preserved in cartilaginous fish (sharks, stingrays). It consists of a plate on which the spike rises. Old scales are discarded, new ones appear in their place. Ganoid - mainly in fossil fish. The scales have a rhombic shape, are closely articulated with one another, so that the body is enclosed in a shell. Scales do not change over time. The name for its scales is due to ganoin (a dentin-like substance), a thick layer lying on the bone plate. Among modern fish, it has armored pikes and multi-feathers. In addition, it is found in sturgeons in the form of plates on the upper lobe of the caudal fin (fulcra) and bugs scattered throughout the body (a modification of several merged ganoid scales). Gradually changing, the scales lost their hanoin. Modern bony fish no longer have it, and the scales consist of bone plates (bone scales). These scales can be cycloid - rounded, with smooth edges (cyprinids) and ctenoid with a serrated posterior edge (perch). Both forms are related, but cycloid as more primitive found in low-organized fish. There are cases when, within the same species, males have ctenoid, and females have cycloid scales (flounders of the genus Liopsetta), or even one individual has scales of both forms. The size and thickness of the scales in fish vary greatly, from microscopic scales of common eel to very large, palm-sized scales of a three-meter barbel, living in Indian rivers. Only a few fish have no scales. For some, it merged into a continuous motionless carapace, like a bodywork, or formed rows of closely connected bone plates, like sea horses. Bone scales, like ganoid ones, are constant, do not change, and only increase annually in accordance with the growth of fish, and distinct annual and seasonal marks remain on them. The winter layer has more frequent and thinner strata than the summer layer, 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 silver guanine crystals. 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 flakes with holes that form a lateral line - one of the most important sensory organs. The amount 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 for different species, even closely related; in some cases, their intraspecific differentiation (age, gender) is determined. Many fish, including cyprinids, form the so-called fear substance (ichthyopterin), which is released into the water from the body of a wounded individual and is perceived by its relatives as a signal that signals danger. The skin of the fish regenerates quickly. Through it occurs, on the one hand, the partial release of the final metabolic products, 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 a large role as a receptor surface: it contains thermo-, baro-, chemo- and other receptors. In the thickness of the corium, 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-tail muscles.
Muscular system and electrical organs
The muscle system of fish, like other vertebrates, is divided into the muscle system of the body (somatic) and internal organs (visceral).
In the first, the muscles of the body, head and fins are secreted. 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 lymph vessels are located in the connective tissue layer of the 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 into the dorsal (upper) and abdominal (lower) parts by the longitudinal connective tissue layer.
Fig. 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. Myomers are most clearly seen in fish larvae, while their bodies are transparent. The muscles of the right and left sides, alternately contracting, bend the caudal region 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, sturgeon and bony have a direct lateral superficial muscle (m. Rectus lateralis, m. Lateralis superficialis). Salmon have a lot of fat stored in it. On the lower side of the body stretches the rectus abdominis muscle (m. Rectus abdominalis); some fish, such as eels, do not have it. Between it and the rectus 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 greatest accumulation of muscles 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.
Distinguish striated (acting largely arbitrary) and smooth muscles (which act regardless of the will of the animal). The striated muscles of the body (trunk) and the muscles of the heart are striated. The trunk muscles can contract quickly and severely, but they soon become tired. A feature of the structure of the heart muscles is not the parallel arrangement of isolated fibers, but the branching of their ends and the transition from one bundle to another, which determines the continuous operation of this organ. Smooth muscles also consist of fibers, but are much shorter and not detecting transverse striation. These are muscles of the internal organs and walls of blood vessels, having peripheral (sympathetic) innervation. The striated fibers, and therefore the muscles, are divided into red and white, differing, 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 (respiration rate, glycogen content, etc.). Fibers of red muscle (m. Lateralis superficialis) - narrow, thin, intensely blood supply, 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 white. In the muscle of the heart (red) there is little glycogen and many enzymes of aerobic metabolism (oxidative metabolism). It is characterized by a moderate rate of contraction and is tired more slowly than white muscles. In wider, thicker, lighter white fibers m. myoglobin lateralis magnus is small, there is less glycogen and respiratory enzymes in them. Carbohydrate metabolism occurs predominantly anaerobically, and the amount of energy released is less. Individual cuts are quick. Muscles contract and tire faster than red ones. They lie more deeply. Red muscles are constantly active. They provide long and continuous operation of the organs, support the constant movement of the pectoral fins, provide bends of the body during swimming and turns, the continuous work of the heart. With fast movement, throws white muscles are active, with slow - red muscles. 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 prolonged migrations, in addition to the red lateral muscles, there are additional red fibers in the white muscles. The bulk of muscle tissue in fish are white muscles. For example, in asp, roach, and sabrefish, they account for 96.3; 95.2 and 94.9%, respectively. White and red muscles differ in chemical composition. Red muscle contains more fat, while white muscle contains 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. For example, in carp, grown on natural food, the diameter of the muscle fiber is (microns): in fry - 5 ... 19, underyearlings - 14 ... 41, two-year-olds - 25 ... 50. The trunk muscles form the main share of fish meat . The meat yield as a percentage of total body weight (meatiness) is not the same for different species, and for individuals of one species it differs depending on gender, conditions of keeping, etc. Fish meat is digested faster than meat of warm-blooded animals. It is often colorless (pikeperch) or has shades (orange - in salmon, yellowish in sturgeon, etc.), depending on the presence of various fats and carotenoids. Albumin and globulin make up the bulk of fish muscle proteins (85%); in all, 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 one species, the quantity and chemical composition of meat depend on the nutritional conditions and physiological state of the fish. In 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, and the skin - by 2.5 times. Muscles are hydrated - the dry matter content is more than halved; fat and nitrogenous substances practically disappear from the muscles - the fish loses up to 98.4% of fat and 57% of protein. Environmental features (primarily food and water) can greatly change the nutritional value of fish: in marshy, muddy or oil-contaminated ponds, 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 tissue, which can be used to judge the content of full 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 muscle proteins of bony fish, proteins account for: sarcoplasmas 20 ... 30%, myofibrils - 60 ... 70, stroma - about 2%. The whole variety of body movements provides the work of the muscular system. It mainly provides heat and electricity in the body of fish. An electric current is generated during a nerve impulse through the nerve, during contraction of myofibrils, irritation of photosensitive cells, mechanochemical receptors, etc.
Peculiarly altered muscles are electrical organs. These organs develop from the rudiments of the striated muscle and are located on the sides of the body of the fish. They consist of many muscle plates (electric eel has about 6000), transformed into electrical plates (electrocytes), interbedded by gelatinous connective tissue. The lower part of the plate is negatively charged, the upper - positively. Discharges occur under the action of impulses of the medulla oblongata. Due to the discharges, water decomposes into hydrogen and oxygen, therefore, for example, small inhabitants - mollusks, crustaceans, attracted by more favorable respiration conditions, accumulate near the electric fish in the tropic overland waters. Electric organs can be located in different parts of the body: for example, at the stingray of a sea fox - on the tail, at the electric catfish - on the sides. By generating electric current and perceiving lines of force distorted by objects encountered on the path, the fish orient themselves in the stream, detect obstacles or prey from a distance of several meters, even in muddy water. In accordance with the ability to generate electric fields, fish are divided into three groups: 1. Strongly electric species - have large electric organs generating discharges from 20 to 600 and even 1000 V. The main purpose of the discharges is attack and defense (electric eel, electric slope, electric catfish). 2. Weak-electric species - they have small electric organs generating discharges with voltage less than 17 V. The main purpose of the discharges is location, signaling, orientation (many mormirids, hymnotids, some slopes that live in muddy rivers of Africa). 3. Non-electric species - do not have specialized bodies, but have electrical activity. The discharges generated by them spread over 10 ... 15 m in seawater and up to 2 m in fresh water. The main purpose of the generated electricity is location, orientation, alarm (many marine and freshwater fish: for example, horse mackerel, atherin, perch, etc.).
