Types of fish migrations. migratory behavior of fish. Salmon migrations

Fish migrations are periodic mass movements. Knowledge of the timing and directions of migrations, the patterns to which they are subject, is important practical value. Settled image few fish lead a life (fish of coral reefs, some gobies, etc.). In most fish, migrations are certain links life cycle, inextricably linked.

There are horizontal and vertical migrations. Horizontal migrations can be passive or active. During passive migrations, eggs and larvae are carried by currents from spawning areas to feeding areas. Thus, eggs and larvae of Atlantic cod spawning near the Lofoten Islands (Norway) drift in the Gulf Stream jets into the Barents Sea; European eel larvae Sargasso Sea drift within 2.5–3 years to the shores of Europe, etc.

Active migrations, depending on the purpose, are: 1) spawning; 2) feed; 3) wintering.

The length of migrations varies considerably. Some species make small movements (flounder), others can migrate thousands of kilometers (eel, salmon).

Spawning migrations (movements from feeding or wintering areas to spawning grounds).

In semi-anadromous fish, migrations are distinguished: 1) anadromous, fish go to spawn from the seas to rivers (salmon, sturgeon, etc.); 2) catadromous - from rivers to the sea (river eel, some types of gobies, galaxian fish).

In the process of evolution, some anadromous fish experienced intraspecific differentiation, which led to the formation of seasonal races - winter and spring ( river lamprey, Atlantic salmon, some sturgeons, etc.). Fish of the spring race enter the rivers with developed gonads shortly before spawning, while those of the winter race enter the rivers in autumn with undeveloped sexual products, spend in the river from several months to a year and breed on next year. In winter races, spawning migrations are combined with wintering ones. During spawning migrations, fish usually do not feed or feed poorly, and the necessary energy resources for movement and development of the sex glands are accumulated in advance in the form of fat.

The reasons for anadromous migrations are primarily related to the fact that in fresh waters the conditions for reproduction and the survival of eggs and larvae are more favorable than in the sea.

Many marine and freshwater species make spawning migrations to the shores (cod, Atlantic herring, whitefish, etc.), and some of them go to great depths for spawning (sea flounder, big-eyed zuban).

Feeding migrations (movements from breeding or wintering grounds to feeding grounds). For many fish, feeding migrations begin already at the stage of eggs. The transfer of pelagic eggs and larvae from spawning grounds to nursery grounds is a passive feeding migration. A large number of eggs and larvae freshwater fish carried in rivers by currents from spawning grounds to feeding lakes (whitefish, etc.).

Polycyclic fish after breeding make feeding migrations of various lengths. Atlantic salmon and sturgeon, after breeding in the rivers, go to feed in the sea. Atlantic herring spawns off the coast of Norway, after breeding migrates to fattening in the Iceland area and further north. Sometimes feeding migrations are combined with spawning ones (Azov anchovy). Wintering migrations (movements from breeding or feeding grounds to wintering grounds). Wintering migration begins with fish that are physiologically prepared, having reached a certain fatness and fat content. Yes, hamsa Sea of ​​Azov after feeding, it migrates to the Black Sea in autumn and winters at a depth of 100–150 m. Wintering migration can begin only when the fish accumulate a sufficient amount of fat (at least 14%). Fish not prepared for migration continue to feed and do not migrate. In anadromous fish, wintering migrations are often the beginning of spawning ones. Winter forms of some of them, after fattening in the sea, enter rivers in autumn and winter in them (river lamprey, sturgeons, Atlantic salmon, etc.). Some species living in the Volga at autumn cooling migrate to the lower reaches of the river and lie in holes (bream, carp, catfish, pike perch).

In addition to horizontal migrations, fish are characterized by vertical migrations. Spawning vertical migrations are performed by the Baikal golomyanka, which, before spawning larvae, emerges from a depth of about 700 m into the surface layers of water and dies after reproduction.

Many marine and freshwater species make diurnal vertical migrations, moving after food objects (herring, sprat, sprat, mackerel, horse mackerel, vendace, etc.). Juveniles of many fish species also migrate vertically, following food organisms.

In winter, many pelagic fish sink into deeper and less chilled layers than during feeding and form large, slow-moving aggregations (herring, Azov anchovy, etc.).

Knowledge of the patterns of fish migration is important in the organization of rational fishing. One of the methods for studying migrations is labeling. Marking can be individual (each mark has its own number) and group (all fish are marked equally). Tagging allows you to study the migration routes, determine the speed of fish movement, population size, and the efficiency of fish farming.

20.PLACE OF FISH IN WATER BIOCENOSES

The migration of fish in the river is its time-established mass movements in the reservoir. Occurs, according to experts, all year round and, knowing its causes, patterns, the angler can calculate where in this moment It is better to catch one or another type of fish.

Fish have been proven to live by trying to expend less energy. Therefore, its migratory movements may be associated with a desire to find conditions under which its energy consumption will be minimal. Another important reason for moving from place to place may be a sense of anxiety for life - a simple flight to where some predator can not get it.

When migrating, fish can make three types of movements, differing in direction: along the coast; perpendicular to the shore down/up in depth. All these types are conditional, since they are practically not observed in their pure form, but represent a movement that is complex along the trajectory, in which one of the indicated directions prevails.

The migration of fish along the coast allows the fish to quickly change living conditions and is “used” by it for fast, emergency movements. Moving perpendicular to the shore, individuals save time resources, which is observed by many anglers after, for example, their “fright” from the silhouette of a fisherman they saw. Ascent/dive when moving vertically is used by fish to solve some of their problems less often, it has a larger “bouquet” of reasons.

Causes of fish migrations

One of the main reasons that cause migratory movements of fish in the river is a change in the concentration of oxygen in the water and other gases they need. Fish tend to those places where there are more of them, as they contribute to an increase in the feeding activity of fish.

Another reason is the temperature of the water, which affects the mobility of the fish. Especially it concerns low temperatures when you have to spend a lot of energy on movement. Bad for fish and temperatures above optimal for them, as they reduce food activity.

Among the reasons for migration is the speed of the flow in the river of water. There are 2 options here: a lot of food in the stream, then it more than compensates for the energy costs of moving against the current; with a small amount of food, it determines the disadvantage for the fish to be in the stream.

Fish migration along the coast

The distances of such migrations can be different: from hundreds of meters to many hundreds of kilometers. Their most striking example is the movement of fish (more often uplift in the direction of the sources of rivers) before spawning and after the process of spawning.

Spawning migrations are expected by most fishermen, and when they advance on the banks of some domestic rivers, sometimes there is nowhere to stick with their gear. Such movements are usually short in time and can occur within 1-2 weeks. There is also a high density of fish in the flock, which almost always ensures decent catches.

The reason for the pre-spawning migrations of fish is always the same - faster warming of water in the upper reaches of the rivers. Knowing the “favorite” temperature for spawning of any fish, one can always roughly calculate the specific dates for the start of its movements in a given river to spawning grounds.

Coastal movement of fish is also possible by the type of its entry from large reservoirs into rivers for winter and summer. Their main reason is a change in the food supply of places, and the differences from spawning migrations are more later dates, the need to move quietly, which saves energy.

Fish migrations perpendicular to the shore

The nature of such movements: from shallow, coastal places to remote from land and deeper. This is due to changes in water temperature, oxygen concentration in it, illumination, food supply, and a decrease in biological hazard.

The most common types of transverse migration of fish are their diurnal waste-approaches to the shore. Moreover, there may be several such movements during the day and night.

This type of migration is typical for bream, which is successfully caught near the coast at night, and during the day it goes to rest further and deeper. This may apply to roach, silver bream, burbot. For fish of the "day" type, approaches to the shore during the day and away from it at night are characteristic.

One of the reasons for the exit of "deep" fish to the shore may be the massive flight of various insects. Given that the appearance of the latter usually occurs closer to the coast, this migration can be attributed to the transverse type.

Fish migrations vertically

The most likely reason for such migrations is the movement of food. Although it is more pronounced in small fish, but large individuals are usually less ready for it. This is explained by the greater biological hazard in the water column and the lack of places in it where you can quickly hide from danger.

In addition to feeding, vertical movements of fish can be caused by temperature fluctuations and changes in oxygen content on different levels by depth.

All of the above is a desire to help fishermen evaluate places more realistically. good fishing in different time year, at different conditions water and air.

Specially for- V.A.N.

Fish migrations are periodic mass movements. Knowledge of the timing and directions of migrations, the patterns to which they are subject, is of great practical importance. Few fish lead a settled way of life (fish of coral reefs, some gobies, etc.). In the majority of fish, migrations are certain parts of the life cycle that are inextricably linked.

There are horizontal and vertical migrations. Horizontal migrations can be passive or active. During passive migrations, eggs and larvae are carried by currents from spawning areas to feeding areas. Thus, eggs and larvae of Atlantic cod spawning near the Lofoten Islands (Norway) drift in the Gulf Stream jets into the Barents Sea; larvae of the European eel from the Sargasso Sea drift for 2.5–3 years to the shores of Europe, etc.

Active migrations, depending on the purpose, are: 1) spawning; 2) feed; 3) wintering.

The length of migrations varies considerably. Some species make small movements (flounder), others can migrate thousands of kilometers (eel, salmon).

Spawning migrations (movements from feeding or wintering areas to spawning grounds).

In semi-anadromous fish, migrations are distinguished: 1) anadromous, fish go to spawn from the seas to rivers (salmon, sturgeon, etc.); 2) catadromous - from rivers to the sea (river eel, some types of gobies, galaxian fish).

In the process of evolution, some anadromous fish experienced intraspecific differentiation, which led to the formation of seasonal races - winter and spring (river lamprey, Atlantic salmon, some sturgeons, etc.). Fish of the spring race enter the rivers with developed gonads shortly before spawning, while those of the winter race enter the rivers in autumn with undeveloped sexual products, spend in the river from several months to a year and breed the next year. In winter races, spawning migrations are combined with wintering ones. During spawning migrations, fish usually do not feed or feed poorly, and the necessary energy resources for movement and development of the sex glands are accumulated in advance in the form of fat.

The reasons for anadromous migrations are primarily related to the fact that in fresh waters the conditions for reproduction and the survival of eggs and larvae are more favorable than in the sea.

Many marine and freshwater species make spawning migrations to the coast (cod, Atlantic herring, whitefish, etc.), and some of them go to great depths for spawning (sea flounder, big-eyed zuban).

Feeding migrations (movements from breeding or wintering grounds to feeding grounds). For many fish, feeding migrations begin already at the stage of eggs. The transfer of pelagic eggs and larvae from spawning grounds to nursery grounds is a passive feeding migration. A large number of eggs and larvae of freshwater fish are carried in rivers by currents from spawning grounds to feeding lakes (whitefish, etc.).

Polycyclic fish after breeding make feeding migrations of various lengths. Atlantic salmon and sturgeon, after breeding in the rivers, go to feed in the sea. Atlantic herring spawns off the coast of Norway, after breeding migrates to fattening in the Iceland area and further north. Sometimes feeding migrations are combined with spawning ones (Azov anchovy). Wintering migrations (movements from breeding or feeding grounds to wintering grounds). Wintering migration begins with fish that are physiologically prepared, having reached a certain fatness and fat content. Thus, the anchovy of the Sea of ​​Azov migrates to the Black Sea after feeding in autumn and winters at a depth of 100–150 m. Wintering migration can begin only when the fish accumulate a sufficient amount of fat (at least 14%). Fish not prepared for migration continue to feed and do not migrate. In anadromous fish, wintering migrations are often the beginning of spawning ones. Winter forms of some of them, after fattening in the sea, enter rivers in autumn and winter in them (river lamprey, sturgeons, Atlantic salmon, etc.). Some species living in the Volga during the autumn cooling migrate to the lower reaches of the river and lie in pits (bream, carp, catfish, pike perch).

In addition to horizontal migrations, fish are characterized by vertical migrations. Spawning vertical migrations are performed by the Baikal golomyanka, which, before spawning larvae, emerges from a depth of about 700 m into the surface layers of water and dies after reproduction.

Many marine and freshwater species make diurnal vertical migrations, moving after food objects (herring, sprat, sprat, mackerel, horse mackerel, vendace, etc.). Juveniles of many fish species also migrate vertically, following food organisms.

In winter, many pelagic fish sink into deeper and less chilled layers than during feeding and form large, slow-moving aggregations (herring, Azov anchovy, etc.).

Knowledge of the patterns of fish migration is important in the organization of rational fishing. One of the methods for studying migrations is labeling. Marking can be individual (each mark has its own number) and group (all fish are marked equally). Tagging allows you to study the migration routes, determine the speed of fish movement, population size, and the efficiency of fish farming.

N. V. ILMAST. INTRODUCTION TO ICHTHYOLOGY. Petrozavodsk, 2005

AT The life of fish is of great importance for their periodic movements, or migrations. They fall into two categories; passive migrations belong to the first of them, to the second - a to t and v n s e.

Passive migrations are understood as the movement of eggs, larvae and fry of fish with the help of a water current; no effort is expended on the part of the embryos themselves. With active migration, fish move independently in a certain direction, often overcoming significant obstacles (strong oncoming current, river rapids).

Rice. one . The head of a male chum salmon coming from the sea.

BUT-outside; B-outer bones of the skull.

An example of passive migration is the transfer of Norwegian herring larvae. sea ​​current along the coast of Norway from spawning grounds (from the coastal area between Lister and Ålesund). This passive migration, driven by coastal currents, extends for 800-1000 km.

Passively migratory larvae sea ​​eel from spawning grounds (near Bermuda) to the shores of Europe. Brought to great depth larvae move vertically as they grow. When the larvae reach 2.5 cm, they are already at a depth of only about 50 m, here they are picked up by the surface warm current of the Gulfstrom and slowly transferred through the entire huge Atlantic Ocean. This passive journey is made over the course of two years.

In our lower reaches major rivers For example, in the Volga, one can observe the “slope” of many fish juveniles along the river into the sea (in trophically brackish water species).

As for active migrations, they can be stimulated by several reasons.

The first category of such migrations includes movements in search of food. This is how, for example, cods (Gadus callarias) migrate in our North. After the end of spawning, which takes place near the Lofoten Islands, these fish move along the coast of Murman along warm current Gulfstrom, and they feed heavily.

At this time, the blue fish go from the sea to the estuaries for fattening; in autumn, with a cold snap, they again rush to the open sea.

The second category of active migrations includes spawning migrations associated with the reproduction of the species. In the direction of movement, spawning migrations are divided into anadromous (potamodromous), when fish follow for spawning from the seas to rivers, and into catadromous (thalassodromous), during which fish leave rivers for spawning. salt water seas.

Let's take a look at some examples of spawning migrations. When describing herring, it was mentioned that some species, such as, for example, sea herring, make spawning migrations from the pelagic zone to the banks, shoals and fiords; other herrings, such as some Caspian ones, go to rivers to the Volga, Ural. An epoch in the history of studying the migrations of sea herring was the research of the Director of the Biological Station in Helgoland F. Heincke (F. Heincke, 1878, 1898). This zoologist studied the herring races (on an extensive material of up to 6,000 specimens), using the method of biometrics and variation statistics in his work. At the same time, Heinke operated with certain fluctuations in signs. Based on the study of combinations of these characters, it is possible to establish and distinguish between certain permanent types characteristic of certain races. So, for example, Heinke established the presence of a large Icelandic herring, characterized by a large number vertebrae (average 57), short snout, big eyes; the White Sea herring, the Norwegian herring, and others are well distinguishable from it. Each of these races is divided into even smaller races. AT the highest degree It is interesting that each race of herring has its own characteristic spawning grounds, spawning at the time specified for this race under individual conditions of water salinity and temperature. On the example of F. Heinke's research, we can quite clearly see what a great importance carefulsystematic and biometric work to clarify general biological and environmental problems.

AT last years the technique, first introduced into ichthyology by F. Heinke, began to be widely practiced by other researchers with some changes and additions.

Cod was studied similarly to herring. Thanks to the outstanding research of the ichthyologist Johann Schmidt, who reviewed a huge amount of material (up to 20,000 specimens), it was found that the Atlantic cod is heterogeneous in the zone of its vast distribution area. The following remarkable pattern was established: the dependence of the number of vertebrae on temperature conditions. It turned out that the higher the water temperature, the lower the average number of vertebrae. Indeed, cod with painthe largest number of vertebrae is characteristic only of the northern part of the American coast, where the sea temperature is 0 °. The number of vertebrae decreases in fish from north to south on both the American and European coasts. The +10° isotherm pretty accurately limits the distribution area of ​​cod with the smallest number of vertebrae (51.47-51.99) from the north; cod with a moderate number of vertebrae (52.41-53.99) is confined to the area of ​​the 4-5° isotherm.

It was found that cod Baltic Sea isolated and not connected with the Atlantic; Norwegian cod living in the fjords is local, spawning there, etc.

There is no doubt that all these data are of great importance for the accurate study of migrations. Thanks to a detailed study of the morphological features of the species and its numerous races, it is possible to establish in which places of the vast range a certain race spawns, and this, in turn, facilitates the solution of the problem when this race makes its spawning movements.

Rice. 2. Head of a male chum salmon in nuptial attire.

BUT-outside; AT- external bones of the skull;op, r, oh, s. wow - gill cover bones; o-ocular bones; / - frontal bone;et-ethmoid bone; m-maxillary bone;R. t.- intermaxillary bone; j.- supramaxillary bone; d, ar, on-bones of the lower jaw; d-rays of the gill membrane.

Spawning migrations can be clearly studied by studying migratory fish. Of great interest is the study of the spawning movements of our sturgeons.

For example, the Russian sturgeon (Acipenser guldenstaedti) has various types spawning migrations to different rivers. Caspian sturgeons enter the Kura River in the spring, where they spawn at the end of the summer of the same year (in the Mingachevir region); in August, sturgeons return to the sea again. A completely different picture of sturgeon spawning can be observed in the Urals and the Volga. Sturgeons enter the Urals in early spring-March. Most of fish has immature sex products and moves to the places of future spawning, overcoming a long journey of hundreds of kilometers. Having reached Uralsk, the sturgeons lie down for the winter somewhat below this city in the deep pits of the river, inSo called "yatovs", highlightsa large amount of mucus and spend the whole winter in a motionless state.

The coming spring awakens them to a new active life and finds them with fully ripened sexual products. In April, spawning takes place, which lasts several days; after that, the fish go back to the sea. In this way, at In the Volga and Ural sturgeons, spawning migration occurs long before the maturation of the gametes, a year before the actual spawning process. The spawning migrations of beluga, stellate sturgeon, and spike (Acipenser nudiventris) are generally similar to those described by us for sturgeon.

A very vivid picture of spawning migrations can be observed in East Siberian salmonids - chum salmon (Oncorhyrichus keta) and pink salmon (O. gorbuscha). Chum salmon is included for spawning in the river. Amur; most spawning occurs in the tributaries of the Amur or in upstream this river. The speed of chum salmon movement is about 45-47 km per day. There are two “moves” of chum salmon: summer (in at the end of June early July) and autumn (at the end August - early September). Interestingly, summer running fish are smaller than autumn ones. L. S. Berg proposes to consider these biologically separate fixed groups of chum salmon by "seasonal races". Striking are the changes that the chum undergoes during river migration. From the sea, it enters the Amur estuary as a beautiful, slender fish, with silvery scales, with a dark greenish or bronze back. Through short term after staying in fresh water the color of the fish begins to change: the silvery sheen is lost, the body becomes dirty gray, belly black.

Along with the change in color, sharp new morphological changes occur: the end of the snout is bent down in the fish with a hook downwards in the form of a beak (Fig. 1 - 2),huge teeth appear(especially on the premaxillary bones), increases 1.2-1.6 times relative weight bones, the amount of dry matter in muscle tissue decreases (from 31.35 to 14.27% in males and from 33.05 to 15.3% in females), muscle fat disappears, etc.

At one time, Academician A. Middendorf called the described migration of Far Eastern salmonids "a journey without going back." Indeed, the mass of fish after spawning perishes already in the spawning ground, other fish that have begun the reverse movement, in a state of complete relaxation, rush along the river and die in masses. The banks of the river are strewn dead fish, and only a very small part of the spawning chum salmon reaches the mouth of the Amur and its estuary, but even here the exhausted fish die from predators. Until now, there is not a single indication that after the spawning period, the chum salmon again underwent a reverse transformation and acquired its former appearance. Like chum salmon, pink salmon spawns; this fish moves to the spawning grounds in June (the run ends in July). Migration, for example, on the Bolshoy River (in Kamchatka), is of a grandiose nature (Fig. 4). River near the shore on the spit literally boils; in calm weather, the noise from walking and splashing fish is heard for more than 200 m. I. F. Pravdin (1928) says that schools of walking and noisy fish stretch along the river for at least a kilometer; the width of the "front" is not less than 100 m; it can be said without exaggeration that more than one million fish move.

There are several key points to consider when studying spawning migrations.

1. What is the state of the reproductive products of fish at the beginning of spawning. The following pattern can be established: the higher the fish entering it rises along the river, the lower the stage of maturity. It begins its course with the growth of reproductive products, and the lower the spawning grounds are located along the river, the more mature the reproductive products the fish enters the river. In the lower reaches of the Volga, vobla, carp, bream, and shad spawn within the delta. At the beginning of the movement for spawning, these fish have reproductive products at a stage close to final maturity.

In contrast to this category of fish, sturgeon, white salmon, lamprey, etc., passing thousands of kilometers to reach the spawning ground, begin their course along the river, possessing completely immature reproductive products.

2. How far do fish go to spawning grounds. In some cases, the path to spawning grounds for migratory fish can be very long. Thus, the whitefish (Stenodue leucichthys) passesalong the Volga to the Kama and from the Kama to the Belaya, from here to the tributary of the river. Belaya-r. Ufa, making a path of 2,950 km from the mouth of the Volga. Sturgeon pass to the Kama from the mouth of the Volga, making a journey of 2,000 km or more. Zalom herring (Caspialosa kessleri) reach their spawning grounds on the Volga and Kama after a journey of 2,000-2,800 km.

3. What is the speed of migration of the walking fish. Thanks to tagging, it was possible to establish the speed of movement of migratory fish. So, for example, the stellate sturgeon on the Kura travels an average of 22 km per day, and the enormous force of the river current is overcome. If this factor is taken into account, the theoretical average speed of a walking stellate sturgeon reaches almost 100 km per day.Keta on the Amur goes with average speed up to 47 km per day.

All migrations considered by us belong to the category of anadromous.

A striking example of catadromous migration is the spawning movement of eels, excellently studied by Johann Schmidt. An adult eel living in the river basins of the Baltic, German Seas and the Atlantic Ocean, having reached puberty, undertakes a grandiose journey to spawning grounds located in the western tropical part of the Atlantic Ocean in the Bermuda region. On this journey,estimated at several thousand nautical miles, the eel crosses the entire Atlantic Ocean, spawning on great depths(more than 1,000 m).

Peculiar migrations take place when fish travel from more small places in the depths of the sea for the winter. Such migrations include periodic movements of Far Eastern flounders. AT summer time flounders, according to P. Yu. Schmidt (1936), are scattered throughout Peter the Great Bay. With the onset of autumn and with a decrease in temperature, flounders gather in certain places, for example, to the southeast of Askold Island, at depths of 110-250 m. Here they lie in large numbers, buried in silt, probably in several layers, and spend the winter, taking advantage of the conditions of the warm current.

Article on the topic of fish migration

It turns out that the reasons why fish migration, much more complex and diverse than those along which birds make their flights.

First, fish go on long voyages in search of food. Starved and having lost all their strength after spawning, cod undertakes a long transition from the coast of Norway to the north towards the Kola Peninsula, where they come from the Atlantic warm waters currents of the Gulf Stream. They bring plankton with them, which serves as the main food for this ocean fish.

Secondly, salmon or salmon, like cod, with the onset of spawning, are sent from the seas to the rivers, because only in fresh water can they leave the game and hatch fry.

Many species of fish do not change geographic habitats. Near the surface, the fish feed, and in the depths they hatch their young. This type is called vertical. It is caused by the movement of a layer of water containing zooplankton, which passes every year.

When winter comes in the northern latitudes, zooplankton goes to the depths. There the temperature does not fall below four or five degrees above zero Celsius. If zooplankton had remained at the top, they would simply have died from the cold.

For a long time, researchers believed that bottom fish did not migrate. Indeed, flounder leads a sedentary lifestyle. The shape of her body is not well adapted to swimming over long distances. However, as it turned out, the flounder does not stay in one place either. It sails from north to south along the coasts of all of Europe. Schools of flounder reach the Bay of Biscay. There the fish lay their eggs.

For example, vertical migration is performed by the flounder that lives in the North Sea. Schools of fish annually descend into the depths of the ocean, where they lay their eggs. There, in the dark and cold waters, larvae appear. As soon as they gain the ability to move, they begin their journey up.

Observations have shown that a flounder larva only 13 centimeters long swims at least a kilometer per day. While sailing in the warm coastal waters, she manages to grow and take shape. adult fish. For several months, she feeds near the shore, but then again goes into the depths.

fish migration occurs even in lakes. It is known that salmon annually leaves Lake Ladoga for spawning. Lake smelt reproduces similarly.

Some fish annually make their way from the lower reaches of the river to its sources and back. They are called passersby. It has been established that they go to the upper reaches of the river to spawn. The presence of a variety of food in it makes them return to the mouth.

Even river catfish, which live at the bottom of the pools and are known for their sedentary lifestyle, go to shallow water at the time of breeding. They need this in order to leave the eggs in running water rich in oxygen. Then they again hide in their secluded shelters.

Some species migrate only once in their lives. Having reached the age of 1.5 years, the Far Eastern pink salmon returns to the rivers, to the place of its birth, spawns and here, exhausted, dies to become food for the offspring that have been born.